Readers of the following article should bear in mind the distinctions between presentation, preservation and restoration, each of which will bring separate considerations when deciding what to do with a poster. The purpose here is to discuss various methods of poster treatment with an emphasis on preservation. Some poster treatments, such as linen backing or framing, have more value as methods of presentation than as methods of preservation. Restorative techniques, such as flattening folds, repairing tears and infilling missing paper and art, can be independently considered. They can be a part of any strategy for handling posters, regardless of whether the emphasis is on presentation or preservation.
In financial terms, vintage movie posters are generally recognized as an attractive investment. The quantities are limited, and the practice of collecting movie posters is still relatively new. As the hobby grows in popularity and the more desirable posters become more difficult to obtain, values seem certain to continue to rise.
Yet the posters themselves are paper display items that were never intended to be kept or collected (such things are known as "ephemera"). They are fragile and very perishable. If they are to be kept in good condition for posterity, they must be carefully preserved, using modern techniques of paper conservation. A treated and protected poster will be both more attractive to display and less vulnerable to damage during handling and storage.
All current paper preservation methods have at least one essential element in common: pH testing, and, if needed, chemical stabilization and deacidification. The other major element of paper preservation is the protective cover, for which there are many variations.
The acids present in most industrial papers made since the early 19th century are the primary cause of age deterioration. Unless something is done to arrest the process, sooner or later these acids will simply devour the paper, causing it first to become weak and brittle, and then eventually to crumble. Only deacidification can arrest this process. Fortunately, solvent-based deacidification solutions are readily available today. If found to contain acid via pH testing, a poster or other paper document can be deacidified easily and quickly with a spray bottle or a brush. These will also add an alkaline base to the paper.
After deacidification, there are three common approaches to long-term storage and preservation:
1) Backing the poster with linen, canvas or some other resilient material
2) Lamination
3) Encapsulation
Of these three, the one most commonly seen today among movie poster collectors, and perhaps the best one from the standpoint of presentation, as opposed to preservation, is linen backing. Linen-backed posters are quite attractive, and are often seen at auctions featuring rare and expensive specimens. This linen backing, usually with a paper interleaf between the poster and the backing, also provides a durable base for the restoration of any missing parts of the poster, using paper patches and fill-in art work. The heavy linen base also greatly reduces the likelihood that the poster will be torn through careless handling.
Yet despite its cosmetic and tactile appeal, linen backing has some major drawbacks. It is expensive, costing anywhere from $50 to over $100 for a single poster. It is time-consuming, requiring a wait of 4 weeks to 3 months at most of the studios now offering the service, and it leaves the front of the poster exposed to spills, scratches or other surface damage. Moreover, in the view of most paper conservators, linen backing presents a potential danger in the long term because the linen and the paper, being fundamentally different materials with different responses to air, chemistry, humidity and temperature, are likely to go their separate ways over time, causing a rupture in the binding that could even damage the poster. Such a change, if it did occur, would take many decades, but if the goal is permanence, linen backing may ultimately fail to meet the scientifically established criteria.
Another potential problem is reversibility. Most of the linen backing processes now in use are said by their manufacturers to be reversible, meaning that the linen can be safely removed from the poster if desired. While this may be true now, it cannot be proven that the reversibility will not end at some point. Linen-backing substrates have only been in use a few years. No one really knows whether the adhesives used to apply the backing will still be removable 50, 100 or 200 years from now. Yet for some posters that are seriouly damaged, linen-backing may be the best way to make the piece presentable again.
Lamination refers to the application of a clear coating to the front and back of a poster. Like linen backing, lamination is a choice that favors presentation over preservation. When done with a view to preservation, lamination is usually done with a tissue paper laminate applied in a heat press, as opposed to the plastic laminates used for such things as wallet cards and name tags. The manufacturers of the tissue laminates have designed them to be removable with mineral spirits. Another popular tissue laminate is made of nylon, but because nylon and paper are different in nature, most preservationists prefer to use tissue paper laminates on posters and other paper items. Lamination provides excellent protection and may be desirable if a poster is to be handled a great deal. Its disadvantages are that, like linen backing, it may present a long-term risk to the poster if the reversibility fails, and, while present, the lamination makes a slight visual change to the paper's original color and contrast. Where a poster or document is to be handled frequently, however, lamination is a good way to give durability and convenient access, and it can also be applied to the back of a poster at very little risk to repair tears and flatten creases caused by folding. Despite the improved materials and the excellent protection afforded to paper by the tissue paper laminates, most paper preservationists do not recommend this procedure where the primary goal is preservation.
The safest and most effective long-term paper protection method known today is encapsulation. Encapsulation is also quite attractive physically and considerably less expensive than framing or linen backing, although an encapsulated poster could still be framed if desired. Moreover, if presentation improvements such as flattening creases and the restoration of missing paper and art are desired, these procedures can be done prior to encapsulation. It is the only one of the three preservation techniques whose use does not foreclose other options.
Encapsulation is a technique developed by the Library of Congress for the long-term preservation of rare and valuable sheet documents. It is done in two steps. First the item is chemically stablized and deacidified, and then it is sealed in an acid-free polyester enclosure. The polyester (Mylar) capsule is a tough, clear and attractive material that can withstand routine handling and moving for many years. The seal keeps the item dry and free of contaminants, while the transparent polyester allows the paper to be viewed from both sides. The polyester capsule itself is not attached to the paper in any way, and thus the poster can always be safely removed. The only loss in the event of removal would be breakage of the seal, but the unsealed capsule could still be reused as a protective sleeve.