I think they are made out of silver nitrate G.
The only time I have come across them was in a medical use and that was for burning scar tissue. The old doctor that was applying it to me was giving me the history of it. And the indelible pencil was mentioned
I think you can get them in art shops but not quite the strength of the caustic sticks used by the medics. He also mentioned another type that gave you a purple dye when wet which you could get a copy off using tissue paper. He had used them when studying medicine so he could copy his notes at a later date.
Did they not used to etch some metals with them as well?
Last edited by mad_jock; 14th Jul 2013 at 06:05.