LETTER TO THE EDITOR

1.1 To The Editor:

I have seen the article by David Erhardt in the issue, Volume 22, Number 2, Spring 1983 entitled, Removal of Silicone Adhesives. Because Mr. Erhardt was not specific about the types of silicone adhesives he is referring to, it might be helpful if some points which deal with specific silicone adhesives were clarified.

Users of Conserv Art products, namely Fabri-Sil Lining and the liquid silicone adhesive FS2, might be unnecessarily alarmed by what Mr. Erhardt has written. To allay their possible concerns, it should be emphasized that both of these products are provided as specific for painting conservation. Although the silicone adhesives in these products are highly stable, their performance in conservation use on paintings would never require the frightenly harsh methods of reversal described by Mr. Erhardt for other kinds of silicone adhesives.

The silicone adhesive on Fabri-Sil does not harden. Nor, is it soluble in solvents normally used on paintings. It is a non-absorptive contact adhesive that is designed to bond lining to canvas without contaminating the canvas material with adhesive when instructions on the product data sheet are followed properly. It is purposely insoluble to prevent contamination of the paintings during delamination.

Removal of a Fabri-Sil Lining and its accompanying silicone adhesive layer is accomplished by spraying or brushing a naptha-type solvent on the back of the lining in sufficient quantity to be absorbed through the lining fabric. The solvent is then absorbed by the adhesive layer. The silicone adhesive will not dissolve, but it will become gelled, permitting easy removal of the lining by peeling it off. Usually the adhesive layer will come away with the lining fabric. If some spots of adhesive remain on the back of the painting, they will be of a gel consistency, and can be rolled off with the fingers. In the event of excess contact by a solvent, accidentally, the secure bond returns upon solvent evaporation out of the adhesive. Spontaneous delamination will not take place. Physical removal is necessary.

In the case of FS-2 liquid silicone adhesive, the intended use IS that the adhesive be absorbed by the structure of the paintings, deliberately, for internal consolidation purposes. This adhesive is soluble in all coservation solvents. It can be thinned for application by them, or removed by them. It is important to note that the specific solvent for both of these silicone adhesives is trichlorotrifluoroethane. There are several formulations of this solvent. The formula for this specific is CCL2F-CLF2. (It is also important to understand that fluorosolvents are not recommended for delaminations a Fari-Sil lining, because its silicone adhesive will dissolve and become absorbed by the painting, which is contrary to the intended use of Fabri-Sil.)