Glass Paints – Which Works Best?Paul S
Most paints simply won’t adhere well to glass and will eventually flake and peel. To successfully paint glass we either need a primer or a paint that’s specifically made to bond to it.
To achieve good adhesion on glossy surfaces we often use a primer that’s designed to hold fast and then apply the paint over it. However, when back painting glass, the primer has to be clear (transparent) which limits our choices. There are clear bonding primers on the market, but most are made to work with plastics or metals. A couple exceptions include Bulldog adhesion promoter and CIC Mustang adhesion promoter.
Bulldog is advertised for use on metals, plastics, and glass, but it didn’t perform well when I tested it several years ago. It may be improved at this point and worth trying (be sure to do an adhesion test) – it’s available in aerosol cans. I haven’t tried the Mustang adhesion promoter, so I don’t have first hand experience, though I’ve heard it does a good job. Mustang is recommended for use with all solvent-based urethane, epoxy, acrylic, lacquers, primers, sealers and base coats which offers a lot of options for the painter/finisher.
Glass Paint That Works
Some paints are specifically formulated to work with glass. Two well known brands are Glassprimer Glass Paint and Matthews 1-Shot enamel. Though I use and highly recommend Matthews Acrylic Paint and related products for wood and metal, I use Glassprimer for glass work. I first discovered it when I needed a custom color for glass that had to have exceptional adhesion, cohesion, and solvent resistance. I needed to back paint the glass to match the designers color theme and then glue steel hinge plates directly to the paint. The paint hides the hinges that operate the large glass doors on the display cases we were building for the Smithsonian Museum (see picture below). Needless to say I had to do some serious testing and it passed really well. For the work I do, the performance of the paint and option to order it in any color justifies the high cost.
Whatever you choose, be sure to perform a cross hatch adhesion test after letting the finish cure for a few days. It’s surprising how often coatings fail this test even if they are marketed as highly capable. I’ve tested various consumer grade bonding primers as well as professional lacquers, vinyl sealer, and catalyzed acrylic polyurethane (2K PU) on glass and they didn’t work.