MITRA Forum Question Details

EditDeleteBEVA 371 is a mixture of ethylene vinyl acetate copolymer, polycyclohexanone resin, phthatate ester, and paraffin wax that has been dissolved in aromatic hydrocarbon solvent(s). (The “B” in BEVA stands for Berger as the formulation was developed by Gustav Berger). BEVA can be purchased as a solution, film, a waxy solid, or a gel. It has been used by conservators since 1970. BEVA 371 adhesive is a waxy solid that contains residual aromatic solvents. It is prepared by diluting it with solvents, allowing the adhesive to dry, and then heating it at a temperature of 65.6 degrees Celsius. BEVA Gel is an aqueous dispersion of ethylene vinyl acetate and acrylic resins dissolved in a cellulosic material. As BEVA Gel has a higher molecular weight than BEVA 371, a higher temperature (70-72 degrees C) is required to activate the resin. BEVA Film is BEVA 371 adhesive that has been cast into a thin film on a silicone-coated sheet of Mylar.

When using BEVA 371 artists should exercise appropriate health and safety procedures. All BEVA products contain a certain amount of aromatic hydrocarbon solvents and some require additional solvents for dilution/preparation. The heat used to activate them can cause residual solvents to off-gas. This is less of an issue with the BEVA Gel; however, the gel can be used in a similar manner as BEVA Film and BEVA Adhesive but tends not to form as strong of a bond. This may not be an issue depending on the weight and/or nature of the canvas support. It is somewhat reversible in water which may counter indicate its use for some circumstances (e.g. if you are using a glue-based ground and/or water-soluble paints). If you are using BEVA film you also significantly limit your exposure to solvents; however, it is often better to use two sheets of film as opposed to one (or even use liquid BEVA in combination with the film) although one sheet may be able to provide enough adhesion. In our experience, liquid BEVA adhesive has provided the best bond. The downside to using liquid BEVA is that you must first follow the instructions to dilute the adhesive which means you will be exposing yourself to more noxious solvents both during preparation and application. Be sure to perform these operations in a well-ventilated area and use protection (a respirator).

EditDeleteI have used both BEVA 371 as well as BEVA 371 film. I use the film for projects smaller than the one described here (on the measure of inches/centimeters) since it is thin and typically works best when applied in one layer. It also provides a quicker solution, since it requires only heat and no solvent drying time, to smaller material application issues. That being said, what is critical in the use of BEVA 371 (gallon) is the application. If one is adhering linen to hardboard, the adhesive may spot through the linen if it is not layered properly with the right consistency. This is more prevalent with a brush coat, than in spraying (flocking) on the adhesive, but spotting can generally be controlled through careful application. As for the bubbles, the key is to mix the solution carefully so air is not whipped into it. Even so, bubbles can occur, but attention to minimizing the bubbles through careful mixing and deliberate application should alleviate many problems.

EditDeleteAnother word of advice/caution from one of our moderators, paintings conservator Rustin Levensen:

What could go wrong with artists mounting finished paintings onto solid supports with BEVA, from the front? They could use too much heat, and with acrylic or newer paintings almost any heat is too much. They could use not enough heat and it wouldn't stick well over time. I am assuming they don't have a hot table, so they could use uneven heat and get melted and unstuck on the same work. In any case, I am hoping they do the mounting BEFORE painting the work. I would think that they would use BEVA film, just because of the solvents. They could make themselves sick with fumes if they use liquid BEVA unless they use protection. And of course, the mess of sticky BEVA everywhere...