Linen Backing versus Dry Mounting.

We recently received this question and thought others might also be interested in our answer – especially since dry mounting is such a popular and cost effective treatment for photographs and ephemera.

Dry mounting attaches the poster permanently to a backing board with a chemical spray glue that can be harmful to old paper. Such a process renders the posters almost worthless from a collector’s point of view as the process is very difficult and usually impossible to reverse without damaging the poster. Additionally, dry mounting over time tends to fail, especially in the corners where its common to see “lifting”. For new posters that have no rarity or intrinsic value and can be easily replaced or in situations when the value of the poster is of no interest to the purchaser then dry mounting may be fine as it is cheap and easy to do.

Linen Backing is a process that incorporates the use of acid free wheat starch, acid free lining paper and canvas or linen and most importantly the process is entirely reversible. The method is used by museum conservationists for all types of antique paper restoration and conservation – especially old maps.  An integral part of  the process is de-acidification. Almost all paper, especially that used to make posters, contain natural acids in the pulp from which the paper was made. Over time these acids will eat away at the paper leaving the paper brittle and often stained light brown. Eventually the paper will start to dissolve especially along the fold lines and borders. The rate at which this process takes place depends upon humidity, paper composition and time. During the linen backing we use natural additives that will buffer the action of the acids and prevent further deterioration. Of course, if the paper has already been affected then special baths have to be used prior to linen backing.

Reserving the ability to reverse the process may is important for a number of reasons. For example, a lot of collectors prefer to store their posters folded and in a draw not in a tube or in a frame – usually because they have too may! Some collectors may want to perform additional restoration such as in-painting, washing or stain removal. Ideally this type of work is performed in conjunction with the linen backing, however, conservationists and collectors often differ on how much and what type of restoration should be undertaken. Some collectors cannot afford to pay for a comprehensive restoration at the time of initial Linen Backing and so take short cuts that others may not want to. As posters change hands so do tastes and budgets thereby demanding that the conservation process be reversible.

Finally, it is worth pointing out that posters demand a premium if they have been linen backed, usually selling for 10 -25% more than the same poster in its original folded condition. Most collectors prefer not to see the fold lines and wrinkles which tend to spoil the overall appearance – especially if the poster is to be displayed in a frame.  When was the last time you saw a 40 or 50 year old poster without a small tear or pinhole? Each time you open the poster to show it to a friend you increase the chance of making the tear worse… once linen backed the repairs are healed and the poster is durable and easy to handle – rolled or flat.

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OVMP