Aluminum Plate Lithography
Aluminium is the metal of choice amongst North American printmakers and commercial offset printers. For waterless lithography, this turns out to be a very lucky decision because of the strong bond between aluminium and silicon molecules. While most art printmakers who use metal, are using ball grained plates because of the necessary texture for drawing and for the amount of water they can hold in traditional gum-etch processes, the grain is not as important for waterless techniques. In fact, much better fine detail is possible from smoother plates, as has been discovered by commercial offset printers. For years I have been using quite smooth commercial plates for my waterless process, doing toner washes and flats with Sumi ink, because of the superior quality of the image - not to mention the saving in plate costs. Because of the many plates I use in the multicolor editions I print, I have been looking for some way to reuse plates, in the hope to save money. I had found that all plates could be stripped of the silicone coating and reused, but the need to use a stronger silicone stripper, made this technique less desirable. I looked for a way also to reuse the many ball grain plates I had on hand, trying sandblasting and graining with levigators or a woodworkers palm sander. None of these seemed the best approach because of various problems that arose. Finally, after much experimentation and many attempts, I have found a simple and effective method. I have included a simple explanation of the technique in the previously updated paper on my waterless process.
Problems to overcome
Because I have found that the smoother the plate, the better the image in most cases, I looked at the back of plates as a source of metal. This would also overcome the deeper grain that had to be eliminated by working down the surface. When one tries to work with the backside, one soon finds that water is rejected because of dirt, oxides and other things that accumulate on used plates. Trying to rid these with counter etches did little good, and regaining with silicone carbide was very slow, as well as more damaging to the thin plate. Using gentler kitchen abrasives alone, similar to the technique of preparing intaglio plates, was not successful, because of the larger size of litho plates and the contaminates. The main problem was to find a method of removing the debris so that water would take to the surface.