If you look at almost any old photograph – especially one that has been kept on display – you will probably see evidence of fading or other deterioration. This is partly because of the general bleaching effect of ultra violet light but damage also arises because of residual light-sensitivity in the silver compounds that make up the image. Image deterioration may not be apparent for many years but prolonged exposure to light, especially where combined with flaws in the original processing technique, will inevitably lead to deterioration.
Photography is now over 170 years old, and the fact that significant numbers of early photographs are still around for us to enjoy shows that long term preservation is perfectly possible, provided we start with the right materials and processes and take a little care to avoid chemical contamination at the processing stage – or any other stage, for that matter – or storage in unsuitable conditions.
If a photograph is to last a lifetime, the first requirement is that it should be printed on good quality photographic paper, preferably on a paper that has a proven track record. The second requirement for archival permanence is that the photograph is properly processed, fixed, washed, and dried. Adequate chemical fixing is clearly important because without it the silver compounds in the image will be unstable, and will remain sensitive to light. Washing must not be skimped because fiber-based paper absorbs large amounts of fixer, and all traces of this this must be removed if the image is to remain stable over a period of many years. Surprisingly, drying methods are also important because excessive heat may cause microscopic cracking of the paper’s emulsion.
To give an even greater assurance of permanence, the image should also be toned. The purpose of toning is sometimes to alter the aesthetic appearance of the image but – even when no change in tone or color is required – toning is still an important stage in the production of a Fine Art Print. This is because, for a high level of permanence, silver salts in the image should be converted into other compounds, with chemical structures that are not unduly sensitive to light.
Most types of mount-board, including the majority of boards available from Art Supply shops, are made from mechanically ground wood-pulp and are not of genuine archival quality. That is to say that, while their appearance may not change for a number of years, the long-term prognosis is that they will tend to become yellow and brittle. Even worse, unless the board is guaranteed to be acid-free (the most basic of archival requirements) the acid content of the fiber may well contaminate the photographic print.
The most satisfactory mount-board material for photographic use is ‘museum’ board. This is made entirely from cotton rag fiber rather than wood pulp and is available in ‘buffered’ form, preferable for most photographic purposes. Photographs should ideally be mounted onto a substantial sheet of museum board and protected by an over-mat of traditional ‘window’ design cut from the same material. This allows an air-space between the print and the glass, thereby preventing ‘ferrotyping’ of the image or the harmful trapping of moisture between the surface of the print and the glazing material of the frame.
The ideal mounting adhesive for photographic use is archival quality dry-mount tissue. It is easy to use, provides a strong bond between print and mount, does not deteriorate with age, contains no chemical compounds which might react with the photograph or mount, and does not support bacterial or fungal growth. Also, in case the worst should come to the worst, the adhesive is ‘reversible’ – in the sense that it is possible for the print to be removed, without damage, from a soiled or damaged mount.
At IMAGE, our Fine Art Photographs are therefore produced to the highest possible archival standards.