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Abstract
Barrier coatings are widely used in conservation to add a measure of reversibility to an otherwise irreversible adhesive bond. Barrier materials are applied as thin films to mating surfaces prior to application of a primary (irreversible) adhesive. Subsequently, if reversal is required, the barrier layer can be softened or dissolved, releasing the bonded joint. This investigation was undertaken to determine the suitability of two synthetic resins for use as barrier layers in the bonding of wood with epoxy. The two materials in question, Paraloid B-72 and Paraloid B-67, were chosen because of their potential to be practically reversible in low-polarity solvents. The two polymers were compared, as barrier materials, to two proven barrier coatings, hide glue and Butvar B-98, by measuring their strength in shear according to ASTM D905-98. Investigations were also undertaken to determine the amount of time necessary for barrier layers to dry prior to application of epoxy. Finally the practical reversibility of the barrier coatings was empirically evaluated. Paraloid B-72 was found to be a suitable barrier material in all respects, while Paraloid B-67 failed both strength and reversibility tests.