ARCHIVAL PROCESSING

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Not Fade Away

Silver photographic images, even when well processed will always be prone to degradation through the ravages of time. The picture above, printed on ‘Barnet’ bromide paper in 1905 shows the tarnishing typical of a print of this age - still a good density range, but a proportion of the image silver has migrated to the surface of the print and plated out as a reflective silver film. Similar effects can happen more quickly and dramatically - frequently the source is close to hand, framing using low grade hardboard with no intermediary vapour barrier layer between the back of the print and the board.

Similar rapid attack can happen in a display environment where there has been fresh painting, and higher than normal heat, light and moisture will always accelerate this oxidation process. From the earliest days image fading was a known problem, and an immediate fix was toning, often with gold salts, but as papers became more robust, sulphide (sepia) toning became prevalent. In the 20’th century selenium toner arrived on the scene, and being espoused by luminaries such as Ansel Adams, came to be regarded as the ultimate finishing treatment for print permanence. This was because selenium did not cause major colour shifts with most papers when used diluted, and as well as improving permanence tended to increase tonal range in a subtle way, and generally enhance the final print. Selenium toner was also widely adopted as a permanising treatment for film records such as microfilm and astronomical plates.