Modern Organic Materials Meeting

Art/Science Forum Edited by Susannah Gardiner Modern Organic Materials Meeting by Clare Meredith Conservators, curators and scientists responsible for the care of twentiethcentury collections are constantly confronted with materials whose structure, behaviour and degradation systems are unfamiliar. On 14 and 15 April 1988,the Scottish Societyfor Conservation and Restoration (S.S.C.R.) organised the first meeting to address itself to these problems. The 2day Modern Organic Materials Meeting in Edinburgh attracted delegates from museums in Britain and abroad responsible for a variety of artefacts: contemporary sculpture, textiles, film archives, modern furniture, paintings, industrial artefacts and objets d’art. The participants included curators,collectors and conservation scientists, but most were conservators. This balance was reflected in the speakers’ programme, with the addition of representatives from industry and appropriate university research departments. The papers, published as preprints by S.S.C.R., fell into three broad categories. The first included basic information about polymers, their degradation and the development of the modern industry. A second, smaller section included information on both high- and low-technology methods of identification in current use. The remaining papers presented interesting case histories on a variety of objects and materials. Despite the title of the meeting and the broad cross section of professional disciplines of those who attended it, the emphasis was on plastics and rubber. This is reflected in the topics of many of the papers given, which included the ClareMeredith,S.S.C.R.,c/o ConservationStudio, HopetounHouse,SouthQueensferry,West Lothian EH30 9SL, U.K. Received 5 May 1988. following: an introduction to polymer chemistry relevant to plastic collections; the degradation of polymeric materials; the history of industrial research and development inpolymers;simplemethods of identifying plastics; the identification of modern polymer systemsusing Fourier transform infrared spectroscopy;cellulose acetate deterioration in the sculptures of Naum Gabo; an investigation into the deterioration and stabilisation of nitrocellulosein museum collections;theeffect of solvents on four plastics found in museum collections; practical answers to plastic problems; the treatment of social history objects made of natural rubber; and the deteriorationand preservation of rubber in museums. The sculptures by Naum Gab0 in the Tate Gallery, London, were discussed and the problem plastics identified as cellulose acetate rather than cellulose nitrate. Preventative conservation measures were reviewed. Cellulose acetate is used as the base for modern cinema films and widely used for archival copying of deteriorating films of nitrate stock. Cellulose acetate has now proved unstable and breaks down to release acetic acid and plasticiser. Tests are in hand to identify and to introduce possible stabilisers into the polymer. Fourier transform infrared (FTIR) spectroscopy has been used for 3years at the Victoria and Albert Museum in London. Infrared radiation is not split into its component wavelengths but an interferometric technique is employed, and the radiation is subsequently translated into a normalspectrum by a Fourier transform. The characteristic spectra confirm analysis of materials, although multi-component polymer systems produce a complex infrared spectrum. A practical approach to plastics conservation waspresented, with an emphasis on adhesives and inpainting. The speaker discussedthe effectsof solventsonplastics and gave tables of the solubility parameters of plastics and solvents and a listing of plastic susceptibilities. A presentation ontheconservation of a pair of 1920srubber bathing shoes raised several questions concerning storage and display (the solution here was to use a nitrogen-filled case, which is not always practicable); time-consuming research and innovative treatment; and the ethical issues raised by reshaping the objects. Another speaker discussedproblems in the assessment of the degradation of polymeric materials and reviewed the mechanisms by which molecular size is changed by either fission or formation of chemical bonds. Moisture, heat, light and oxygen are the principal sources of chemical reactions, and stress can have a major influence on the rates of change and the early recognition of degradation. It is infrequent that degradation arises as a result of a single mechanism. The meetingproved to be an important review of current understanding in these areas and an indication of the scale of problems in the hands of those caring for twentieth-centurycollections.Satisfactory storage and environmental conditions would seem a prerequisite, but they must be accompanied by an understanding of the complexity of the materials from...