Hampton Photo Arts

The progressive yellowing of a print can be slowed down by a kind of bleaching of the sheet of paper. This is a very delicate operation which requires immersing the print in a solution. Such a "bath" is only possible if both the paper and the ink take well to it.

Such baths are usually given to engravings and lithographies printed with oil based inks and that have not been coloured with water based colours. The print must first be immersed in clean, cold water so as to wet and wash the paper. The print is then placed between two white blotting papers and a second or "bleaching" bath is given.

Bleaching is done using a variety of solutions:

1. Use a solution made of one part of water and one part of hydrogen peroxide to which a few drops of ammonia are added. Rinse the print several times with cold, clean water. The final rinsing should take about one hour.

2. Bleach and water may be used in equal proportions but it is best to begin with a 10% solution reinforcing it a little at a time until the solution reaches 50%. However, bleaching water must be used very cautiously because it can affect the strength of the paper after some years. The great danger is that the chemical will not be entirely washed out of the paper after use. It requires hours of soaking in constantly changed water to ensure that none remains. The solution should always be very weak.

3. Another system employs small amounts of sodium crystals. This solution is just as powerful as bleaching water but it is less dangerous. Several rinsings must follow the bleaching. This solution is made with 20g of pure sodium chloride for each liter of water to which a few drops (25 ml) of formaldehyde are added. This solution is particularly efficacious because the bleaching is done by emanation. The print is then rinsed thoroughly.

4. Another way of bleaching a print is to use 20g of chloramine T in one liter of water or 40g of sodium hypochloride in one liter of water. The latter requires a tepid neutralizing bath that contains 20g of sodium thiosulphate in one liter of water.

Local bleaching can be done by using the above mentioned solutions applied with a brush. Each spot can be dabbed with a hydrogen peroxide solution. These solutions can be also vaporized onto papers that cannot undergo total immersion. Industrial methylated spirit is particularly well suited for all types of papers that must not be dampened. The drying that must follow these bleaching and rinsing baths should be done in a press, placing the print between two sheets of blotting paper.

Damage to the tones Restoring damaged tones is technically complicated and a very delicate task as it requires a very light hand, good taste, and a good dose of modesty. To avoid artificial appearance, specialists should limit their work to the reconstruction of missing parts, to gluing rips, and to bleaching the paper. Only at times, and very discreetly, should they restore a faded area with faded tones or maybe even generally brighten up the print by touching it up very slightly. However, faded colours should never be retouched. What must be sought after is a general balance of tones and lines rather than an hypothetical original state that, in any case, can hardly be recreated.

Damage due to smoke and dust Prints that have been exposed to smoke and dust are often dirty and gray. Cleaning always begins with a dry method using compressed bread crumbs which absorb dust very well. After both sides of the paper have been cleaned, the crumbs are then brushed off. Erasing is sometimes done with a soft eraser limiting its use to outer areas of the print, as finer lines of the print can be affected. The eraser is usually cut in such a way that small areas can be reached. Hard, abrasive erasers must be avoided or used very carefully only on certain spots and on well sized paper.
Incrustations of foreign matter can be removed by scraping with a razor blade or any other sharp instrument. If this first cleaning is not sufficient, proceed to the wet cleaning method, making sure that the paper and inks will take well to washing. Spots can be removed or at least considerably lightened by dabbing these areas with a brush and clean water or a diluted bleaching solution. Total immersion in clean water is often practiced on engravings since they usually take well to such treatment. The print can also be washed with a very diluted chlorine solution for a few seconds and then rinsed thorouqhly in water.

Damage due to humidity The damage done by humidity is one of the most ruinous for prints not only because it favours the growth of bacteria but also because it will make the paper buckle, dissolve the sizing, destroy the assembled pieces (glued backings, etc.) and provoke the formation of spots and water marks. In damp conditions prints can easily become affected with mildew, a superficial coating or discoloring of paper caused by fungi. The mildew feeds chiefly on the size in the paper and by the time the discoloration produced by the dead fungus has been removed the size has practically disappeared too, leaving the paper, to all intents and purposes, as soft and absorbent as blotting-paper. A really good, strong fibred paper will stand this, but a poor fibre relying upon the size for its strength would naturally go to pieces at once. Though the absence of size may make other papers less liable to the growth of mildew, the moisture they will contain will aid its germination. It is not uncommon for a collector to notice mildew (recently started) and to find out soon that the marks have disappeared when the print has been exposed to dry air for a short time. Sunlight and even the dryness of a living room will often check the continuance of growth, but the mildew is not dead. It is still in the paper, and will renew its activities at once if favourable conditions are restored. To kill the spores, chemical treatment is essential. Even paper upon which there are no signs of active mildew is better treted if there is reason to suspect contamination. There is no need to place a print in formalin bath. A sponge or large brush applied to the back is all that is necessary. If a print has undergone excessive humidity, the spots are not easy to remove. The print can be washed either partially or totally, depending on the size and amount of the spots. The spots can be treated by dabbing them slightly with a cotton tip or a brush dipped in bleaching solution. Any wrinkling can be lessened by dampening the paper and then drying it under pressure. Any gluing, backing up and framing should be done only after the print has dried properly.