Charcoal and sanguine can be counted among the most friable media used by artists. While this kind of technique may be fixed by the artist, fixing is not generally recommended as a conservation treatment as it can alter the appearance of the media. Therefore, the conservation of charcoal and sanguine drawings can be very challenging.
In this case, the drawing was only partially fixed which made it unsuitable for a regular washing. Nevertheless, the discoloration of the paper was strong enough to attempt to remove at least part of the discoloration that the paper suffered.
The cleaning of the paper was performed with the wet blotting technique. This procedure is based in the capillarity forces created between the original support and the blotting papers. Initially, the wet blotting papers transmit the humidity to the original support. Afterwards, by adding a dry blotting paper underneath, the attraction of the water to the new blotter moves, not only the water but also part of the discoloration products present in the paper. This operation needs to be repeated several times until the desired results are obtained.
In this case, after the conservation of charcoal and sanguine drawing, the paper was substantially lighter allowing for the chromatic values of the drawing to be seen.