Before I posted, I did a search in the archives for "vinegar". Returned several hits. Here is a link to a web article where the etching process does indeed use household vinegar (with drugstore-strength hydrogen peroxide and table salt.) http://quinndunki.com/blondihacks/?p=351
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Vinegar, H2O2 and NaCl etch solution
2011-08-19 by kx4om