Silverpoint

Silverpoint is a technique that uses a fine piece of silver (like the lead in a pencil) to draw on specially prepared paper.  The silver by itself will not leave a mark on the paper, but for this technique, the paper is specially coated with 'carta tinta', a mixture of bone ash, Arabic gun and Chinese white.  To this mixture, the artist can add color of his choice.  The mixture is then boiled.  After it has cooled it is applied over white paper. 

In Roman times it was used as a means for writing on 'pergamino' which was made from lamb skin.  The great time for silverpoint was during the Italian renaissance.  Leonardo da Vinci was one of the most outstanding practitioners.