Covering a pair of practical case studies, Claire Winfield’s presentation on her recent uses of Butvar® B-98 was clear and informative. Winfield, the Associate Painting Conservator at Saint Louis Art Museum (SLAM), featured two artworks that share the characteristic of having friable matte paint, but the process and purpose for consolidation of each one varied. Her ability to modify her approach for each situation was guided by research and first-hand tests with Butvar® B-98.
Butvar® B-98 is one of a series of trademarked polyvinyl butyral resins, which are valued for their clarity, adhesion to varied surfaces, rheology, toughness, flexibility, and aging characteristics. Butvars® are available in a range of molecular weights (MW) and can be applied in a variety of solvents by brush or spray. They are typically used in objects conservation for materials such as deteriorated wood, stone, plaster, bone, fossils, and baskets, because they can retain a matte surface and cause little color saturation.
In both of Winfield’s featured treatments, she needed to stabilize paint without altering its optical properties – a steep challenge given their powdery surfaces. Winfield focused on the energy relationships between Butvar® B-98 and the painted surfaces, reducing the adhesive’s particle size (B-98 is the lowest MW Butvar® available) and spray applying it in multiple dilute coatings to promote penetration. Keeping the spray tip completely clean and pre-wetting the surface with solvent were helpful in this process.
The first case study was Enforcer (1962) by Larry Poons, composed of Liquitex acrylic paint and Fabspray on canvas. The Fabspray, a spray paint for fabric with vinyl and alkyd resin binders, unfortunately aged very poorly, having deteriorated to the point of actively shedding pigment. The goal of treatment was to keep the paint in place for safe dusting of the surface. Adhesive tests included Butvars® of varying weight, gelatin, and methylcellulose. Due to its small particle size, low viscosity in ethanol, strength, and minimal visual effect, a 1% Butvar® B-98 in ethanol was chosen as the consolidant. Since the Liquitex and Fabspray were applied to the painting in discrete areas, it was possible to mask the Liquitex areas while spray applying six coats of dilute consolidant to the Fabspray. The results were successful in that the paint no longer actively sheds and remains visually matte; however, the surface still cannot be safely dusted, and there was a slight but acceptable saturation of the color.
Micenic (c. 1942) by Siegfried Reinhardt, an oil painting on pressed board, was the second case study. The paint layer was locally cracked and lifting away from the board, and it was also lacking in cohesive strength: the lifting paint crumbled from brush contact and could not withstand heat. Following tests, the surface was pre-wet with 60:40 toluene:ethanol then then sprayed overall with 2% Butvar® B-98 in the same solvent mix to give the paint cohesive strength. Ethanol helped lower the viscosity of the adhesive, and toluene prevented tidelines caused by the paint’s slight ethanol sensitivity. BEVA® 371 in naphtha with heat assistance could then be applied to readhere the lifting paint to the board without undermining the cohesion provided by the B-98. This two-layer consolidation process successfully preserved both the structure and appearance of this painting.
Winfield’s work provided two responsible and creative examples for how Butvar® B-98 can be a useful addition to a paintings conservator’s toolkit.