Historically plastering in Britain was carried out mostly using lime based plasters. Lime was used as a binder to be mixed with various types of graded sand used as an aggregate to suit the backgrounds to which they were to be applied, achieving the required finish. However White Chapel art Plaster Co, regularly work on Commercial projects restoring buildings which can include 500 plus square metres of 3 coat lime plaster to restore back to the original work.

When plastering internal walls or buildings, especially where the base coats were applied onto timber laths, horse hair to goats hair was added to the mix to reduce cracking as today’s plasterers use scrim.

The sand used in these mixes was usually a fairly coarse well graded plastering sand for the backing coats in a ratio of between 2 to 3 parts sand to one part lime. For finishing coats the sand used would be a very fine silver sand or similar, with the sand content greatly reduced and the lime content increased.

Lime mortars were also used for external rendering and lime was also mixed with natural pigments to produce lime wash to be used as a decorative finish on lime plastered walls.

Lime plaster run in situ cornice was the traditional way of forming mouldings on ceiling to wall joints.

Lime plasters are highly compatible and well suited to traditional buildings allowing the building to breathe and are more forgiving than cement based renders if slight movement of the building occurs.

Fine hairline cracks can be self healing from free lime present in good quality sand lime mixes.

In summary, there is much to be gained by using lime plasters in traditional buildings, so why did they ever fall out of favour?

The mixing and application of lime plaster is a highly skilled and slow process with many different mixes required for differing situations. Time taken for lime plaster mixes to go off is lengthy and preventing cracking of finished lime plaster during the drying period is difficult.

Modern gypsum pre-mixed plasters are easy to mix, move and apply and are safer to use for the craftsman applying the materials.

Where dampness is not an issue in buildings using gypsum based pre-mixed plastering materials is a quicker and cheaper way to obtain excellent results.

Through gypsum plasters are considered to be a modern innovation, gypsum was in fact used by the ancient Egyptians. It has been used for casting individual plaster ornaments for centuries and in fibrous plastering for the last 200 years.

In reality plasterers of yesteryear would usually gauge finishing setting coats with retarded gypsum to obtain a quicker set and reduce cracking.