BEVA 371 AND ITS USE AS AN ADHESIVE FOR SKIN AND LEATHER REPAIRS: BACKGROUND AND A REVIEW OF TREATMENTS
LISA KRONTHAL, JUDITH LEVINSON, CAROLE DIGNARD, ESTHER CHAO, & JANE DOWN
In the early 1970s, a new adhesive named BEVA 371 solution was introduced to the field of art conservation. Created by Gustav Berger, the material was originally developed as a consolidant and lining adhesive for paintings and was meant to satisfy several requirements. These included chemical stability, nonaqueous qualities, strong adhesion properties in combination with a variety of substrates, relatively low activation temperatures, minimal pressure necessary during application, ease of removal, minimal effect on original drape of textile substrate, and negligible staining of delicate materials or absorbent paint films.
Following the success of the original BEVA 371 in solution form, other BEVA products were developed, including BEVA 371 film in the late 1970s. The film consists of the original BEVA 371 formula produced as either a 1 or 2.5 mil thick film sand-wiched between silicone release paper and silicone release Mylar/Melinex (Berger and Russell 2000). Although of the same chemical composition, the different physical forms of the solid film and the viscous liquid solution as well as the presence or absence of solvent are important distinctions. These differences allow for a variety of preparation procedures and methods of applications, resulting in different qualities of a lining or repair. During development of the film, Berger (1976) mentioned that such a self-supported film could make it easier to apply and to remove BEVA 371 from fragile textiles and paper without impregnation or staining. Currently, BEVA 371 solution and film are among the most commonly used adhesives in paintings conservation.
For clarification purposes, it should be noted that the original BEVA 371 solution is referred to in the literature not only as “BEVA 371 solution” but also simply as “BEVA” or “BEVA 371” (Berger and Russell 2000). BEVA 371 film is often referred to as “BEVA film” or simply “BEVA.” BEVA D-8 dispersion, BEVA gel, and BEVA gesso are other BEVA products commercially available (Berger and Russell 2000). This article will focus on BEVA 371 solution and BEVA 371 film, and the term “BEVA 371” will be used to refer to both.
Though originally conceived in the context of paintings conservation treatment, over time the use of the two BEVA products was transferred to textile and objects conservation. They are often used as backing adhesives for repairs on skin and leather in North American museums, reflecting original lining applications used in paintings conservation. However, the nature of the materials to which they are applied and the methods of application used are different, which is not surprising, since skin and leather objects are quite different from canvas paintings. They are not usually under tension, they are often three-dimensional, and they are nonwoven. In addition, leather and skins can be highly acidic. Though the normal pH range of vegetable-tanned leather—3.5 to 6.0 (Larsen 1994)—is comparable to the pH of 3.5 to 5.5 of aged canvases (Hackney and Ernst 1994), it can be as low as 2.5 in the case of acid-deteriorated, or red-rotted, vegetable-tanned leather (Larsen 1994). Thus, the BEVA 371 used to back degraded leathers could be in intimate contact with a more acidic environment than when it is used to line deteriorated paintings.