ALTERATION OF THE VACUUM TABLE DESIGN

5 ALTERATION OF THE VACUUM TABLE DESIGN

RECENTLY we constructed a small portable vacuum table that especially lends itself to leaf casting and pulp filling procedures. It is made entirely of clear plastic, so that when it is placed on a light table, light is transmitted up through the top of the suction box. Permeability of a small part of the upper surface was achieved by drilling many tiny holes in the Plexiglas. Marjorie Cohn suggested at the Milwaukee meeting that a fritted glass plate might be set in the top surface to allow transmission of light without the need for drilling. A full size transparent suction table would be most desirable. Recently, T. K. McKlintoc proposed the use of etched syntered polyethylene as a surface. This translucent porous material, supported by plastic lighting difuser, would result in a device that could serve both leaf casting and conventional suction table needs alike. An illustration of a possible design is shown below (figure 6) .

Fig. 6. A light-transmitting suction table for pulp casting or treatment of a small area.

5.1 Working features of a transmitting suction table

1. A light suction table is extremely versatile. It can serve for leaf casting as just described, conventional pulp filling, and for very precise and selective addition and deposition of pulp.

2. For conventional pulp filling, suction is applied but temporarily blocked by placement of a sheet of thin plastic film over the opening of the table. When proper pulp density and distribution is achieved, the “table cloth” (plastic film) is yanked and the liquid quickly falls, leaving the fibers in place.

3. For certain shaped holes or art that cannot tolerate much wetting, a transmitting table is extremely useful. A dirty edge or a small loss, tear or paper thinning is set on Reemay over the suction area with the vacuum on. Pulp, suspended in very dilute concentration, is dripped onto the damaged area with a wide-tipped medicine dropper. Air flow takes the pulp to the open area and causes adhesion to the edge of the top or to the previously dripped application. It is possible to build up multiple layers until the desired result is achieved without much lateral wetting. It is necessary to send distinct droplets. Attempting pulp application from close range will result in fiber clumping.

6 CONCLUSION

THE LEAF CASTING TECHNIQUE offers a quick and viable alternative to traditional repair techniques. Conducting this kind of procedure on a common suction table increases both the number of artifacts that can be treated and the number of laboratories capable of doing the work. The use of transparent suction tables and silk-screens designed to impart texture to the castings THE LEAF CASTING TECHNIQUE offers a quick and viable alternative to traditional repair techniques. Conducting this kind of procedure on a common suction table increases both the number of artifacts that can be treated and the number of laboratories capable of doing the work. The use of transparent suction tables and silk-screens designed to impart texture to the castings

ACKNOWLEDGEMENTS

THE SUCCESS of this project was dependent on the help and patience of all the people in our laboratory, namely Pauline Mohr, Patricia Morris, Linda Odgen, Sylvia Rodgers, and Janice Mae Schopfer. Special acknowledgement goes to Keiko Keyes. It was through several meetings with Keiko that the original concept was refined and simplified. Finally, this paper became much more readable after the careful attention of Jennifer Futernick.

REFERENCES

Alkalaj, Stella. “The Chemical Laboratory for Hygiene, Conservation and Restoration of Damaged Written Materials.” Restaurator1:2 (1969), pp.87–91.

Wachter, Otto: “Methods of Restoring Old Prints, Documents and Drawings Using Liquid Paper Pulp,” I.I.C. Lisbon Conference 1972, Conservation of Paintings and the Graphics Arts (1972), pp. 971–974.

Alkalay, Esther Boyd. “The History and Development of Leaf Casting,” The Conservation of Library and Archive Materials and the Graphics Arts, Cambridge 1980 Preprints (1980), p. 187.

Petherbridge, Guy. “Analysis, Specification, and Calculation in the Preparation of Leaf Casting Pulp: A Methodology.” The Conservation of Library and Archive Material and the Graphic Arts, Cambridge 1980 Preprints (1980), pp. 189–209.

Keyes, Keiko Mizushima, and Farnsworth, Donald S. “Practical Application of Paper Pulp in the Conservation of Works of Art on Paper.” Preprints. Fourth annual meeting of the American Institute for Conservation (1976), pp. 76–86.

Perkinson, Roy, and Futernick, Robert. “Questions Concerning the Design of Paper Pulp for Repairing Art on Paper.” Preservation of Paper and Textiles of Historic and Artistic Value . No. 164, 1977 (JohnWilliam, editor; published by American Chemical Society).

Weidner, Marilyn Kemp. “A Vacuum Table of Use in Paper Conservation.” Bulletin of the American Institute for Conservation 14:2 (1974).

DuMeer, Robert, “Construction of a Leaf Caster for Small Laboratories.” Preprints. Sixth annual meeting of the American Institute for Conservation , 1978.

JAIC 1994, Volume 33, Number 1, Article 1 (pp. 1 to 23)

AN EXAMINATION OF THE PATINA AND CORROSION MORPHOLOGY OF SOME ROMAN BRONZES

DAVID A. SCOTT

ABSTRACT—The Roman bronze statues of Togati, Roma, and Venus (Demeter) and in the collection of the J. Paul Getty Museum were subject to a detailed technical study. Of particular interest are their unusual, matte, and finely preserved patinas, which closely parallel another bronze, the Nike, in the Cleveland Museum of Art. The bronzes, which date to A.D. 40–68, are described and analyzed and an account of their corrosion is given, drawing on the early work of W. von Geilmann, who examined the corrosion of bronzes from sandy soils in Germany. The patinas of these objects contain substantial amounts of tin oxide and also display warty corrosion. It was postulated, and confirmed by analysis, that patinas of this kind should contain no chloride ions; thus, there are at least two types of warty corrosion of ancient bronzes. The first type, as here, is chemically stable and does not necessarily require strictly regulated humidity conditions. The second type of warty corrosion is related to the presence of chlorides, usually with an accumulation of cuprous chloride. The three bronzes studied here are closely related and are almost certainly from the same burial deposit, as evidenced by their associated soil and minerals. These materials were not completely cleaned from the surfaces of the bronzes, so essential information regarding their origin was preserved. Cleaning during conservation to a uniform “original surface” or “marker layer” would have removed this important evidence.