I recently started to work on a silverpoint drawing. Or rather, a metalpoint drawing. I experimented with gold point as well as silverpoint, and experimented with using an old gold ring and the back of a sterling spoon to shade large areas. Gold will not tarnish but silver will, in time, and I must confess that I lost track of which I did! I also goofed and grabbed a graphite pencil and did some shading before I realized my mistake.

The drawing is on a marble dust/white gouache gesso base on vellum.
Being able to smudge with a stomp was a nice surprise, but I did not attempt to erase (although I understand Golden Silverpoint Ground allows you to do a little of this).

I wanted to go over some of my mistakes with gouache — but first I wanted to see what the drawing looked like tarnished first (silverpoint ages to a soft sepia tone), and I did not want to wait months/years to see.

Apparently the silver reacts with H2S in the air (hydrogen sulfide which is a rotten egg smell) to tarnish, and it depends where you live in the world. i am in Canada, in winter, and leaving the drawing outside in the air was not one of my options!

I found some collectors who were aging silver rings prematurely by hard-boiling some eggs, mashing them in a ziploc bag and throwing the rings in. The H2S is produced by the eggs. The results in just 15 minutes were quite impressive!
So I decided to replicate the experiment with a plastic box, 3 over-cooked hardboiled eggs, masking tape, some props to rest my drawing on (you don’t need these in the end), and my drawing.

Workflow:
1. Find a plastic box with lid large enough for your drawing.
2. Over-cook enough hard-boiled eggs so than when mashed will cover the bottom of the box.
3. Tape the drawing with masking tape to the lid with the drawing facing the fumes, and with enough clearance so that the egg doesn’t touch your drawing.
4. Put the lid on and time the aging. I checked every 15 minutes. I found that after 120 minutes the aging had stabilized.

Results:
I obviously found that the areas where I had drawn in silver stayed a dull grey, but some areas of the silverpoint were a nice sepia tone.
The following photos show my setup, and pre and post photos of my silverpoint.