A technical dictionary of printmaking, André Béguin.


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Bordeaux-etching
This process is mainly used for "etching" on zinc. For other metals it is rather difficult to use. The actual "etching" is done in a bath filled with a copper-sulphate solution. The copper-sulphate is dissolved in water. For a rather "strong" bath use 50 grams of copper-sulphate on a liter of water. For lighter etchings however 25 grams on a liter is reccomanded, or even less if you deal with fine aquatints. copper-sulphate can be bought in powder (cristals) and is harmless when it is not in contact with water. When it is mixed with water it is "activated" and can cause irratations on the skin and even burns. So be careful.
The process is non-toxic and easy to manage. There is no real etching involved as in the traditional techniques. The copper in the copper sulphate solution exchanges place with the zinc. This zinc will dissolve in the liquid as well as the copper compound. This copper compound however tends to remain in the etched lines, and will stop eventually the process. To avoid this occuring it is necessary to keep the liquid in motion. This can be done by slowly stirring. One can also use this process for deep relief etching.
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