Stephen P. Koob
The use of Paraloid B-72 as an adhesive is based primarily on its notable conservation qualities, including stability and reversibility. It has very commendable working properties as well, including excellent adhesion and fast setting time, but these can easily be compromised by improper preparation and improper application. This article reviews the many ways that Paraloid B-72 adhesive should be prepared, modified, or manipulated to obtain easy and efficient application as well as consistent and excellent results.
Preparation is critical to having a dependable solvent-based adhesive, and acetone has proven to be the best solvent, as it makes a low-viscosity mixture and a fast-evaporating adhesive, and has very low toxicity. The ratio or percentage of solvent to resin can be modified to allow the conservator to control the application and setting time for different uses. One additive is recommended in the initial preparation, and that is the addition of a small amount of hydrophobic fumed colloidal silica, which aids in uniform application, stabilization of the mixture, even film formation, and slowed solvent evaporation. It is an inert material, classified as a rheological agent (to control flow characteristics).
For use on glass, a thinner solution of approximately 60% w/v is recommended because glass is non-porous and non-permeable, whereas a thicker solution of 72% w/v works better on more porous substrates, such as low-fired ceramics, porous stone, wood, bone, and ivory. To maintain a consistent fluid mixture and optimize application, the prepared adhesive should be poured into adhesive tubes specifically designed for solvent adhesives. This also improves the ease of use and helps to ensure the accurate assembly of fragments.
KEYWORDS: Paraloid B-72, Adhesive, Solvent, Tubes