http://www.kunsthaus.ch/en/sammlung/restaurierung/beispiele-aus-der-praxis/auguste-rodin/etappe-2/retusche/retusche-kupfernitrate-und-schwefelverbindungen/

Kunsthaus Zürich

Touch-ups

The cupric nitrate and sulfur compounds are applied directly on the bleak metal by means of a brush (Photo:  G. Pegurri)
The cupric nitrate and sulfur compounds are applied directly on the bleak metal by means of a brush
(Photo: G. Pegurri)