Volume 3, Number 1, Feb. 1981, p.2

Technical Exchange

Removal of Oxidation Products from Metallic Threads

Has anyone used a jewelers fiberglass bristle brush for polishing metals to remove oxidation products from metallic threads couched onto textiles?

I have found this method of mechanically cleaning metallic threads encrusted with dirt and oxidation products preferable to using chemicals which may harm the surrounding fabric and the silk core threads around which the metals wrapped.

The accompanying photograph shows a silk velvet with padded and couched silver metallic threads typical of many textiles in the collection of the Skirball Museum of the Hebrew Union College. The bristle brush is not effective on "gold" metallic threads as these actually are a wash of gold over silver base which will abrade even under the lightest stroke. More on the pros and cons on the use of the brush are reviewed in "A Dry Method of Cleaning Metallic Yarns and Ornaments In Textiles," Margaret Craver Withers et al.; Studies in Conservation, August 1964, Vol.6, No.3. If anyone has any comments on the use of the fiberglass bristle brush for this purpose, please contact me: Janet N. Davenzer, Textile Conservator, H.U.C. Skirball Museum, 3077 University Avenue, Los Angeles, CA 90007, (213) 749-3424. The fiberglass bristle brush is available from: Friedheim Tool Supply Co., 412 W. 6th Street, L.A. 90014, (213) 624-0731. catalogue number 184-2.

Sources for Hard-to-Find Chemicals

Private conservators often find it difficult to identify sources for reagents and other exotic chemicals cited in the conservation literature. Local sources often do not stock such materials because of the limited demand. Most manufacturers will supply, free of charge, samples of their specialty chemicals to any person, organization, or interested group which the manufacturer feels will eventually help the distribution and extension of its market. They will also provide any technical data requested. The two standard references for manufacturers of exotic materials (as well as common ones) are:

1. OPO Chemical Buyers Directory. published by the Chemical Market Reporter
2. Chem Sources--U.S.A., Directories Publishing Co.. Inc., Flemington, N.J. 08822

These reference books are relatively expensive so the conservator is advised to ask his/her local chemical retailer to provide the information. This they should gladly do. Two other sources for paper conservators which may be of value in the investigation of enzymes are:

1. Cal Bio Chem.. P 0. Box 12087, San Diego, CA 92112
2. Nutritional Biochemical, 3127 W. Lake, Chicago, IL 90912

Reconstruction of D. Sherrin's Painting Techniques

A painting of very unusual construction has recently been brought to the Los Angeles County Museum of Art for conservation. It is entitled "Scottish Moor With Cattle," and is signed "D Sherrin".

The painting is executed on canvas. Its unusual feature is its paint film structure. The picture is basically painted in drying oils. This, of course. is not remarkable. Over the oil layer, however, lies opaque, matte, water-based paints. The latter are very carefully and selectively applied, and are meant to enhance the oil-based design. For example, additional blades of marsh grass in the water-soluble medium are added to the marsh grass done in oil. The care taken in applying the water-based paint and the similarity in handling of both paint layers suggests that D. Sherrin himself applied the water-based paints to the oil layer. A search of the an historical literature and of Art and Archaeology Technical Abstracts shed no light on the painting techniques of D. Sherrin. Nor were any of his paintings mentioned. Perhaps one of the members has information about D. Sherrin and his paintings. If so, I would appreciate learning about this artist and his work. Please write to: Laura J. Juszczak, Conservation Center, Los Angeles County Museum of Art, 5909 Wilshire Blvd., Los Angeles, CA 90036.

Cushioning for Vacuum Hot Table Linings

Conservators lining paintings on the vacuum hot table are constantly faced with the problem of avoiding weave interference from the lining fabric or fabric texture from the reverse of the original support in the front surface of the lined painting. Various types of cushioning materials [blotters, felt, satin weave fiberglass) and interliners have been used with a moderate degree of success as a means of reducing this problem.

At BACC we have been using silicone rubber sheeting as a cushioning layer on our vacuum hot table and have found that it is quite effective in minimizing or preventing weave interference and/or fabric texture. The material is "Cohrlastic" silicone rubber sheeting, 9200 series, 1/16" and 1/32" thick, made by the Connecticut Hard Rubber Company, 407 East Street, New Haven, Conn. 06509 (203-777-3631). The use of this sheeting was suggested several years ago by Gerald Hoepfner as a cushioning for lining paintings face down. Further experimentation with it also indicated that if used with relatively low vacuum pressure it could be effective cushioning for lining or infusing paintings face up. The silicone rubber sheeting is very strong and durable and not affected by water or mild solvents. It comes in various degrees of hardness but so far we have only used the 30 durometers variety. It has a strong resistance to "compression set" so impressions in its surface made by thick paint when lining face down disappear almost immediately.

The drawbacks of the sheeting are that it is only available in 36" widths which limits its use somewhat, and it is also quite expensive. The material can come from the factory with flaws which make it unacceptable for our use, so it should be inspected very carefully in raking light before use. However, our local sales representative was very cooperative about replacing the flawed piece of sheeting with a perfect piece. The company manufactures a wide variety of silicone rubber sheeting materials but the cost has prevented us from experimenting with anything other than the 9200 series. We would be interested in hearing from anyone who tries any of the other types of silicone sheeting.