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| toning | |
| Barcelona ‘90s Silver print toned sepia (Ag2S) |
| toning | |
| Toning of photographic prints has always been a way or to modify an unpleasant hue (albumen prints, for example, were told to have ‘cheese colour’), or to improve the duration of short-lasting surfaces. Introducing the use of gelatin in the photosensitive emulsions (about 1890) and with a better attention to fix and clearing treatments, toning became mainly a way to make a more pleasant print (by photographer’s point of view) or to imitate other techniques as kalitype, platynotype, or, more prosaically and recently to call to memory “the nice old albumen prints”. The process of toning consists in substituting metallic Ag on the print, with another metal or salt. For the so-called sepia toning, the point is to change Ag in a salt of itself: silver sulfide (Ag2S), wellknown compound by the housekeepers that see it on silver cutlery abandoned for some time to the air oxidation. It’s understood than how this salt is produced from an oxidation of metal silver! To do that, in acceptable time-length from the clever photographer’s point of view, it is necessary to operate — for example — with K ferricyanide + KBr, (the so called bleaching bath) turning the metal in jellowish AgBr, and after that, treat this salt with a solution of sulfide (re-developping bath) to get Ag2S, of a strong sepia colour, that fix itself in place of the previous metal Ag. By toning process it is possible to obtain a good amount of different hues using metals or their salts, as iron or uranium (for reds) nichel (for magentas) ) gold, (for reddish, pink and blues, selenium (purple), and so on. |
Photogravure Photogravure Dichromated gum Carbon process Kallitype Cyanotype Silver print Toning BLACKHOLES heliogravure 2006 WITH-DRAWN heliogravure 2001 Questioni di Stile |
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