Tears, Losses and other Stains - Not infrequently there will be mold stains which appear as black, reddish or brown markings. Often there are tears or losses in the paper, both in the margins and into the image. Acidification of the paper over time contributes to its brittleness, particularly if it has significant wood pulp content, and makes it more delicate and easier to tear. Mold and other stains are usually the result of long term exposure to moisture which also weakens the paper and can eventually cause it to disintegrate. At right is a badly damaged SE print showing significant mold stains and paper tears. Such damage can sometimes be repaired, but unless the image is a particularly valuable one, the cost may be prohibitive.
RSE vs. SE Lithographs
Whether to clean a Roberts print is a matter of individual choice. In making the decision, however, there are differences to bear in mind between the Subscription ("RSE") and Standard ("SE") first editions. (See "How to Identify Different Editions")
Cleaning RSE prints is more expensive and difficult. The paper must be removed from the backing card prior to cleaning, which is a delicate task. Any cleaning method which involves immersion in water (as many do) is problematical for RSE prints, since the hand coloring will tend to fade or bleed and the thinner paper may cockle, wrinkle, or tear. Consequently, RSE prints often require careful handling and cleaning from the back by a professional paper conservator using various solvents and a vacuum extraction table. The cost of such cleaning can be well over $250. For this reason, one should be cautious about purchasing damaged or heavily stained/foxed RSE prints. If the buyer would not be willing to display the print in its damaged condition, and is not prepared to have it cleaned and restored professionally, it may be best to pass it up.
The SE prints are more robust and easier to clean, especially if they have not yet been hand colored. While the paper does have significant wood pulp content, it also has high rag content and is quite heavy. It has retained its strength and, for the most part, its flexibility over the years. The uncleaned SE prints typically show only moderate acidification, usually pH 6.0 or higher. SE prints can therefore be cleaned effectively by immersion in dilute solutions of chemicals which remove toning, foxing, tidemarks and most other stains. While this should also be done by a qualified conservator, it can usually be accomplished economically and with moderate time and effort. Medina Arts offers cleaning of SE prints for a modest fee, and recommends such cleaning before any modern hand coloring is applied. Once colored, the SE lithographs are more difficult to clean without fading or bleeding of the coloring..
The primary object of any cleaning method is to remove the targeted defects without damaging the paper or the lithographic inks. The secondary object is to adjust the pH balance of the paper to counter acidification and thereby prevent or minimize further deterioration.
The most effective methods of removing stains and other defects involve bleaching agents of one type or another, and this is where the problem arises. Many bleaches, particularly sodium hypochlorite (the active agent in Clorox and many other household products), may damage the paper fibers while bleaching out the targeted defects. The print can continue to lighten further over time if the bleaching agent is not completely removed from the paper after cleaning, and if the print is not pH balanced. In the worst cases, the paper may be weakened and damaged, and the image itself may fade dramatically.
Various different chemicals and methods have been evaluated over the years in attempts to avoid or minimize these problems. For some years a chemical known as Chloramine-T was widely used by conservators, as it was thought to rinse thoroughly from the paper after treatment. Recently Chloramine-T has also fallen from favor, and slower, less invasive methods such as exposure to UV light have become popular.
The paper and inks of SE Roberts prints have proven to be remarkably durable, and after research and experimentation Medina Arts has determined that careful pH monitoring and an immersion treatment based on Calcium Hypochlorite is an effective and reasonably safe method for removal of discolorations and deacidification.