Preserving one's prints (entry by Jack Reisland)

Editor's note: The comments you are about to read are a posting that was made by Jack on the [Baren] forum in reply to a question from member Gary Luedtke: What is the interplay of paper discoloration and pigment light fastness over time? How can you tell which is which?

Such a question! Years of research have been done on these questions, and whole books and studies published. I'll try to give the short answer.

Light as a form of energy can act in two ways on both paper and pigments. The first is by directly breaking down the molecule, this is known as photolysis. The power of light to break down molecules is inversely proportional to its wavelength. The shortest wavelengths are the most powerful, and ultraviolet light the most powerful of all. The second is in combination with the environment of the material, including water vapour and oxygen. These two, in combination with light, form substances that age both the paper and pigments. This is known as photo-oxidation. The light energy necessary for this kind of degradation is much lower than for photolysis, so while the removal of ultraviolet radiation by filters is always advised, it must be pointed out that this will not stop many kinds of photo-oxidation. Therefore the reduction of the total intensity of the light on the surface of the print is important to reduce the degradation of the print.

The interaction of paper degradation and pigment fading is a function of the qualities of the paper used, and the kind of pigments on the print, and to a lesser degree some variables such as the sizing and any binders used. The only way to tell the degree of paper degradation or pigment fading is to be able to compare the print to one that has been printed at the same time, and then protected from light. If you are able to determine the paper that the print is printed on, you may be able to get some idea of the amount of 'yellowing' by comparing it to a new sheet of the same paper.

Also, some pigments do indeed turn different colors as they are subjected to light. You must remember that many ink colors are a mixture of different pigments, and those pigments fade at different rates, thereby skewing the tone of the ink as it fades. There is also the possibility that some combinations of pigments can react with each other as they age. Also, some pigments, especially some composed of less stable metal oxides, change colors or oxidize as they age, but these are less in use today for this very reason.

The effect of pollution is generally one of the pollutants combining with humidity or rain to form acid, the familiar 'acid rain', which eats up marble and limestone on contact, making it porous, which makes it vulnerable to freezing and thawing and all sorts of other damaging actions. Fortunately, this is not so much of a problem with prints, although dust settling on a print over a long time can get embedded in the paper fibers and stain it. This, however, is so much slower than photo-oxidization, that it is usually a little too late to worry about.

So, what to do? It would seem that the best bet is to leave them in the dark, except that they are then more vulnerable to mildew foxing and insect damage. Actually, the process that David has suggested is the best treatment of prints. Leave them in an acid free box, to be taken out for viewing (and careful examination for any damage) fairly often. If you choose to hang them, use ultra-violet blocking glass (that preferably does not touch the print), hang them out of direct or bright light, and limit the time that you have them out and framed.

OK, so that wasn't very short, but you should see the long answer!

This page copyright 1999 by Jack Reisland