Sculpture: The Ammonia Plasticization Process for Bending Pieces of Wood

Leottctrdo, Vol. 10, p. 54-55. Pergamon Press 1977. Printed in Great Britain SCULPTURE : THE AMMONIA PLASTICIZATION PROCESS FOR BENDING PIECES OF WOOD Henry P. Raleigh* and Dennis Connot%** Bending wood by the steam process is common enough in furniture manufacture, but it is rarely used for making sculpture in the U.S.A. Instead, the slow, timeconsuming and expensive technique of lamination generally has been adopted for sculpture with curved elements of wood. The troublesome features of working with steam-softened wood have been the difficulty of holding a piece of it with jigs or clamps, the tendency. especially pronounced when complex curved surfaces are involved, for it to retain a degree of 'memory' of its original shape upon drying and, not infrequently, for it to crack during drying. In the process described here ammonia gas is employed in a manner similar to that used in ;I small steam-bending plant and several advantages are realized. Since ammonia gas (NH,) under pressure at temperatures of about 70 F (21-C) is ;I plasticizing agent. a costly source of heat for the production of steam is avoided. Wood softened by ammonia gas instead of steam is more pliable and can be worked into fairly intricate shapes, depending on the dimensions of the piece, without the use of clamps. Simple bracing or tying of a piece for little more than an hour is sufficient to give it permanently the desired shape and there is no problem of 'memory' retention. The information that followsand theconstruction of the treatment setup were the result of a research program that was, in part. made possible by the support of Collaboration in Art, Science and Technology Inc.. under a grant from the New York State Council in the Arts, and of Syracuse University. Alternative methods for plasticizing wood have been investigated in the U.S.A. since the late 1950's. R. W. Davidson and W. G. Baumgardt have indicated the es of the ammonia process, citing in particular its ability to soften wood to the extent that it might be manipulated very much as damp leather [I] (Fig. I). The portable studio plant we used in this research is shown in Fig. 2. It consists of a 150 Ib (68 kg) liquid ammonia storage tank, a treatment chamber of steel (12 ft (3.7 m) long and 8 in. (20 cm) in diameter) (ammonia is corrosive and will attack brass, copper and aluminum), a vacuum pump and a 55 gal. (208 I.) water drum with a continuous water supply. Piping connects the three units through a series of check, safety and drain valves. Wood is placed in the treatment chamber, the pressure in it is reduced below atmospheric pressure and ammonia gas is introduced. Pres- * Artist and teacher, Faculty of Fine and Performing Arts, ** Sculptor living at 156 Mountain Rest Rd., New Paltz, -~ ~ .State University College, New Paltz, NY 12561. USA. NY 12561. U S A . (Received 4 Mar. 1976.) sure, temperature and residence time in the chamber can be chosen to process woods of different kinds and thickness. It was found that the most satisfactory pressure is about 150 psi (10.5 kg/cm2) at about 70°F (21°C) and, as a rule-of-thumb, 30 minutes of treatment is sufficient for about each 0.25 in. (6mm) thickness of wood. Tests showed that wood pieces could be left in the treatment chamber for longer periods of time without damage, although excessive exposure to ammonia gas can result in a collapse of the cellular structure of wood. A similar result is obtained in steam processing. In Fig. 3 is shown ii wood sculpture containing pieces of wood formed after treatment by the ammonia plasticizat ion process. Sculpture: the Ammonia Plasticization Process.for Bending Pieces of Wood 55 Fig. 3. Dennis Connors. Untitled, wood sculpture in which curved parts were made with the ammonia gas wood-bending process, 48 x 56 x 112cm, 1975. After a piece of wood is treated, the ammonia gas is released from the chamber into the drum through which water is circulated to dissolve the ammonia gas. No noxious ammonia fumes are released in the working area duringthe treatment...