If you love books and try diligently to take care of them, it can be distressing to find that the pages of some of your classic collectibles no longer look pristine. You find you are downgrading their condition from good to fair, just because of the brown spots (also called foxing), yellowing, or browning over the pages.
Because browning can be the result of several things, stopping browning is dependent upon a range of tactics. Before trying these solutions, it is important to consider the underlying value of the book. The more valuable the book, the more important it is to choose the process carefully.
Preventing the brown discoloration that tends to appear on older books is only half of the process. There are tips to prevent the pages from deteriorating. There are also a few measures to remove the unwanted coloration, but generally, reversing the process may be a challenge.
8 ways to prevent browning
Because of the underlying causes of browning and foxing, it may be difficult to prevent these conditions from developing. There are some common sense tips for storage which apply to all books. The age of the book and its existing condition will affect the way it is handled, and its storage environment. The following tips are relevant to all types of storage environments for books, regardless of the condition.
The room or area where books are to be stored should be cool and dry. Central air is better than fluctuations which come from other types of heating and cooling. It is important to stabilize the temperature as much as possible, so there is minimal variance in the ambient temperature.
The air in the room should be replaced on a regular basis for best management of the environment. Moving air, especially when filtered at some level, helps to reduce the variations in temperature which can happen with still air. Good air flow also helps to limit the growth of mold, which can be a factor in the development of foxing.
No direct sunlight/UV exposure
Keep books out of direct sunlight. Placing books in an area where even a few minutes of direct sunlight fall on them daily will quickly lead to visible signs of deterioration. The bright colors will fade, and the paper will deteriorate as it dries out. Ultraviolet rays from the sun can create damage of other types, as well as fading.
Avoid placing houseplants in a library room or on bookshelves
The plants themselves are not harmful to your books, and do not cause deterioration directly. In fact, live plants in many interior spaces are a positive element from a decor standpoint. The problem with plants is that they need to be watered. This can contribute to the humidity of the indoor space and can affect the condition of the books.
If plants are included in libraries and other reading spaces where books are also present, they should be limited to succulents, cactus, and similar plants that do not require much water. Plants that need sunshine and books that should not be placed in direct sunlight are not a good mix.
Control the humidity
The humidity levels should be maintained between 50% and 60%. This level is not too damp and not too dry. Humidity and warm temperatures together create a perfect environment for the growth of mold and mildew – exactly the combination that you don’t want.
Use acid-free archival paper
Place acid-free archival paper between the pages of your most valuable and treasured volumes. This product is designed to absorb acid from the pages. It helps to prevent damage due to browning.
Regardless of how carefully you clean your house and specifically where books are stored, there is always going to be a steady build-up of dust, organisms and other elements you don’t want on your books. Regular dusting will help to remove spores which can damage the paper of your books. Remove the books one at a time from the shelf and dust all surfaces, as well as the shelves themselves. Use a lint free cloth or product to avoid damage to the binding.
Wash your hands
Valuable books and documents, whether they show signs of browning or not, should always be handled only with thoroughly washed and dried clean hands. If you suspect that the books may be exposed to mold or other health hazards, you should wear nitrile or vinyl gloves to handle the books.
What causes brown spots on books?
There are several theories which have been put forward about the causes and results of browning, foxing, or discoloration in books. These theories include mold or fungal growth, oxidation of iron, copper, metallic or organic contaminants in the paper, humidity, and lignin content of paper.
Mold or fungal growth
Some foxing is likely caused by the action of mold or mildew. This occurs when the enzymes utilized by the organisms break down the structure of the paper. The brown staining is the result of the residual dead mold or mildew and also by the deterioration of the substrate. Mold feeds on the paper itself. It also feeds on any organic material or dirt on the paper, such as finger marks, squashed insects, or food stains.
Oxidation of iron, copper, metallic, or organic contaminants
The chemical origin of foxing is thought to be due to the fact that iron ions Fe(II) and Fe(III) and other contaminants catalyze the oxidation of paper, yielding the yellow-brown stains. In fact, one theory of the origin of the term ‘foxing’ is from Fe (the symbol for iron and OXide. Another theory is that an observer looking at the pattern said it looked like the muddy footprints of a fox across the paper. It could also be the reddish color of some of the browning.
Maintaining a moisture level which is around fifty to sixty percent is standard practice in libraries. Foxing in some instances is due to a reaction with fungal spores and moisture. Foxing may begin as a small and easily overlooked blemish that will spread and become worse once it becomes established.
Lignin content of paper
Lignin is a complex organic polymer that, along with cellulose, forms the chief constituent of wood. It is the second-most abundant organic material on Earth. Early papermaking in Europe used flax, hemp, and cotton (which are low-lignin and high-cellulose in content) rather than wood pulp. Earlier European papermaking also used calcium carbonate, which helped neutralize acids. Newer books, particularly mass-market paperbacks, are often printed on cheap paper, with 20% lignin. The change to higher lignin content is one reason why foxing affects more recent books worse than older books.
Alum-rosin size is a dilute washcoat sealant used to make paper surfaces clearer for printing. It was used from the mid-19th century, cheaper than earlier glue-based sizing, but not as chemically stable. It breaks down in moist conditions, producing sulfuric acid and yellowing pages.
The growing demand for paper to feed printing presses developed in the mid 1400s. England began producing large supplies of paper in the late 15th century. The earliest European paper mills used the Chinese method of shredding rags and clothing into individual fibers to make paper. As the demand grew, the mills changed to using the fiber from trees. Longer fibers in older paper-making processes are more durable than shorter fibers typical from industrial mechanized paper-making processes used in more recent times.
Beginning in the late 1800s and onward many books were produced using wood pulp paper. Paper from untreated wood pulp releases several types of acid, including oxalic, acetic, lactic, and formic. Accumulation of acid causes staining and eventually deterioration of paper.
How to reverse foxing
Conservationists and paper or book restorers typically use a range of chemical or plant extract treatments to attempt to neutralize the reddish stains associated with foxing. Removing ferrous oxide (FeO) from the paper appears to be a key step in both removing the stains and preventing their recurrence.
Where appropriate, mold needs to be physically removed from paper and book surfaces first, typically by gentle brushing, wiping, or HEPA vacuuming.
Dozens of treatments have been used, or proposed to reverse the effects of browning, These range from lasers at specific frequencies, microwaves, and washes composed of neutralizing agents. The challenge of using such methods is that there is a risk of destroying the inks while treating the paper. Given the scarcity of ancient manuscripts, no one wants to ruin a valuable document through improper techniques.
Some older documented treatments for foxing stains on paper, photographs, books, or other similar products are both obsolete (no longer recommended) and dangerous. It is also true that while some of the techniques make the paper look better for a time, the stains can return.
Large book archives, like the U.S. Library of Congress, use deacidification treatments to extend the life of books made with acidic paper. Usually deacidification involves neutralizing the acid by adding an alkaline component, like chalk, to the paper.
While the words in the oldest pages and books can be captured, the books themselves are constantly under the ravages of environment, careless handling, improper storage, and lack of knowledge. Poor choices in the past have led to a growing number of books which cannot be used by anyone but conservationists and then only in the most stringent of environments.
Foxing and browning are symptoms of the deterioration of some of the oldest books, as well as many more recent volumes. Cheap paper and the printing press initially made books available to more people, but these same books are now almost unavailable to the general public.