While fibrous plaster methods have continued to be used for ornamental work right up to the present day, the twentieth century has seen the introduction for plain work of a wide variety of proprietary plasters, designed to save labour, time and money, and a trend towards ‘dry lining’, resulting in the virtual elimination of the plastering trade altogether. In the process, the traditional techniques associated with lime plaster, stucco and clay have been largely forgotten and it has become common for decayed or damaged plaster of all ages and types to be repaired using inappropriate materials and methods for ornamental work of all sorts to be ‘restored’ by fibrous plaster techniques, the surviving original fabric being destroyed and reproduced in the process.

The value of historic plaster-work depends not only on its design, but also — as with a picture or a piece of furniture— on the authenticity of its fabric and the qualities which ageing has introduced. In an architectural context, the reproduction of plasterwork which is important to the overall design, but missing, may well be justified. But good conservation practice requires that, wherever possible, surviving original work should be retained and repaired and, where necessary and appropriate, restored.

This Technical Advice Note contains an account of the types of plasterwork which may be encountered; guidance on how to inspect plaster-work, to assess it, to diagnose defects and devise a conservation strategy; and advice on repair and restoration methods and their specification. It does not purport to be a handbook for the trade, for which a number of practical references are given in the bibliography. Matters of style and design are also beyond its scope. Current advice on architects, craftsmen, conservators, and sources of materials may be obtained from the Historic Scotland Conservation Bureau.

Wide consultation with architects, conservators, plasterers and other specialists working with historic buildings has taken place in the preparation of this paper. Attempts have been made to take all views into account without necessarily committing them all to print. There has not always been full agreement between consultants — most notably on the extent to which lime plasters may traditionally have been gauged with gypsum. There is still much to be learned from documentary and archaeological evidence and from practical experience. Further comment is welcomed and where appropriate any future edition may be amended accordingly.