Printing on Aluminum plates
I have made some prints on Al and am turning to the experts on this list for a problem I need to resolve.
The prints are impressionistic, and noticeably different from those on paper. They are sufficiently interesting to warrant refinement.
The ground is an acrylic gesso diluted with water to the desired thickness. To 250 ml of it are added 2 heaping spoons of flour sand (that has been sieved through nylon hose). This mix is once again sieved through the same material before applying to thoroughly cleaned Al plates with a roller. Each application is dried with a hair dryer on hot setting, turned 90 degrees and recoated. This is repeated 2-3 times till a desired opacity is obtained. Grounded plates are dried for 24 hours before application of formalin-hardened gelatin on 3 successive days.
Prepared plates are dampened with a wet towel before application of the gum emulsion. The sensitizer stock solution is 10% Am. Di.
The problem: upon application of the emulsion with a dampened foam brush, the surface sometimes develops holes in the gelatin layer. Notwithstanding, I continue printing 2-3 gum passes, sometimes run a cyano pass and everything seems ok. When I dry the developed print (hot hair dryer), I find pock marks that are either colored or white, suggesting that the flour sand has balled up. In some prints, this actually enhances the interest in the print. In others, it looks like a flaw that should be avoided.
The people who supplied me with the sand flour suggest that I use water glass (sodium silicate) or gum arabic instead of water in preparing the gesso ground before adding the sand flour to it.
Your suggestions would be greatly appreciated.