The restoration of drawings and engravings varies according to the medium used and the problem to be corrected. A look at the two principal techniques that you may need to use.
Dry: use eraser powder to remove the dust. Use circular movements, with your finger or a rag.
Soaking: to minimize stains and rings. Soaking makes the paper fragile, avoid handling the work directly and put it on a larger surface covered in a non-woven support.
--First test the fastness of the pigments by moistening a corner.
--If they are stable, dip the document in a bath of warm water. If they are not stable, bathe it on the surface, design side up.
--Leave it for about two hours, then begin the drying process with a blotter.
--Finish under the weight of a press.
This technique consists of dipping the document in a bath of bleach diluted in water (a maximum of one cupful per liter of water).
Verify the absence of discoloration of the pigments by first dabbing a corner of the document.
Soak for 15 minutes maximum, while keeping an eye on the progress of the bleaching.
Dip it in water for 5 minutes, then in a solution of sodium hyposulphite (to neutralize the chlorine), for about 15 minutes.
Rinse thoroughly: let a thin stream of water run over the tilted surface of the document for an hour to eliminate all traces of the product.
Dry under weight between two blotters.