Hi Anne,
Just thought I would add that another term commonly used for that type of work, as opposed to acid reduction, is ACB or "Acid Cut Back". Acid Cutting is a method that has been widely used by many quality manufacturers. It involves taking the piece of glass and protecting the surface area one wants preserved with materials that are acid resistant. The application of acid then cuts, or reduces the surface that is exposed, resulting in a relief pattern. Companies such as Webb, Daum, Galle, Schneider, Lalique, Steuben and more used the method. It is actually a little more common, IMO, to see the technique used on layered glass, allowing for different colors to be exposed, as opposed to etching monochrome glass. It seems to me the French used ACB techniques on monochrome glass more than most other countries.
Craig