For some reason my efforts have been completely overlooked by most etchers and they either dona€?t use my discoveries or refer to others who have renamed my original research. I did not realize that Goya might have used Basic Copper Sulphate(WSDTY) alone to etch his zinc plates. Fabiola has been doing wonderful research into what materials were used by early etchers for their plates, revealing many common chemicals were being used by some etchers instead of nitric acid, which might have been hard to get. While these household materials would etch most metals somewhat slower than my process, they certainly would be safe to use on the common plate metals. She holds workshops on safer etching and use of a burin as well in many Italian cities a€“ which I wholly support.
You will find how to remove all toxic materials if you decide to no longer etch plates. I explain how to remove the copper, aluminium and zinc compounds by precipitating the metals and then filtering them out. The liquid can be put down the drain as metals have all been removed. In my original articles, I had stated that bisulfate was not needed if zinc was the metal being used, but I have found that the bath cannot be regenerated as bisulfate is required for all metals to keep in acidic in nature.
I must also add that table salt is not the best salt to use because it contains calcium silicate to keep it from clumping in damp weather. This forms calcium sulfate, which is insoluble Plaster of Paris used for making molds etc. The sodium bisulfate is best bought from a shop that caters to swimming pools and hot tubs. It is a mild sulfurous acid (H2SO3) used in many other crafts where a less dangerous acid is required. I chose it because salt and the bisulfate are both dry chemicals and only need to be mixed in water as needed; keeping dangerous liquid acid off the studio shelves. To precipitate zinc, one should use sodium metasilicate or plain liquid sodium silicate, also known as Waterglass. It is available from pottery suppliers, but you must know that it dries to be waterproof if spilled. The metasilicate comes as a powder and is always dissolves it water, so the best to use. I used to get it as s TSP substitute, but it no longer seems to be available in the large hardware chain in North America.
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