Bookbinding and the Conservation of Books
A Dictionary of Descriptive Terminology

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heat-set tissue

A lens tissue especially prepared for use in mending tears in paper, strengthening margins, and for laminating weak or badly torn leaves, by means of dry application rather than by the traditional aqueous application. The tissue is made of pure cellulose consisting of more or less lOO% rag content, no coating or additives, and a pH of 7.0. The tissue is not structurally uniform in texture, consequently there are small random open spaces and some bunching of fibers. Although its thickness is presumed to be approximately 0.0015 inch, this can vary from one batch to another, although it does not normally exceed 0.002 inch. The tissue is coated on one side with an acrylic resin. It is applied to both sides of tears, but to only one side of a weakened leaf, provided that no adhesive is exposed on the other side. The tissue is tipped on the leaf with a warm iron (approximately 100° F.), and then pressed on firmly through terylene or a textured paper. The iron is not pressed directly on the heat-set tissue because this might result in blocking and may also impart a sheen to the tissue, thus making it more noticeable.




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