Practically any type of aluminium sheeting can be used for waterless lithography, but I presume most will be using those commonly used by printmakers coming in .012 inch thickness and grained on one side. After using the grained side, the plate can be recycled by cleaning the back and preparing it for taking on an image. If these plates are not readily available for you, then the aluminium used for roof flashing can be cut into the size you need and prepared as well. Most roofing metal will come in a roll so the curve has to be removed, but more on that later if it becomes an issue.
Aluminium oxidizes very quickly and it should be removed and replaced with aluminium silicate for use in both direct drawing or as photo plates. There are two compounds that work well and should be available in your community. The one I use and recommend is sodium metasilicate that comes as a powder that replaces TSP (Trisodium phosphate), which promotes growth of algae and not used as a cleaning agent any longer. Some of these cleaning powders are not pure metasilicate, but contain sodium carbonate or other alkaline chemicals. About a good heaping tablespoon in a liter or quart of water is all it takes. This solution doesn’t harden and remains water soluble.
The other chemical is sodium silicate also known as waterglass. This comes as a heavy viscous solution used by potters and should be available from their suppliers. Unlike metasilicate, waterglass hardens on drying and becomes waterproof. When used to establish the aluminium silicate layer, it must be flushed off after it had time to react for a few minutes. It will depend on the viscosity of the product you have; the one I use from the potters supplier is diluted by 10X with water. While most household cleaning compounds contain some form of sodium metasilicate, they will likely have other chemicals that may be detrimental to our intended use of the alkaline solution.
The reason I have found it best to form an aluminium silicate layer is that silicone seems to bond better to the metal, and when it comes time to recycle the plate, the weak acid solution used also attacks this layer faster. Chemically the affinity of aluminium and silicone elements to each other is very positive for this process. These two elements are the formation of much of rock in the universe, with silicone being the second most common element we have.
After any ink is removed from the back of the plate, the surface is scrubbed with a sharp grit powder or one of the green 3M pads made of Nylon into which silicone carbide grit is bonded. A pad with scrap carpet glued to one side makes a good surface to hold the pad and they can be used just with the grit or for their own gentler character on our plates.
The first resurfacing is harder than recycling, but work on the metal until it will hold water all over - just like when preparing an etching plate. Fine scratches work very well for use with various drawing pencils and toner chalks, so don’t try to get a mirror smooth surface. In your graining sink, make sure that the slats or other a perfectly flat plane area is used when working on these thin plates, otherwise the wide uneven slats will form a pattern on the metal. I use scrap plastic grills once used for diffusing fluorescent lights, held up on accurate level wooden slats.
After the surface is prepared, it is flushed with water and quickly squeegeed off and dried. Unlike traditional lithography, grain is not necessary to hold water, so a rough textured surface is in fact detrimental for a good waterless surface. I place two prepared surfaces together as they are cleaner than the other side of old plates. With care from bending the fragile metal, the plates can be recycled many many times as very little metal is removed in each operation.
As a beginner in waterless, I strongly recommend that you do not start with large plates as all the information you can get for any technique can be gotten from a plate about 9 x 12 inches - and wastes less material. This thickness of metal can be cut with a draw knife or even a common Olfa box cutter and a straight edge. Just score the metal deep enough to be able to bend it evenly along the cut the first time, then bend it back and forth until the pieces separate.
Next post I will talk about drawing materials.
Copyrighted Nik Semenoff 2008