Why Important
What to look for
The following materials were used for decorating walls, ceilings, fireplaces and furniture:
- Stucco: ‘stucco’ being used for fine work and applied decoration. It is similar in composition to plaster but marble dust is added instead of sand and hair. However, in Scotland the terms ‘plaster’ and ‘stucco’ are synonymous.
- Composition, or compo’: a mixture of resin and size, pressed into boxwood moulds and, when hard, fixed in place by glue or panel pins.
- Gesso enrichment: in use since the Middle Ages, a mixture of whiting, linseed oil and animal glue or size, built up in several layers over an armature. It is particularly suitable for ‘rococo’ curls, e.g. for three-dimensional wall sconces and girondelles.
- Papier-méché and carton pierre: two other types of pressed ornament used for applied decoration from the 1780s and throughout the nineteenth century.
- Carved wood: also used for decoration.
The basic cornice shape is “water leaf” run in situ along a cornice rod with additional decoration planted in wet stucco modillion and patera (found in very formal Georgian rooms) OR egg and dart details (often found in formal Victorian rooms). The styles were formal and had specific names:
- ANTHEMION AND PALMETTE
- EGG AND DART
- LEAF AND DART
- ACANTHUS LEAF
- GUILLOCHE
- MODILLIONS AND PATERA
- BEAD AND REEL
- MODILLIONS
When to look
Close visual inspection is the only certain way to detect loss of key.
Plain plasterwork in itself requires no maintenance, except periodic decoration, but the wise owner or agent will watch for cracks, signs of movement and dampness, or for evidence of fungal attack or woodworm infestation in the supporting timbers.
How to fix
An intact piece of fallen plaster may be reinstated by removing all dust and rubble, running plaster of Paris on to the back of the section, then pressing it into position and holding it up with struts until it has set.
This repair is only suitable where the backing and the surrounding plasterwork is sound. After brushing away all loose material and wetting the existing plaster and backing, the crack should be fully and firmly filled with a quick-setting plaster such as plaster of Paris.
The removal of emulsion paint from decorative plasterwork is laborious and expensive and is best tackled using steam. Non-caustic paint removers should not be used in conjunction with steam.
If a non-caustic paint remover is used, a small area should be tested first, as paint removers can damage the lime in the plaster.
When repainting after repair/replacement distemper or water-based paints are preferred, because they can be easily washed off. Colours should be chosen carefully to suit the original design.
If decorative plaster has been lost, reinstatement will require knowledge and skill; there are craftsmen who are capable of undertaking such work.
Decorative plaster can be reproduced by taking an impression with plaster of Paris from the original shape, either in situ or in the workshop. Glass-fibre moulds are used when large numbers of identical sections with simple profiles are required.
Undercut enrichments, such as acanthus leaves or paterae, are usually removed for copying, but if this is impossible an impression, or a ‘squeeze’, may be taken with latex, which can be peeled away from the original.
Avoiding creating problems
Damaged decorative plaster should be repaired or replaced in the traditional manner; standard modern designs in plaster or fibreglass are unsuitable for historic buildings.
Decorative plaster should be painted as seldom as possible; successive coats of emulsion paint will eventually obscure detail.
Non-caustic paint removers should not be used in conjunction with steam.