Atmospheric pressure non-thermal plasma cleaning of 19th century daguerreotypes

In the present work, the feasibility of using atmospheric pressure non-thermal plasmas to clean the surface of a corroded 19th century daguerreotype has been examined and a proof-of-principle demonstration is given. The daguerreotype was treated by means of a commercial plasma jet source (kINPen 10, Neoplas Tools GmbH) by different argon-hydrogen gas mixtures (up to 35% H2 content) so as to remove corrosion products, without immersion in solvents and chemicals. The influence of the plasma treatment on the image quality, surface composition and its effectiveness in removing tarnishing products has been evaluated by means of scanning electron microscopy (SEM) with energy dispersive microprobe (EDS) for localized elemental analysis, micro-Raman and ATR-FTIR spectroscopy for phase identification. The main process parameters, critical to achieve an effective cleaning while preventing damage to the fragile image, have also been investigated