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Following article posted Jan. 28, 2000, Vol. IV Number 03 
Contributed by: Audrie Schell, Schellaj@mcmaster.ca Adhesive Tapes - Friend or Foe? Adhesive tapes, known as pressure sensitive tapes in Conservation, are often considered an ideal method for mending damaged or torn papers. These tapes are applied with hand pressure and stick aggressively to most surfaces. Because of their low cost and ease of application, pressure sensitive tapes have gained wide acceptance. However, despite manufacturers' claims, tapes should never be applied to important papers, manuscripts or maps due to their degradation properties over time. Pressure sensitive tapes consist of two main elements: the backing and the adhesive. Tape backings, or carriers, can be made of plastic film, fabric, paper, metal foil and other materials that provide a flexible support for the adhesive mass. The two general classes of pressure sensitive adhesives are those made from rubber and those made from synthetic polymers. No matter what its composition or the formulation of its adhesive, the long term sticking power of pressure sensitive tape does not come from the initial pressing of tape to paper. Initially, due to the tackifiers present, a strong, Velcro - like bond does occur but long term adhesion occurs through secondary bonding an interaction between the adhesive and the paper. In the earl stages of ageing, deterioration is slow, adhesion is weak and the tape can be easily removed by mechanical means. Continued ageing makes removal more difficult and places the item at risk as various chemical processes work to undermine the structural integrity of the substrate. Staining and translucency of the paper begins to occur, often obscuring information and causing media to bleed. As time passes, this staining will become a permanent feature. Another degrading property of pressure sensitive tapes is that over time, the adhesive loses its ability to slide and flex thus becoming set and rigid in its structure. This attribute renders an item structurally unsound. The paper substrate cannot adequately support this type of rigidity and the result is further damage to the item. Maintaining the original condition of any item is of utmost importance and for this reason, mending with pressure sensitive tapes should be avoided. Rather than repairing torn documents, one can house the damaged item in acid -free envelopes or Mylar sleeves. Larger items can be stored in acid -free boxes. Books may be boxed, slipcased or wrapped in strong, acid - free paper. Repairs to damaged items should be left to a qualified Conservator. Contributed by: Audrie Schell - Schellaj@mcmaster.ca Jan. 21, 2000. Editor's Note: Audrie Schell, a qualified conservator, lectured on preservation of paper documents at the 1999 Global Family History Fair in Milton. GlobalGenalogy.com carries a wide range of presevation supplies, some of which are listed at http://GlobalGenealogy.com/archival.htm
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