Metal points were a popular drawing material in the Renaissance period prior to the discovery of graphite. Lead point was the easiest of metals for the artist or draughtsmen to use as, unlike other metals, lead required no ground preparation of the paper.
The lead was shaped and placed into a stylus and used by the draughtsman as an under drawing tool prior to ink application and the creation of ruling lines. Lead is greyish blue and was used to produce dark grey, bold lines of varying thicknesses.
There are a few problems associated with lead, both for the draughtsman and the conservator. It is a very soft metal and therefore blunts very easily. This means that it had to be re-shaped constantly. It was often alloyed with tin to reduce this problem. The indentations it caused to the surface of the paper could cause unwanted ink blots.
Lead becomes darker when it has been in contact with air, and this can lead to difficulties in material identification. The use of faint lines of lead in under drawing often means that it may be confused with graphite. Lead can chemically change to lead carbonate and this leads to virtual invisibility. An abraded surface of the paper is often a good indicator that lead has been used.
Conservation treatments available for treating drawings made with lead are very limited because lead is easily destabilised. The faint use of lead can be seen in the detail of the under drawing in XVII/8 Plan of the Chiericati, 1560, shown here.