Cleaning treatment of a tarnished Daguerreotype by using the reducing afterglow of an atmospheric plasma

Daguerreotypes are the earliest artefacts of photography, produced between 1838 and approx.. 1862.  They consist of a copper base plate, with a silver layer on top.  This silver layer was made light sensitive with iodium or bromide and developed with mercury fumes.  The image was in this way produced directly on this metal substrate.  As a consequence, this surface and its image is very prone to physical and chemical damage, mostly by tarnishing in the ambient air polluted with sulphur.  The brown-blue-black tarnishing colours consist of mainly silver sulphides and obscure hereby the image.

The removal of this tarnish or the cleaning is a very delicate matter, since every contact will damage the original surface and image.  Using the afterglow of an atmospheric plasma can offer a valuable alternative technique since it is dry, low temperature, non-contact, no sputtering effects generated and the ability to work in localised areas.

Further research is applied in this field.  Also historical glass negatives and other silver based photographic image carriers are possible to be treated in a similar way.

University of Antwerp – Conservation Studies

Patrick Storme, Olivier Schalm

Before cleaning Right side, vertical orientation, after atmospheric plasma treatment


Details of the above treatment:

Before cleaning:

Spot 1, 50x Spot 4, 50x Spot 8, 500x


After cleaning:

Spot 1, 50x Spot 4, 50x Spot 8, 500x