PVA/PVA Mixture

Images and text by Garry Harrison,
Head, Circulating Collections Conservation,
Indiana University Libraries Preservation Department


PVA/PVA Mixture

Polyvinyl acetate (PVA) is the adhesive used for general work here in our lab. It is a "plastic" adhesive. It is not reversible (in theory, at least), so if work being done involves reversibility issues, Japanese tissue, adhered with wheat paste, is applied directly to the work as a barrier layer. Because PVA is a liquid of high surface tension, its application meets with considerable brush drag. Thus, it is not the adhesive of choice for large surfaces unless board-to-board joints are involved. PVA is used for all such joints.

PVA mixture is a 50/50 mixture of PVA and methyl cellulose. It sets a bit more slowly than PVA, allowing for an extended working time. The methyl cellulose facilitates application by serving as a surfactant, reducing surface tension and thus reducing brush drag. For most work, we use mixture rather than straight PVA because it is easier to manage. Also, for applications other than board-to-board joints, there is no appreciable difference in bond strength between straight PVA and mixture.


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