I have recently begun using your Transparent Shading Gray from the GOLDEN Airbrush Color series. I am having trouble with the permanency of the bonding to the gesso surface and/or other airbrushed colors. I find very delicate spray layers can be wiped off even after the layer is "supposedly" dry and cured (24 hours later). Are there any problems with periodically applying a spray coat of Airbrush Transparent Extender over the entire painting, or selected areas, to seal these delicate paint applications?
One of the properties of the Opaque and Transparent Airbrush Colors is their use for specialty tricks for commercial illustration. Until all of the retarder has left the film, and it has been cured and not just dried to the touch, it's very likely the Shading Gray (and other colors) can lift easily with water or an alkaline solution. Another issue is light misting of color doesn't develop a strong continuous film. You've hit the nail on the head with using the Airbrush Transparent Extender to seal off after the paint has been applied. Please read "Beginning Airbrush Tips II" at: http://www.goldenpaints.com.