How long does it take for the drawing to achieve the patina, or color change?
First, opinions vary on what’s occuring to cause the change. Some authoritive sources call it “oxidation;” others state that it is more an effect of atmospheric sulfur. I know that works framed behind glass can take years to begin to change. I also know that several works I stored in a basement for three months changed considerably during that brief time. There was a noticeable aroma of sewer gas, so perhaps there’s a connection – and, I must add, it was pretty humid, so atmospheric water vapor might also be a contributing factor. I haven’t been able to duplicate the conditions in my studio, but if I do I’ll post it here. I’m afraid the answer is, “It depends.” I tend to go with the sulfur theory, so if you live, say, downwind of a pulp mill with a bad stack scrubber, maybe your drawing will acquire the patina in as little as a day. Also, depth of the silver deposited on the surface makes a difference; light shading and blends will change rapidly, giving a most unusual quality to the d
