Wood Finishing and Coatings Definitions

To find the term you’re looking for, click on the letter in brackets that the word begins with and scroll down until you find it.

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Abrasion Resistance: A basic durability property. The ability of a coating to withstand wear from mechanical sources (e.g., rubbing or scraping) that tend to wear the surface down. Abrasion resistance should not be confused with mar resistance or hardness, though these properties are closely related. For eample, consider that steel wheels would not last long on the roadway compared to rubber, though steel is much harder.

Accelerated Weathering: A test designed to intensify and accelerate the destructive action of natural outdoor weathering.

Accelerator: Also known as promoter, accelerators are compounds used in polyester and vinyl ester resins to speed up the curing reaction. The accelerator reacts with the catalyst to start the chemical reaction between the resin and styrene monomer and form a cured solid. Accelerator may be added to the resin by the manufacturer or the user will add both the promoter and catalyst when preparing for use. The promoter and catalyst must never be mixed directly together or it will cause an explosive reaction. Cobalt-based compounds are commonly used as a the accelerator.

Acrylic: A family of synthetic resins made from acrylic acids.

Acrylic Latex Paint: Water-reducible paint made with a binder that has acrylic as some portion of the composition. Other modifiers of the binder that may be added to reduce cost or add specific properties include styrene, epoxy, and polyvinyl acetate (PVA).

Acrylic Resin: Clear resin made by the polymerization of acrylic monomers such as acrylates Methyl, Ethyl, Butyl or acrylic acid.

Activator: The curing agent of a two component/compound coating system.

Adhesion: The degree of attachment between a coating and the underlying material to which it is in contact without blistering, flaking, or cracking. The two surfaces are held together by interfacial forces which may consist of valence forces and/or interlocking/mechanical action.

Mechanical Adhesion – An interlocking of two materials because of shape, texture, etc. causing the two materials to remain affixed one to the other. Also known as tooth.

Chemical adhesion – A chemical reaction of two materials that bonds the two together.

Adsorb/Adsorption: Refers to the process of one material attracting and holding molecules of another substance to the surface of its molecules.

Air-assisted airless: An airless spray system operating at lower fluid pressure, typically 300-400 PSI, that uses a small amount of air to shape the spray fan and eliminate the spray tails at the ends of the fan pattern. Used most often in production settings where speed and quality are needed.

Air Cap/Air Nozzle: Perforated housing for directing the atomizing air at the head of an air spray gun. Atomizes the coating and shapes the fan.

Air Drying: A common form of curing a coating in which drying takes place by oxidation or solvent evaporation by simple exposure to air without heat or catalyst.

Air Entrapment: A defect caused by the inclusion of air bubbles in liquid coating film. Often caused by applying the finish too thick, too heavily, or excessive brushing without topping off.

Airless Spray: A spraying system in which coating is atomized using high hydraulic (fluid) pressure rather than compressed air.

Alcohol: A group of solvents of relatively high evaporation rate but with fairly low solvent strength. Commonly used as a solvent in shellac, NGR stains, dyes, inks, and lacquer. Alcohols include Methanol, Ethanol, Isopropanol, n-Butanol, Isooctanol, Methyl Isobutyl Carbinol, Isoamyl Alcohol, Isobutyl Alcohol, Cyclohexanol, and Methyl Cyclohexanol.

NOTE – Methanol is highly toxic both in skin contact as well as by inhalation. Methanol is readily absorbed by the skin and can metabolize to formaldehyde then to formic acid. Methyl alcohol is also known as methanol, methyl hydrate, or wood alcohol.

Aliphatic Hydrocarbons: A class of organic solvents which are composed of open chains of carbon atoms. Aliphatics are relatively weak solvents. Mineral spirits, paint thinner, VM&P naphtha, Stoddard Solvent, petroleum naptha, petroleum distillate, cyclohexane, octane, pentane, nonane, kerosine, gasoline, and heptane, propane, butane, hexane are all aliphatic hydrocarbons.

Alkali: An aqueous liquid which has a pH value of between 7 and 14. A base or caustic material.

Alkyd Resin: A family of synthetic resins formed by the condensation of polyhydric alcohols with polybasic acids. May be regarded as complex polyester (thermoset).

Alligatoring: A form of paint failure in which cracks form on the surface layer. As the name implies, an alligatored surface is one that resembles the hide of an alligator in that it is cracked into regular segments.

Ambient Temperature: Room temperature or the existing temperature of the surroundings.

Amine: Materials often used as curing agents for epoxy coatings.

Aniline (Acid) Dye: Synthetic transparent colors which dissolve in the solvent for which they are formulated (i.e., water, alcohol, or oil). Some dyes are reducible in multiple solvents.

Anti-blocking agent: Additive used to lessen the adhesion of coated surfaces to another surface. Acts by producing a slight roughening of the surface. Are typically finely divided, solid minerals, but some are waxes.

Antioxidant: Compounding material used to retard deterioration of coating films caused by oxidation, heat exposure, etc..

Application: Any process by which a coating is transferred to a surface to be finished. Techniques include padding, wiping, brushing, spraying, and dipping.

Aromatic Hydrocarbons: Aromatic Hydrocarbons derive their name from the “pleasant” odor attributed to many of these substances. The aromatic solvents are produced from the distillation of petroleum or coal tar. A class of relatively strong organic solvents which contain an unsaturated ring of carbon atoms. Not all molecules with ring (loop) structures are aromatic. Examples are Toluene (toluol), Xylene (xylol), Phenol, Benzene, Styrene, Diethylbenzene, Methylnaphthalene, Ethylbenzene.

Asphalt/Asphaltum: A black resinous material of petroleum origin.

Atomization: As the finish exits the nozzle of a spray gun it is broken up using directed air flow to create a fine spray.  A properly atomized spray finish will produce a spray pattern that is mist like in appearance. A poorly atomized coating will consist of larger droplets that may not flow out to form a smooth, level film.

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Barrier Coat: A coating used to isolate a dye, stain, glaze, or topcoat either from the surface to which it is applied or a previous coating for the purpose of increasing adhesion, insuring compatibility, or isolating contamination. Also known as a tie coat.

Base-Color: The first color coat applied during many types of faux finishing techniques.

Binder: The nonvolatile portion of the vehicle of a coating which holds together the pigment particles and attaches them to the substrate.

Bleaching: The fading of a color toward white generally caused by exposure to chemicals or ultraviolet radiation. The use of one of the three wood bleaches to remove natural color, dyes, or water stains from wood.

Bleeding: The diffusion of color matter through a coating from underlying surfaces causing color change. Caused by a common solvency of the topcoat and the dye.

Blistering: The formation of blisters in coating films by the local loss of adhesion and lifting of the film from the underlying substrate.

BLO: Boiled linseed oil. One of the drying oils used to make conversion coatings like varnish.

Blocking: A coating’s tendency to adhere to itself on another freshly coated surface or to other substrates. Causes windows to bind, doors to stick and damage to finished surfaces when they’re contacted before the coating fully cures.

Block Resistance: The ability of a coating to resist sticking to itself when used on two surfaces that come into contact with each other or other surfaces.

Blooming: Unlike blushing, bloom forms after the coating has dried or cured. Presenting as a haze in the film (may be irridescent or bluish like an oil slick) of coating surfaces, it’s caused by the exudation of a component of the coating such as oil plasticizer, uncured oil stain, or non-crosslinked coating constituent when the coated part is exposed to a cycle of heat, humidity, and cooling. Also caused when an acid cured coating (e.g., conversion varnish) is applied over a sealer that contains zinc stearate; the acid and zinc have a chemical reaction as the coating cures (may occur months after application).

Blotch/Blotching: Blotches are random areas on the surface of the wood that have adsorbed more of the dye, stain, or finish compared to other areas. The sharp contrast between dark and lighter areas on the wood surface is usually considered unattractive.

Blushing: A film finish defect which manifests itself as a milky appearance which is generally caused by rapid solvent evaporation or the presence of excessive moisture during the curing process. Blushing can be prevented by slowing down the drying/evaporation rate of the solvents in the coating by adding a retarder. It can be easily corrected by misting the affected surface with a slow evaopating solvent (aka, retarder).

Blush Retarder: A thinner/reducer with slower evaporation properties.

Body: Used to describe the consistency or thickness/viscosity of the coating while in liquid form.

Bond: The adhesion of, or ability of, two items to stick to one another.

Bonding: The attachment between a coating film and the underling material to which it is applied.

Bounce Back: The rebound of atomized coating, especially when applied by conventional air spray methods. The air pressure used to atomize the coating bounces off the surface being sprayed keeping the material from attaching to the surface and it’s lost as overspray.

Box Coat: Spraying the first pass in one direction and the second at a right angle to the first providing more even finish distribution.

Boxing: Mixing of coatings by pouring from one container to another. When starting a large paint job, it’s wise to intermix (box) the containers of paint to ensure they are all the same color and avoid slight variations from one container to another.

Bridging: When a finish forms a layer over a crack or void rather than filling it. Often seen as white or gray pores where the finish has bridged the pore rather than fill it.

Brittleness: The lack of resistance to cracking or breaking of a coating film when bent or flexed.

Bronzing: A coloration (often green) observed on a dyed surface that contrasts with the actual color of the dye. It’s caused by a concentration of dye crystals left on the surface of the wood after the carrier evaporated. To fix the problem, wipe the surface with a rag wetted with the proper solvent or simply topcoat with a solvent-based coating.

Brushability: The ease of applying a coating by brush.

Brush marks: Ridges left after application of the coating by a brush due to poor flow, leveling or substrate wetting. Choosing the proper brush, using good technique, and thinning the coating as needed all work to reduce or eliminate brush marks.

Bubbling: A temporary or permanent film defect in which bubbles of air or solvent vapor are present in the applied film. See air entrapment.

Build: The wet or dry film thickness of a coating. See high build.

Bumps: High and low spots in a coating surface caused by unwanted flowing that occurs during curing. Caused by surface tension gradients that arise during curing.

Burn-in: Method of filling a defect in wood using a hot knife and a burn-in stick of resin or shellac. Also, the ability of a new coat of finish to partially dissolve the surface of the previous coat and attain a chemical bond creating a continuous film instead of multiple layers/coats.

Burnishing: The formation of shiny area on a finished surface as a result of rubbing.

Butyl Cellosolve: A registered, trademark name for ethylene glycol monobutyl ether. A slow evaporating, water miscible, relatively strong solvent. Commonly used as a lacquer retarder.

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Catalyst (aka, hardener)An activator or curing agent which chemically increases the rate of reaction in a coating. Not chemically consumed in the reaction (different from curing agent).

Caustic: A strong base or alkaline material.

Caustic Soda: A common name for sodium hydroxide (lye), a strong base or alkali.

Cellosolve: Proprietary name for ethylene glycol monobutyl ether. A slow evaporating, water miscible, relatively strong solvent. Commonly used as a lacquer retarder. Also know as Butyl Cellosolve.

Centipoise: One hundredth of a poise which is a unit of measurement for viscosity. Water at room temperature has a viscosity of 1.0 Centipoise.

Chalking: Formation of a powdery surface condition due to the disintegration of the surface binder or elastomer caused by weathering, fuel, or other destructive environmental factors (e.g., exposure to ultraviolet radiation). Results in a loss of gloss.

Checking: Cracks in the surface of a film finish.

Chipping: Small pieces of finish removed from the surface, typically a sign of physical damage incurred in shipping or handling. Color touch up followed by a compatible finish generally solves the problem.

Chemical resistance: A coating’s resistance to damage from solvents, acids, and alkali.

Chlorinated Hydrocarbon: A class of strong, fast evaporating, nonflammable solvents such as carbon tetrachloride, methylene chloride or trichloroethylene.

Cissing: Small holes in the surface of the film finish caused by oil, grease or silicone contamination. (aka, fisheye, cratering).

Clean and Dry: Rather than a method, the requirement for Clean and Dry describes the condition of the surface prior to finishing. The surface shall be clean, dry, and free of oil, grease, wax, and any other contaminant that may affect the adhesion of the coating. Dry means that the substrate contains less than 15% moisture.

Cleaner: A detergent, alkali, acid or similar contamination removing material, which is usually waterborne.

Coal Tar: A dark brown to black bituminous material produced by the destructive distillation of coal.

Coal Tar Epoxy: A coating in which the binder or vehicle is a combination of coal tar and epoxy resins.

Coalescence: The formation of resinous or polymeric material when water evaporates from an emulsion or a latex system, permitting contact and fusion of adjacent particles; fusing or flowing together of liquid particles.

Coat: Noun – The finish applied to a surface in a single application to form a film when dry. Verb – The act of applying a finish to a surface.

Coating: This site is focused on wood finishing so all references to coatings are generally intended to include all film forming finishes use to protect and enhance the appearance of the wood. These include, but are not limited to, clear and pigmented shellac, lacquer, varnishes, polyurethanes, and polyesters.

From Wikipedia – “A coating is a covering that is applied to the surface of an object, usually referred to as the substrate. The purpose of applying the coating may be decorative, functional, or both.”

Coating defects: Defects of wet and consequent dry coating films affecting the coating’s appearance and sometimes performance. Examples of coating defects include bubbles, craters, pinholes, orange peel, etc.

Coating System: A number of coats separately applied, in a predetermined order, at suitable intervals to allow for drying and curing, resulting in a completed job.

Cobwebbing: Premature drying of a coating during spraying causing a spider web effect.

Cohesion: The primary or secondary valence forces which bind the particles of a finish together into a continuous film.

Cold Checking: The cracking of a finish due to exposure to freezing temperatures.

Color: Aspect of the dye, stain or paint that depends upon the spectral composition of the incident light, the spectral reflectance or transmittance of the film, and the spectral response of the observer, as well as the illuminating and viewing geometry.

Colorant: Dye, pigment, or other agent used to impart a color.

Color Fast: Non-fading; resistant to fading.

Color Retention: The ability to retain its original color during weathering or chemical exposure.

Color Wheel: A circular chart of pie shaped wedges that represent the visible color spectrum. Two color wheels are used in finishing; the artist’s color wheel that presents primary and secondary colors and the finisher’s color wheel that presents common earth tones.

Combustible Liquid: Any liquid having a flash point at or above 100 degrees F (37.8C)

Compatible: The ability to mix with or adhere properly to other coatings without detriment.

Compatibility: Ability of two or more coating components to mix with each other in a wet or dry state to form a homogeneous composition without specific negative interactions.

Complimentary Colors: Two colors directly opposite one another on the artist’s color wheel.

Conical Mandrel: An instrument used to evaluate a coating’s resistance to cracking when bent over a specified radius.

Contrasting Colors: Colors separated by at least three others on the color wheel.

Conversion Coating: Also known as reactive coatings, they cure by chemical reaction. This chemical reaction may be between the oxygen in the air and the constituents of the coating, or between a catalyst or accelerator introduced into the coating material by the finisher. Drying oils such as tung and linseed, varnishes, two-part finishes, etc. are all examples of reactive coatings. The word conversion is used because a non-reversible chemical conversion has taken place in order to produce a dry, hard film. This does not mean that solvents will not dissolve or just damage the coating, just that the damage is non-reversible. See Cure.

Copolymer: Large molecules obtained by simultaneous polymerization of different monomers, as in vinyl copolymers.

Corning: The build up of powdered on sandpaper when sanding a coat of finish. May indicate the finish is not sufficiently cured for sanding. Corns on the paper surface will mar the surface being sanded and the paper should be replaced.

Coverage: Referring to the ability of a coating to cover a surface. Often referred to as spread rate calculated in either square feet per gallon or square meters per liter.

Cracking: Splitting of a coating film as a result of aging, formation of internal stresses or deformation of substrates. See the article – Cracking, Checking, Crazing, and Alligatoring

Crackle Finish: Intentional splitting of a coating film to replicate an aged look.

Craters/Cratering: Small, shallow, bowl-shaped depressions in a coating film. Viewed under magnification, these depressions frequently have drops, particles, or bands of material at their centers and raised circular edges. Some common causes of cratering are: oil particles/droplets from air lines, and substrate contamination such as silicone from furniture polish or machinery lubricants. Also known as fisheye.

Crawling: When a coating applied tends to flow away from areas leaving them uncoated. This is usually caused by grease or oil contamination of the surface to be coated.

Crazing: Formation of surface fissures (similar to checking & cracking ) that change the properties of the film. However, it is less severe than cracking and does not penetrate to the underlaying surface.

Cross Spraying: Spraying the first pass in one direction and the second at a right angle to the first, providing more even film distribution. Also known as box coating or cross hatching.

Crosslinking: The setting up of chemical links between molecular chains to form a three dimensional network of connected molecules.

Crosslinking agent: Catalytic or reactive agent which when added to resin causes crosslinking of chains (aka, curing agent, hardener).

Cure: Process by which a coating is converted from the liquid to the solid state by changes in the properties of the resin by chemical reaction (crosslinking/conversion).

Curing Agent: A hardener or activator added to a synthetic resin to develop the proper film forming properties.

Curtains: Long horizontal runs in a coating film that occur on vertical surfaces when a coating is applied too heavily. Sagging on a large scale.

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De-Gloss: The removal of the shine on a surface either by sanding or chemical de-glossers. (see scuff sanding)

Deionized Water: Water which has been purified to remove mineral salts.

Delamination: The separation between layers of coats or substrate due to poor adhesion.

Denatured alcohol: Ethyl alcohol with a small percentage of a poison added. Used as a solvent for shellac and some dyes.

Density: Mass per unit volume, usually expressed as grams per milli-liter or pounds per gallon.

Dew Point: The temperature of a surface, at a given ambient temperature and relative humidity, at which condensation of moisture will occur.

DFT: Dry film thickness. The thickness of the solids that remain on the substrate after the solvents have evaporated.

Diluent: Portion of the volatile components of a coating which is not a true solvent. Has minimal effect on the viscosity and reduces the solids content in applied coating formulations.

Dispersion: The suspension of tiny particles, usually pigments, in a liquid, usually resin.

Distilled Water: Water which has been purified by vaporizing the liquid and collecting the vapor which is then condensed back to a liquid having, in the process, removed the contaminants.

Distressing: Fly speck spotting, sand throughs, dents, scrapes, gouges, cracks, holes, and other age marks in the finished surface or on the substrate.

Drier: Chemical agent which promotes oxidation and drying of a coating. Mainly used in oil based coatings, printing inks and varnishes. Driers are usually metallic compositions and are available in both solid and liquid forms. Different groups of driers are available: primary driers (active driers), secondary driers (auxiliary driers), and combination driers.

Dry Fall: A coating which is designed to dry rapidly so that the overspray can be easily removed from the surfaces below. The coating is dry by the time it falls to the floor.

Dry Hard: The elapsed time at which a coating has reached its optimum hardness. Although finishes like shellac, lacquer, and waterborne don’t cure/crosslink, they do retain slvents in the film for long periods and continue to shrink as the solvents slowly evaporate. This slow evaporation and shrinkage is the reason behind the recommendation to wait up to a month before rubbing these finishes to a high gloss. Otherwise, the finish may continue to shrink and the pores in the wood will re-appear in the surface of the finish as dimples.

Dry Spray: Formation of a powdery surface while spraying. This is caused by too much fine overspray usually from too high a pressure at atomisation and thinners evaporating too fast between the gun nozzle and the surface. The fine aerosol formed looses its solvent and is deposited in an almost dry form on the surface.

Drying Oil: An oil having the property of hardening by oxidation to a tough film when exposed to air in the form of a thin film.

Drying time: The interval between the application of a coating and when it is ready for service.

Dry Spray: Overspray or bounce back producing a sandy finish due to the sprayed particles having partially dried before reaching the surface.

Dry Time: Time allotted for an applied coating film to reach a set stage of cure or hardness.

Dry to Handle: The degree of cure at which a film will resist deformation due to handling.

Dry to Recoat: The time required for a cured film to dry prior to the application of a second coat without adverse impact.

Dry to Tack Free: A stage at which a coating film will form a skin to which dust will not adhere.

Dry to Touch: The state of dry at which a coating film will not transfer onto an item touched lightly against it.

Dulling: A loss of gloss or sheen.

Durability: The degree to which a coating can withstand the destructive effects of the environment to which it is exposed including the ability to withstand scrubbing, abrasion, etc. Not directly related to hardness.

Dust Nibs: A surface defect in a dried coating caused by small particles settling on the surface of the finish as it was drying, before a film had formed on the surface. Repaired by sanding level and recoating or rubbing out.

Dye: A coloring material that dissolves completely in a system that is very transparent.

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Effervescence: An effect in the film caused by rapid solvent release. This “boiling” of solvent causes a pinholed or cratered appearance reducing gloss.

Eggshell: A low-luster paint sheen between flat and satin.

Elastic: The ability of a substance to return to its original shape or volume after a distorting force on the substance has been removed.

Electrostatic Spray: System of applying a coating in which the coating droplets from an air, air-assisted airless, or airless spray gun are given an electrical surface charge. These electrical charged droplets are attracted to an electrically grounded workpiece.

Emulsion: A two phase liquid system in which small droplets of one liquid are immiscible in and are dispersed uniformly throughout a second continuous liquid phase.

Enamel: Technically, an enamel is a colored varnish, or high gloss paint. Generally, the term is used for high quality, dirt-resistant paints for interior use that may have a sheen level from satin to glossy. These coatings are used for more demanding applications as in kitchens, bathrooms, etc.

Epoxy: A synthetic resin, derived from petroleum products, that can be cured by a catalyst or used to upgrade other synthetic resins to form a harder, more chemical resistant film.

Ester: Compounds formed by the reaction of alcohols and organic acids.

Evaporative Coating: Coatings that cure by solvent evaporation alone and don’t undergo a chemical conversion of the binder/resins during curing (no cross-linking). Evaporative finishes can, and usually do, undergo intermolecular mechanical changes as they cure. Lacquer and shellac are evaporative finished. Molecules in the dry film are held together by intermolecular forces that are different than the chemical bonds formed as part of a reaction, as in the case of conversion coatings. However, in many cases, binder resins present in evaporative coatings still undergo a permanent chemical conversion after most of the solvent in the coating has evaporated. See “Dry Hard.”

Exempt solvent: Solvent which is not subject to air pollution legislation. Acetone for example.

Extender: A low hiding, inexpensive pigment that fills out and extends the high-hiding pigment’s capabilities, provides bulk to the paint, and can positively or negatively have an impact on many properties. Some common extenders are clays, calcium carbonate, and silica.

External Atomization: Using air to break up a coating material after it has exited the spray gun nozzle.

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Fading: The loss of color most commonly due to exposure to sunlight (UV).

Fan Pattern: The geometry of a spray pattern.

Fast to Light: A color which is not significantly affected by exposure to sunlight.

Faux Finishing: The technique of applying finishes to a surface to make it look like another material. Faux finishes can look like leather, stone, marble, etc.

Feather Edge: Reduced film thickness at the edge of a dry film finish in order to produce a smooth, continuous appearance.

Filler: A compound used to extend or bulk a coating to provide extra body or hiding power.

Film: A coating or paint that forms a layer above the surface of the substrate.

Film Build: The dry film thickness characteristics of a coat.

Film forming process: Formation by drying of a solid and coherent polymer-matrix film from a fluid coating applied to a substrate. Drying can be physical drying (for coatings based on thermoplastic binders), chemical drying (for coatings based on reactive binders), or both.

Film Integrity: The continuity of a coating free of defects.

Film Thickness Gauge: A device for measuring wet or dry film thickness.

Fineness of Grind: The degree of dispersion of particles within a liquid.

Fingering: A broken spray pattern delivering heavier coating to one area than another.

Fire Resistant Finish: See “Intumescent Coating.”

Fish Eye: Circular voids, pock marks, craters, or separation in the coating. Fish-eyes can be caused by oily spots or silicone particles and/or by air-borne droplets that are deposited on the surface being finished. Not uncommon in refinishing when the piece was polished with a product containing silicone.

Fish Eye Eliminator: An additive (e.g., “Smoothie”) that contains silicone. Eliminates the surface tension difference on a contaminated substrate allowing the finish to flow level.

Flammable: Any substance easily ignited in the presence of a flame; any liquid having a flash point below 100F (38.8C).

Flash Point: The lowest temperature of a liquid at which sufficient vapor is provided to form an ignitable mixture when mixed with air.

Flash or Flash-Off: The point at which a sprayed coating stops flowing or leveling. Premature flash causes orange-peel when the atomized droplets do not flow into a completely flat and even film.

Flash-Off Control Solvent: An additive that extends the wet time or “flash” of a sprayed or brushed coating. See “retarder.”

Flash-Off Time: The time needed to allow the solvents to evaporate and the sprayed finish to form a surface film. The time which must be allowed after the application of a film finish before baking/forced drying in order that the initial solvents are released, which prevents bubbling.

Flash Point: The temperature at which a material will ignite when exposed to a source of ignition.

Flat: A coating that has little to no sheen.

Flexibility: The degree at which a coating is able to conform to movement or deformation of its supporting surface without cracking or flaking.

Floating/Flooding: Coating defect where a concentration of one of the ingredients of the pigment portion of a coating sits at its surface (floating) or in patches inside the coating film (flooding), leading to a color change and non-uniformity.

Flocculation: Reversible formation of clusters of particles in emulsions and suspensions. In paints, flocculation of polymer particles may occur in emulsion (latex) paints, and flocculation of pigment particles may take place in any paint because of a deficiency of emulsifier and dispersants or changes in conditions of state (pH, solvent, etc.). Flocculation may cause loss of tinting strength, hiding power, or change flow behavior.

Flood: The act of applying a coating very heavily to the substrate.

Flow: The degree to which a wet coating film can level out after application so as to eliminate brush marks and produce a smooth, uniform finish.

Fluid Tip: The orifice in a spray gun to which the needle is seated (aka, nozzle).

Fluorescent: A class of pigments which, when exposed to visible light, emit light of a different wave length producing a bright appearance.

Force Drying: The acceleration of drying by increasing the ambient temperature.

Foreign Thinner: Any thinner not recommended on the label or in published literature of the manufacturer, which can affect the coatings performance.

French Polish: A shellac base coating which is applied by manually “padding” it onto the surface.

Fungicide: A substance poisonous to fungi which retards or kills mold and mildew growth.

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Gelled: A coating which has thickened to a jelly like consistency making it unusable.

Glaze: A type of wiping stain applied over a sealed or partially sealed (washcoat) surface and then sealed in with the topcoats. Glazing stains are NOT intended for use on bare wood though thick gel stains can be used as a glazing stain. Glazes are used to highlight shapes and design elements, add a layer of color in the finish, and create faux finishes. There are some spray only, dry on contact glazes available that cannot be manipulated other than selectively removing portions of the glaze to control color intensity. These glazes are used to accentuate design features and/or create an aged/antiqued look.

Gloss: The sheen or ability to reflect light. Flat finishes have no gloss. High gloss finishes are very shiny. Also known as sheen.

Gloss Retention: The ability to retain the original sheen during weathering.

Glycol Ether: A group of relatively slow evaporating, strong solvents.

Grain: The direction, size, arrangement or appearance of the fibers in wood.

Grain Raising: The swelling and raising of wood fibers caused by absorption of water.

Grit: A measure of the size of abrasive particles used in the manufacturing of sandpaper. Grit can also be measured as the number of particles in an square inch of sandpaper surface.

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Hard dry: See “Dry Hard”

Hardener: See catalyst.

Hardness: The degree to which a material will withstand pressure without deformation or scratching. Hardness is not an indicator of durability, but harder finishes can be rubbed out more easily. Finishes can be tested for hardness using the Pencil Hardness Test.

Hiding (Hiding Power): The ability of paint or exterior stain to obscure the surface over which it has been applied. Hiding power is provided by the paint’s pigment (quality pigments cost more and work better), and is affected by how thickly the paint is applied and how well brush marks flow out.

High Build: A term referring to a coating/finish which can produce a thick film in a single coat.

Holiday: Any discontinuity, bare or thin spot when applying topcoats (you missed a spot!).

Hue: The basis of color (e.g., whether a color is red, green, etc.). Lighter or darker variations are still the same hue. Thus, a light red and a deep red are the same hue. See tint and shade.

Hybrid Coating: A coating which exhibits the properties of both an evaporative and a conversion finish. Waterborne coatings and catalyzed lacquers are two examples. Even though solvent evaporation is the primary film-forming mechanism and what creates a “dry” film, secondary conversion reactions may occur during the “curing” of the dry film – this adds toughness and chemical resistance.

Hydrocarbon: Extracts from petroleum such as gasoline, lubricating oils, solvents, etc.

Hydrophilic: A substance which absorbs or has an affinity for water.

Hydrophobic: A substance which does not absorb or exhibit an affinity for water.

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Immersion: Referring to an environment which is continuously submerged in a liquid, often water.

Impact Resistance: The ability to resist deformation or cracking due to a forceful blow.

Incompatibility: Unsuitable for use together because of undesirable chemical or physical effects. Often used in reference to coatings and/or stains which are not capable of being mixed with one another (e.g., shellac that contains wax and polyurethane or waterborne finishes).

Induction Time: The period of time between mixing of two component products and the moment they can be used. Some catalyzed finishes have a waiting period before use once the catalyst is added – read the product data sheet prior to use.

Inert Pigment: A non-reactive pigment, filler or extender.

Inhibitive Pigment: A pigment which assists in the prevention of the corrosion process.

Inorganic: The designation of compounds that do not contain carbon.

Inorganic pigment: Natural or synthetic pigment such as metallic oxide, sulfide, and other salts. Possesses outstanding heat- and light-stability, weather resistance, and migration resistance.

Inorganic Zinc: A coating based on a silicate resin and pigmented with metallic zinc which has excellent resistance to organic solvents and general weathering.

Insoluble: The inability to be dissolved.

Intercoat Adhesion: The adhesion between successive coats of finish.

Intercoat Contamination: The presence of foreign matter such as dust or dirt between successive coats of finish.

Internal Mix: A spray gun in which the fluid and air are combined before leaving the gun.

Intumescent Coating: A fire retardant coating which, when heated, produces nonflammable gasses which are trapped by the film, converting it to a foam, thereby insulating the substrate.

Iron Oxide: An oxide of iron. The natural occurring state of steel.

Isopropyl Alcohol: A volatile, flammable liquid used as a solvent commonly known as rubbing alcohol.

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Ketone: An organic compound with a carbonyl group attached to two carbon atoms. Often used as a primary solvent in thinners. Examples include acetone, MEK, MAK, and MIBK.

Kick-out: Precipitation of a dissolved binder from a solution as a result of solvent incompatibility. Can be caused by improper mixing or adding the flow control component to quickly to the mixed system.

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Lacquer: A coating comprised of a synthetic film forming material which is dissolved in organic solvents and dries by solvent evaporation. The film remains susceptible to attack by the same or similar solvents. Typical lacquers include those based on nitrocellulose, other cellulose derivatives, vinyl resins, acrylic resins, etc.. See “Evaporative Coating.”

Lacquer Thinner: A blend of solvents used to reduce the viscosity of lacquer and/or eliminate blushing (see “Retarder”).

Lap Marks: Marks left when a coat of dye, stain, or finish, including paint, extends over an adjacent coat that has been allowed to dry too long.

Latex Paint: Water-based paint made with a synthetic binder such as acrylic, vinyl-acrylic, or styrene acrylic latex. (see Polymer).

Lead-Free: Contains, by weight, less than 0.5% lead for industrial products and less than 0.6% lead in consumer products.

Leafing: Ability of flat pigments to align themselves more or less parallel with the coated surface. This property produces a reflective appearance of the film.

Level/Leveling: Leveling leads to uniformity of the surface of the coating. Leveling measures the ability of a wet coating to flow out to a smooth film after application so as to avoid leaving any surface irregularities which have been produced by the mechanical process of applying the film, such as brush marks, roller marks, craters or orange peel from spraying. Also used to describe the process of sanding the surface of a finish flat prior to rubbing out.

Leveling agent: Additive which is able to reduce the surface tension under dynamic and static conditions, to obtain an optimal wetting and leveling effect, and to improve the surface flow of the coating. Poor surface flow can induce coating defects such as orange-peel, craters, brush marks, etc..

Lifting: Softening and raising or wrinkling of a previous coat by the application of an additional coat; often caused by coatings containing strong solvents. This is usually caused by applying strong solvented coating over a curing type coating (curing type coatings include catalyzed lacquer, urethane lacquer, polyurethane and enamels.)

Lightfast: A color/colorant which is not significantly affected by exposure to sunlight.

Light Reflectance Value (LRV): The amount of light reflected from a coatinged surface. Usually reported as a percentage.

Liming: Application of a white or off-white pigmented stain over sealed wood leaving the pores colored. Colored wax is an altyernative technique that is reversible.

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Mar Resistance: The ability of a coating to resist any disturbace that alters it appearance at the surface. An important factor on items where the appearance of the finish is a top consideration (e.g., car paint). Mar resistance can be enhanced by incorporation of surface modifying additives (see surface conditioners and surface modifiers).

Metallic pigment: Pigment consisting of thin opaque aluminum flakes (made by ball milling either a disintegrated aluminum foil or a rough metal powder and then polishing to obtain a flat, brilliant surface on each particle) or copper alloy flakes (known as bronze pigments). Produces silvery and other metal-like effects.

Metamerism: A phenomenon exhibited by a pair of colors which match under one light, but not another. An example can include colors that match indoors in incandescent light and not outdoors in natural sunlight.

Methyl Ethyl Ketone (MEK): A low boiling, highly volatile flammable solvent with extremely good solubility for most vinyls, urethanes and other coatings.

Methyl Isobutyl Ketone (MIBK): A medium boiling solvent commonly used in vinyls.

Methylene Chloride (MC): A chlorinated hydrocarbon (halogenated solvent). MC is one of the oldest and most common solvents used in paint and varnish strippers. It’s very effective at removing most finishes/paints, including those that crosslink during the curing process.

Although MC is non-flammable, it is toxic and a suspected carcinogen. It metabolizes in the blood to form carbon monoxide. This causes the heart to pump harder and can trigger heart attacks in people with existing heart conditions. For this reason, if you have a heart condition, avoid using a coating remover with MC as a listed ingredient. Alkali fortified MC is often used in “marine grade” finish removers and are available at most marine supply store. Alkali fortified MC strippers are effective on tougher coatings such as epoxy and polyester. They are more expensive and hazardous to work with so additional care should be taken when selecting and using these stripping agents.

Micron: A micrometer or one millionth of a meter (.000001 meters).

Mil: One one-thousandth of an inch (.001 inches). Commonly used to denote coating thickness.

Mildew: A superficial growth of living organic matter produced by fungi in the presence of moisture; results in discoloration and decomposition of the surface.

Mildew Resistance: The ability of a finish or paint to resist mildew growth on its surface.

Mildewcide: Chemical agent that aids in the inhibition of mildew growth. Especially helpful in humid climates.

Mineral Spirits: A refined petroleum distillate having a low aromatic hydrocarbon content and low solubility; suitable for thinning of alkyd coatings. Paint thinner contains mineral spirits and often a blend of other petroleum distillates.

Minimum film forming temperature (MFFT): Temperature below which the effective coalescence of emulsion particles in a waterborne coating cannot occur. Defects, such as poor water resistance, high permeability, color and gloss variations, poor washability, etc., can result in waterborne coatings cured below the MFFT.

Miscible: Capable of mixing or blending uniformly.

Mist Coat: A thin tack coat usually applied to fill porous surfaces, seal in contamination, or seal the wood and reduce grain raise.

Moisture Resistance: The ability of a coating to resist swelling, blistering, other damage caused by moisture.

Monomer: Low molecular weight molecules capable of combining with a number of like or unlike molecules to form a polymer.

Mottled: Spots of different tones and colors next to each other resulting in a blotchy effect.

MSDS: Material Safety Data Sheet. An informational document provided the manufacturer regarding the safety and handling procedures and cautions for materials used in the workplace.

Mudcracking: A waterborn paint film defect characterized by a broken network of cracks in the film.

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Naphtha: A fast evaporating petroleum distillate solvent used to thin oil-based coatings and to clean up.

Neutral: A liquid which is neither acid nor alkali such as water; pH7.

Neutral-Tone: Color range for faux finishing that consists of off-whites, beiges, or grays that provide a base color.

Nitrocellulose: The primary resin material used in making lacquer.

Non-Drying Oil: An oil which undergoes little or no oxidation when exposed to air and therefor has no film forming properties (e.g., mineral oil).

Non-flammable: A compound which does not burn in the presence of a flame.

Non-volatile: The solid portion of a coating consisting of pigment and binder. It’s the portion of the coating left on the surface after it’s dry (solids content).

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Oil-base: Generally, finishing products (e.g., stains, clear coats, and paints) made with a drying oil, such as linseed, soya, or tung oil as the vehicle and binder, and mineral spirits/paint thinner or naphtha as the thinning agent. Also used to describe a class of stains based on fast drying alkyd binders that are reducible with mineral spirits or naphtha.

Oil Length: The ratio of oil to resin expressed as a percentage of oil by weight in the resin. Used to determine the physical properties of a resin/finish.

Opacity: The ability of a paint film to obliterate or hide the color of the surface to which it is applied. A paint with a high opacity will hide the substrate well. The opposite of transparent.

Opaque: Finishes that obscure the surface being coated. Includes a wide range of brushable and sprayable paints and some exterior stains.

Open Time: The length of time a coating remains wet enough to allow for brushing-in without lapping.

Orange Peel: Dimpled, bumpy, or wavy surface of a film similar in appearance to the skin of an orange. Usually caused by spraying in high heat, draft or a material that is too thick or heavy in viscosity resulting in poor leveling. A common defect in both spray and roll applied coatings. For some coating appliances, an orange peel effect may be desirable.

Organic: Designation of any chemical compound containing carbon.

Organic Zinc: A zinc rich coating utilizing an organic resin such as an epoxy.

Osmosis: The diffusion of liquid through a paint film or other such membrane.

Overspray: Sprayed coating that is dry when it hits the surface resulting in dusty, granular adhering particles, reducing gloss and presenting a poor appearance.

Oxidation: A chemical reaction with oxygen. The formation of an oxide; the curing mechanisms for alkyds.

Oxidative Polymerization: Mechanism of drying unsaturated binders (cooked oils, alkyds etc.) in relatively thin films in the presence of atmospheric oxygen, initiated and catalyzed by driers.

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Paint: (Verb) To apply a thin layer of a pigmented, opaque coating to a substrate by brush, roller, spray or other suitable method. (Noun) A opaque pigmented finish designed for application to a substrate, in a thin layer, which is then converted to an solid film. Paint is designed to protect and/or decorate the surface it is applied to. Generally a paint contains binders (resins), solvents, pigments, and additives. Paints may be pigmented oil-base coatings, waterborne coatings, lacquer coatings, catalyzed coatings, etc..

Pass: The motion of operating a spray gun in one direction only.

Paste: The product of a dispersion process. It is usually very high viscosity and requires dilution prior to application; a concentrated pigment dispersion used for shading.

Pattern: Shape of stream of material coming from a spray gun. Also the sequence of spraying various items to maintain a wet edge and avoid overspray.

Peeling: A film of coating lifting from the surface due to poor adhesion.

Penetrating Finish: A coating that is absorbed into the substrate rather than forming a film on its surface. Drying oils are penetrating finishes.

Percent Solids: Percentage mass of non-liquid components in coatings.

Permeability: The degree to which a membrane or coating film will allow the passage or penetration of a liquid or gas.

pH: A measure of acidity and alkalinity; pH 1-6 is acid, 7 is neutral, and pH 8-14 is alkali (base).

Phenolic Resin: Thermosetting synthetic resin produced by the condensation of phenol with an aldehyde (e.g., formaldehyde). Provides very good heat and water resistance.

Photoinitiator: Additive which, when exposed to a specific wavelength of energy, forms a reactive species which starts the chain reaction to cause polymer formation. Most commercial photo-iniators for radical curing reactions contain benzoil groups, which are mainly responsible for the absorption of energy from light.

Pickling: Application of a white, off-white, or pastel pigmented stain on bare wood leaving as little or as much color as desired. Thinned paints work very well.

Pigment: A finely ground natural or synthetic, insoluble particle adding color and opacity or corrosion inhibition to a coating film.

Pigment/Binder: A ratio of total pigment to binder solids in coatings.

Pigment Volume Concentration (PVC): The percent by volume occupied by pigment in the dried film of paint generally expressed as a percentage.

Pinholing: A film defect characterized by small, pore-like flaws in a coating which extend entirely through the film.

Plasticizer: An agent added to the resin to aid in flexibility. Compounding material used to enhance the deformability of a paint, varnish or lacquer. A plasticizer is soluble in the polymer and decreases the glass transition temperature (Tg) value, softens and adds flexibility to the product.

Polyester Resin: A group of synthetic resins which contain repeating ester groups. A special type of modified alkyd resin. Polyester finishes are among the most durable.

Polymer: Large organic molecule formed by combining many smaller molecules (monomers) in a regular pattern. Plastic-like material produced from chemical “monomers” which in turn have been produced from alcohols and petrochemicals. Polymers are used in many clear and pigmented finishes (paints), including waterborne products. The large chain of molecules adds greatly to the durability of the coating.

Polymerization: A chemical reaction in which two or more small molecules combine to form large molecules containing repeated structural units.

Polyurethane: An exceptionally hard, wear resistant coating polymer made by the reaction of polyols with a multi-functional isocyanate. Provides toughness, flexibility, weather resistance, chemical resistance, and abrasion resistance to the coating film. Commonly used to make topcoats.

Polyvinyl Chloride (PVC): A hard tough plastic solid used for plastics and coatings, commonly known as vinyl.

Porosity: The presence of numerous minute voids in a cured material.

Post-cure reaction: Crosslinking reaction which occurs in cured coating due to the presence of an excess of a hardener. Can cause coating defects such as internal stress, decreasing adhesion, durability, and flexibility.

Pot Life: The length of time a coating material is useful after its original package is opened or a catalyst or other curing agent is added. As mixed material reacts in the pot, the viscosity always increases.

Potable Water: Water fit for human consumption; as in drinking water.

Powder coating: 100% solid coating generally applied by an electrostatic process as a fine, dry powder to the surface and then heated above its melting point so the powder particles flow together or cure.

Practical Coverage: The spreading rate of a coating calculated at the recommended dry film thickness and assuming 15% material loss.

Precipitate: An insoluble substance separated from solution by the action of some reagent added to the solution, or of some force, such as heat or cold. The precipitate may fall to the bottom, may be diffused through the solution, or may float at or near the surface.

Primary Colors: Colors that cannot be produced by mixing any two other colors. They are red, yellow, and blue.

Primer: The first complete coat of paint applied in a painting system. Many primers are designed to provide adequate adhesion between the surface and subsequent topcoats. Most primers contain some pigment, some lend uniformity to the topcoat, some inhibit corrosion or the substrate, and some stop the discoloration of the topcoat.

Primer-Sealer: A priming system that minimizes or prevents the penetration of the topcoat into the substrate.

Print Resistance: The ability of a coating to avoid pressed-in markings from an object placed on it.

Promoter: See Accelerator

P.V.A. (Polyvinyl Acetate): A binder most widely used in economical interior latex wall paints.

Pyrometer: An instrument used to measure the temperature of a surface.

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QUV: An accelerated testing device designed to evaluate the fading properties of a coating by exposure to high intensity, ultraviolet light.

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Re-coat Time: Interval required between the application of successive coats of finish. This time period is usually listed on the label. The actual time may vary from the manufacturer’s guideline in cases where the temperature is well above or below 70 degrees and the humidity is higher than 50%.

Reduce: To add solvent in order to thin a material to a workable thickness (viscosity).

Reducer: Commonly known as thinner.

Reflectance: The ratio of the light that radiates onto a surface to the amount that is reflected back.

Related Colors: Two colors that are next to each other on the color wheel.

Relative Humidity: The ratio, expressed as a percent, of the quantity of water vapor actually present in the air to the greatest amount possible at a given temperature.

Resin: Solid, semi-solid or pseudo-solid organic material which has an indefinite and often high molecular weight. Exhibits a tendency to flow when subject to stress. Can be natural or synthetic. Used as the binder and/or film forming agent in finishing products.

Retarder: Solvent added to a coating to slow down its evaporation rate.

Rheology: The science characterizing fluid deformation or flow.

Roller: A cylinder covered with lamb’s wood, felt, foamed plastics or other materials used for applying paint.

Runs: Sagging and curtaining of a coating or paint film, usually caused by improper thinning, excessive film build or poor application techniques.

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Sag/Sagging: Narrow (or wide curtain-like) downward movement of a film finish; caused by the application of too much coating, the collection of excess quantities of finish at irregularities in the surface (cracks, holes, etc.), or excessive material continuing to flow after the surrounding surface has set.

Sag Resistance: The ability of a coating to be applied at proper film thicknesses without sagging.

Salt Atmosphere: A moist, heavily ladened air with a high chloride concentration; used as a test for accelerated corrosion evaluations and also present near sea coast areas.

Salt Fog Test: A cabinet designed to accelerate the corrosion process in evaluating coatings; combines 100% humidity with a 5% salt concentration at 100F in an enclosed cabinet.

Sandability: Ease of sanding of a coating.

Sanding Sealer: Especially hard first coat that can seal and fill, but will not obscure, the grain of the wood. Formulated to give better filling and sandability than the topcoat products. The surface is then sanded before subsequent coats are applied.

Satin Finish: Sheen of coating with a 60 degree gloss reading between 10 and 40.

Saponification: The alkaline hydrolysis of fats whereby a soap is formed; typical reaction between alkyds and galvanized metals resulting in peeling.

Scratch resistance: Ability of a coating surface to resist to damage caused by sharp and hard objects. Influenced by the hardness, the coefficient of friction and the thickness of the film.

Scrub resistance: Ability of a coating surface to resist to damage caused by rough objects in the presence of an active medium (water or organic liquid, abrasive material).

Scrubbability: The ability of a coating to resist wearing away or changing its original appearance when rubbed with a brush, sponge, or cloth and an abrasive soap.

Scuff Sand: To lightly sand in order to remove the shine or roughness of a surface prior to recoating.

Secondary Colors: Colors formed by mixing together two primary colors. They are orange, green, and purple.

Sealer: A coating used on absorbent surfaces prior to topcoats.

Seeding: Formation of small agglomerates or gel particles (seeds) in a coating. Caused by resin insolubility, aggregation of pigment particles, or a combination of both factors.

Semi-gloss: A finish with a sheen level between high gloss and satin (or eggshell).

Settling: The sinking of pigments, extenders, flatteners or other solid matter in a coating/paint, on standing in a container, with a consequent accumulation on the bottom of the can.

Shade: A shade is created when black is added to a color. It is a darker variant of a color.

Shading/Shading Stain: A shading stain is a dye and/or pigmented colorant added to a thinned clear film forming finish used to add coloring in specific areas on a piece being finish. Shading can be used to accentuate a design feature, increase the color intensity, alter the existing color, or to blend and uniform area(s) on the piece.

Shelf Life: Period of time during which a finishing product stored according to the manufacturer’s instructions (packaging, temperature, humidity) retains its expected properties.

Shellac: Alcohol-soluble resin derived from lac available in a variety of grades/colors. Lac is a substance secreted by insects on tree branches, mainly in India. Used as a sealer for sealing knots, a clear finish, and in “alcohol-based” primers. The thinner is denatured alcohol.

Siccative: Catalyst used for drying according to the oxidative polymerization mechanism (aka, drier).

Silicone Resins: Resins based on silicone instead of carbon, generally used for their outstanding heat resistance and water repellency.

Silking: Fine parallel irregularities in a paint film that give the appearance of silk. This defect usually is a special case of floating and flocculation in coating finishes.

Skinning: The formation of a solid membrane on the top of a liquid, caused by partial curing or drying of the coating during storage.

Slip agent: Additive which reduces the friction coefficient and thereby improve slip characteristics of coating films. Various waxes, silicones or modified polyesters can be used to increase surface slip.

Softwood: The group of trees (fir, pine, spruce, hemlock) characterized by its needles and being (for the most part) evergreen. The term does not refer to the hardness of the wood, only its classification.

Solids Content: Non-volatile matter in the composition of a coating. The ingredients in a coating that, after drying, constitute the dry film. Solids are composed mostly of binder and pigment (in paints).

Solids by volume: Percentage of the total volume occupied by nonvolatile compounds.

Solids by weight: Percentage of the total weight occupied by nonvolatile compounds.

Soluble: The ability of a material to be dissolved in a liquid. For example, sugar is soluble in water.

Solvent: A solvent is a liquid that dissolves another substance to form a solution (a homogeneous mixture). The material dissolved in the solvent is called the solute. Together, the solvent and solute comprise the solution. The solvent is the component in the solution that is present in the largest amount or is the one that determines the state of matter (i.e. solid, liquid, gas) of the solution. Solvents are usually, but not always, liquids. They can also be gases or solids. Solvents can dissolve solids, liquids or gases. Water is a solvent. Every day, people dissolve soap in water creating a soap solution. Different classes of solvents dissolve different substances more readily. For example, some oils readily dissolve in mineral spirits, but not in water.

Solvent Entrapment: The encapsulation of solvent within a cured coating film due to improper drying conditions; results in a non-continuous film.

Spar Varnish: Exterior varnish with good water resistance and the capability to resist weathering. Named for its original use on the spars of ships.

Specification: A set of instructions detailing the plan for coating of a project; a list of criteria for a coating.

Splotch: See “Blotch.”

Spray Head: The combination of needle, tip and air cap.

Spray Pattern: The configuration of coating sprayed on the surface.

Spread Rate: Coverage, usually at the specified dry film thickness.


Stain Bleed-through: When tannin found in certain types of wood (such as oak, cedar, or redwood) migrates through the coating, causing discoloration. Also, discoloration from a contaminant on the substrate.

Stain Resistance: The ability of a coating to resist soiling.

Stripping: Removing old paint, varnish, etc., by using a chemical paint remover, sandpaper, heat gun, or scraping tools.

Strong Solvent: Any solvent capable of dissolving large quantities of a specified subject.

Substrate: Any surface to which a coating or sealant is applied.

Surface Conditioner: Molecular, or more frequently, micro-phase surface modifying coatings additives such as fine particle size waxes designed for use in coatings to impart improved mechanical, optical, and electrical surface properties to organic coatings. They enhance their anti-blocking properties, scratch and mar resistance, and impart water-repellency. Surface conditioners are widely used in wood coatings to improve the blocking resistance and sandability, scratch and abrasion resistance, matting and soft surface feel.

Surface Defects: Defects that occur during and immediately after application of a finish and which have a negative influence on both the coating appearance and performance. Surface defects may result from a number of causes, including poor substrate wetting, insufficient flow, surface distortion associated with solvent evaporation and surface cooling, foaming and air entrapment, and contamination of the finish, air or substrate.

Surface Modifiers: Collective term for several groups of additives to enhance properties of ready coatings (slip control, anti-blocking, abrasion and scratch resistance etc.), same as surface conditioners.

Surface Preparation: Any means for preparing a surface for finishing including cleaning, grain-raising, sanding, filling, and spot priming.

Surfacer: Pigmented composition for filling depressions in order to obtain a smooth, uniform surface before applying the finish coat.

Surfactant: Contracted from surface-active agents, these are additives which reduce surface tension and thereby improve wetting (wetting agents), help disperse pigments, inhibit foam, or emulsify. Conventionally, they are classified as to their charge: anionic (negative); cationic (positive); nonionic (no charge); or amphoteric (both positive and negative).

Surfactant Leaching: Also called water-spotting and weeping. It is often a tan-colored, glossy residue that can form on the surface when exterior latex paint is applied under conditions that are cool and damp, that result in slow dry of the paint. May not readily wash off, but generally will weather off within a month’s time.

Suspension: A relatively coarse, non-colloidal dispersion of solid particles in a liquid.

Synthetic: Manufactured, as opposed to naturally occurring.

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Tabor Abraser: An instrument used to measure abrasion resistance.

Tack Cloth: A fabric impregnated with a tacky substance that is used to remove dust from a surface after sanding or rubbing down, and prior to further topcoats. It should be stored in an airtight container to preserve its tackiness.

Tack free: Completion of the initial cure process of a coating. Airborne dust and soil will no longer be trapped in the coating.

Tacky: The stage in the finish’s drying process at which the film is in sticky when lightly touched.

Tails: Finger-like spray pattern produced by improper gun or coating material adjustment.

Tape Time: The drying time of a coating required prior to masking sections for lettering or striping after which tape will not distort the finish.

Telegraphing: Revealing of the substrate surface profile through the coating after cure. Commonly caused by not using a filler or primer.

Thermoplastic: Resin that will repeatedly soften when heated and harden when cooled. Typical of the thermoplastics family are the styrene polymers and copolymers, acrylics, cellulosics, vinyls, etc..

Thermoset: Resin that will undergo or has undergone a chemical reaction by the action of heat, catalysts, ultra-violet light, etc., leading to a relatively infusible state. Typical of the plastics in the thermosetting family are the aminos, polyesters, alkyds, epoxies (not all), and phenolics.

Thinner: A liquid that, along with the binder, forms the finish’s vehicle. The thinner evaporates after the finish is applied. The liquid used to thin the coating.

Thixotropic: A full bodied/thick material which undergoes a reduction in viscosity when shaken, stirred or otherwise mechanically disturbed but which readily recovers its original full bodied condition upon standing (e.g., a good gel stain).

Titanium Dioxide, Rutile (TiO2): A high opacity, bright white pigment of the non-chalking type, used as a prime pigment in quality paints. Prepared from the mineral ilmenite, or rutile ore.

Toluene/Tylol: An aromatic solvent with a high boiling range and low flash point classified as a strong solvent.

Toner/Toning: A coat of finish that has dye or pigments mixed in that is sandwiched betwen clear coats.

Tooth: In a dry film, a fine texture imparted either by a proportion of relatively coarse or abrasive pigment, or by the abrasives used in sanding; this texture improves the burnish properties and also provides a good base for the adhesion of a subsequent coat of the finish.

Topcoats: The clear protective coats of finish applied to a surface.

Touch up: To repair misses, mars, scratches and places where the coating has deteriorated or been damaged, in order to restore the finish.

Transparent: Clear enough to see through.

Translucent: Allows light to pass through but not clear enough to see through.

Trisodium Phosphate (TSP): A cleaning compound based on an alkaline material. Because it contains phosphate, its use is controlled in certain geographical areas.

Two-Pack (2K): A coating which is supplied in two parts and must be mixed in the correct portions before use in order to cure.

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Undercoat: The coat applied to the surface after preparation and before the application of a finish coat (usually used in metal finishing).

Ultraviolet Radiation (UV): The portion of the radiant energy of the sun’s spectrum that causes damage to coatings and sealants and to the surface of unprotected wood.

UV-absorber: Compounding material which, through its ability to absorb ultraviolet radiation and render it harmless, retards the deterioration caused by sunlight and other UV light sources. Incorporated into a coating, this additive screens the most harmful UV portion of light and thereby protects films and sensitive substrates from the photo-destruction.

UV/EB cured coating: Coating in which the liquid application changes under UV/Electron Beam exposure within seconds into the completely cured film.

UV-curing: Process using UV light or Electron beam exposure to cure coating films. It converts the incoming radiation energy into a chemical reaction of non-saturated oligomers and/or monomers, in which the photoinitiator plays a key role.

UV/Light stabilizer: Chemical added to a coating to absorb the ultraviolet radiation present in sunlight and stabilize organic materials.

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Vapor Barrier: A moisture-impervious layer which prevents the passage of water into a material or structure.

Vapor Transmission Rate: The rate at which moisture passes through a material or coating.

Vehicle: The liquid portion of a coating in which the pigment is dispersed. Comprised of binder and thinner.

Vinyl: A clear synthetic resin used in some finishes.

Vinyl Copolymer: A resin produced by copolymerizing vinyl acetate and vinyl chloride.

Viscometer: One of several types of instruments for measuring a liquid’s viscosity.

Viscosity: The thickness of a coating material in its liquid form. Measurement of a fluid’s resistance to flow. The common metric unit of absolute viscosity is the poise, which is defined as the force in dynes required to move a surface one square centimeter in area past a parallel surface at a speed of one centimeter per second, with the surfaces separated by a fluid film one centimeter thick. Since viscosity varies in inversely with temperature, its value is meaningless until the temperature at which it is determined is reported.

Viscosity Cup: An efflux viscometer using a measured volume of liquid flowing through a precise orifice (see <a href=”finishing.tips” target=”_new”>Measuring Viscosity</a>).

Voids: Holidays or holes in a coating.

Volatile Content: The percentage of materials which evaporate from a coating. The solvent portion of a coating.

Volatile Organic Compounds (VOC): Any carbon compound that evaporates under standard test conditions. Essentially, all solvents except water are classified as VOCs. Some government agencies are limiting the amount of volatile organic compounds permitted in finishes because of concerns about environmental and health effects.

Volume Solids: The volume of the solid components (pigment plus binder) of a finish, divided by its total volume, expressed as a percentage. High volume solids provide a thicker dry film.

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Washcoat: A coat of highly thinned finish used to partially seal the wood’s surface before a dye, stain, glaze, or toner is applied. The washcoat provides a base for more uniform coloring.

Wash Primer: A thin paint designed to promote adhesion or to be used as a barrier coat.

Waterborne: Finish made with acrylic, vinyl or other latex resin types, and thinned with water. It dries more quickly than oil-based finishes, has relatively low odor, may have some water vapor permeability, and cleans up easily. The liquid component is predominantly water. Often referred to as water-base.

Water-reducible: Ability to be diluted with water or a water/co-solvent mixture.

Water Spotting: A surface defect caused by water droplets depositing a circular ring of contaminants.

Water White: A term used to describe the color of a coating in its liquid form. As clear and colorless as drinking water.

Weatherometer: A machine designed for the accelerated testing of coatings.

Wet Edge: The edge or end of a wet, coated area that is still workable and will blend easily.

Wet Film Thickness: Thickness of a liquid film immediately after application, before it begins to dry.

Wetting: The ability of a vehicle to flow onto the surface in order to achieve a good bond.

Wiping Stain: A stain applied to bare wood and the excess is wiped off before it dries.

Wood Grain: The arrangement of layers of wood fiber growth.

Wrap around: Phenomenon by which electrically charged finish droplets curve around the rear side of the object being sprayed.

Wrinkling: Skinning over of the film surface and absorption of the liquid within the film.

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Xylene/Xylol: A flammable aromatic hydrocarbon solvent used in epoxies and fast drying alkyds.

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Zinc Chromate: Bright yellow pigment that chemically is substantially zinc chromate, although its precise composition is rather complex. Its chief use is in anti-corrosive paints and primers for steel.

Zinc Oxide: A fine particle, white pigment used in paint for mildew resistance and film reinforcing properties.

Zinc Stearate: A metallic salt of fatty acid possessing a surfactant-like combination of hydrophilic and lipophilic molecular characteristics. Zinc stearate can perform the following functions in formulations; lubricants, coupling agents, waterproofing agents, viscosity modifiers and flatting agents. Zinc stearates are used in the production of color concentrates, phenolic resins and compounds, coatings, paints, varnishes, and sanding sealers.