Coade Stone

The Coade stone products

From 1769, Mrs Coade’s factory in Lambeth, South London produced a wide range of finely shaped sculptural, architectural and ornamental features in ‘Coade stone’. While this was not the first artificial stone, the formulation and manufacturing technique perfected by Mrs Coade ensured uniform shrinkage during drying and firing, thus avoiding cracking and distortion.

In the 1980s, scientific analysis revealed the ‘secret’ formula for Coade stone to be a mixture of approximately 70% ball clay, 10% crushed fired clay ('grog'), 5-10% quartz grains and ground soda-lime glass (see Freestone, 1991). Firing this material in a kiln for several days, reaching temperatures in excess of 1,100 degrees centigrade, produced a durable ceramic varying in colour from pale yellow, to cream, to pink, with a smooth stone-like surface that was virtually impermeable to water.

Although most pieces were intended to imitate fine-grained limestone, some were also painted to resemble bronze or wood. These were usually candelabras, chimneypieces and other items for interior decoration. However, there are also examples of outdoor painted Coade stone such as the King George III statue at Weymouth.

Eminent sculptors were employed to model works of exceptional quality, both large and small, which were used to make plaster moulds in which the Coade stone pieces were cast. These could be either commissioned as bespoke pieces or selected from a catalogue featuring over 700 items such as capitals, friezes, fascias, panels and tablets, medallions and patera (ornamental circular or oval bas-relief discs), coats of arms, architraves, rustication features, chimney tops and more, as well as vases, statues and fountains for gardens. Since these items could be reproduced many times from the same moulds, they were significantly cheaper than carvings in stone.

Coade stone quickly became popular with the most fashionable architects and designers of the day, and the factory held royal warrants to George III and George IV. Coade stone enabled architects like John Soane and James Wyatt to use a rich variety of classical ornament in their building designs that would have been unaffordable in natural stone. The landscape designer, Lancelot ‘Capability’ Brown also ordered Coade stone classical decorative features, such as bas reliefs and figures, for garden buildings for his clients. However, as the products were competitively priced, their use was not restricted solely to the houses of the wealthy.

Examples of Coade stone are found throughout England and beyond. There are hundreds of listed buildings with Coade stone architectural or decorative features such as keystones, friezes and mantlepieces, and many historic gardens contain Coade stone fountains, urns and statues. The National Trust Collections website showcases some of these products online.

Architectural features, such as keystones, were generally incorporated into the structure in the same way as stone masonry, being set into load-bearing walls with lime-based mortars and fixed with dowels or cramps if need be.

Deterioration and repair

Coade stone has proved to be remarkably durable. Nevertheless, like other types of terracotta, it is susceptible to weathering, particularly in exposed locations. Typical defects include disfiguring accumulations of dirt or paint, water ingress through open assembly joints, rusting iron cramps, failure of old or unsuitable repairs and deterioration of original paint finishes.

Depending on the nature, extent and severity of defects, repair techniques range from small-scale surface repairs using suitable mortars to casting replacement elements. Where more than one example of the same Coade stone piece exists, it may be possible to use the intact piece as a model to make a mould that can be used to cast a replacement element for the damaged piece.

Before commissioning the repair of Coade stone, you should always seek advice on the causes of deterioration and options for conservation from an experienced conservator.

Case study: the Coade stone druid in Priory Park, Chichester

Chichester’s much-loved druid was originally placed above a water supply in South Street in 1776 and relocated as a feature in the public park in 1873. The statue is not listed but Priory Park is part of the city’s conservation area.

In 2019, Chichester District Council commissioned Cliveden Conservation to restore and repair their druid. The conservators had experience of repairing two identical druids at National Trust properties.

The druid’s right arm was separated at the shoulder and broken in several places. The right hand, which grasps an oak stave, was in poor condition. There was also some surface damage, and past repairs and previous painting had been carried out with unsuitable materials.

The statue was cleaned using a hand-held steam cleaner and non-caustic paint softener to remove loose paint and surface accretions. The conservators then refixed the broken elements using stainless steel microdowels and epoxy resin. A bespoke internal stainless steel armature was designed to strengthen the statue’s arm. ‘Coade’ pieces were made to repair surface damage. As in the original Coade stone process, modelling these repair pieces had to allow for shrinkage during the drying and firing process. Smaller repairs were modelled in hydraulic lime mortar. Finally, the whole statue was treated with a water repellant to protect it against weathering before being reinstalled in Priory Park.

Case study: Covent Garden’s Coade stone pediment sculptures

The east pediment of the Market Building at Covent Garden is adorned with a Coade stone ‘Flora’ goddess and other sculptures designed by R W Sievier. Conservation of the sculptures included cleaning accumulated pollution and dirt from the surfaces with stiff brushes, and the removal of biological growth with a combination of steam and biocides. Open fractures and failing repairs were replaced and filled with matching lime mortars. Loose and detached elements, such as the goddess’ arm raising a halo of flowers, were dowelled with carbon fibre rods and fixed in place with resin. The final treatment was to protect the surface with a shelter coat that brought out the pinkish hue of the Coade stone.

Coade stone chest tombs

There are some notable Coade stone chest tombs. The tombs are typically set on large stone slabs. The mass of the panels were planned so that they could be fired together and create a consistent finish overall. As well as an inscription panel, there are often symbols, such as drapes and inverted torches, representing death and mourning. These decorations were modelled separately and applied to the panels. It is not clear whether the decorations were fixed before or after firing. Over time, such enrichments may become loose and fall off, but the fixing holes remain as evidence that they were once there.

As for other grave monuments, the first step in assessing the conservation need of a Coade stone chest tomb is to carry out a survey. Our one-page guide about carrying out a survey and our monument survey form provide a step-by-step briefing. The surveyor should note both the structural and surface condition of the monument, as well as any environmental factors that might be affecting it, and try to determine the causes of deterioration. Although it is possible to replace damaged pieces with replica Coade stone, this is likely to be expensive and may be unnecessary. In many cases, structural defects can be strengthened by pinning and surface damage can be repaired with lime mortars and grouts. You should seek advice from a specialist conservator.

Further technical conservation advice and references

For more information on the conservation of artificial stone and other types of terracotta, see Historic England’s Practical Building Conservaton: Earth, Brick and Terracotta.

Coade’s Artifical Stone Manufactory (1784) A descriptive catalogue of Coade's artificial stone manufactory at King's Arms stairs, narrow-wall, Lambeth: opposite White-hall stairs. With prices affixed. (Accessed: Nov 2021)

Freestone, I C, Bimson, M, and Tite, M S (1985) ‘The Constitution of Coade Stone’ in Kingery, W D (ed) Ancient Technology to Modern Science, pp. 293–304 Columbus: The American Ceramic Society, Inc

Freestone, Ian (1991) ‘Forgotten but not lost: the secret of Coade Stone’ Proceedings of the Geological Association, 102(2), pp. 135-38 (Accessed: Nov 2021)

Karran, Laura (2015) 'Coade, Blashfield or Doulton? The in situ identification of ceramic garden statuary and ornament from three eighteenth and nineteenth century manufacturers’ Journal of Cultural Heritage

Kelly, A (1996) ‘Coade Stone: its character and conservation’; in Teutonico, J-M (ed) Architectural Ceramics: Their History, Manufacture and Conservation: A Joint Symposium of English Heritage and the United Kingdom Institute for Conservation 22–25 September 1994 pp. 32–8 London: James & James

Kelly, Alison (1988) ‘Coade Stone in Georgian Gardens’, Garden History, 16, pp. 109-133

Kelly, Alison (1990) Mrs Coade’s Stone (includes a gazetteer) Upton-upon-Severn: The Self Publishing Association Ltd

Ponting, M (2003) ‘Investigation of Coade Stone fragments from West Dean College, Sussex’ Historic England Research Report/Centre for Archaeology Report 93/2003

Scott, Simon (2009) ‘Artificial Stone. A successful substitute for natural stone?’

Stanford, Caroline (2016) ‘Revisiting the Origins of Coade Stone’, The Georgian Group Journal, XXIV, pp.95 -116

Swan, Simon (2017) ‘Artificial Stone: 19th-century Cementitious Sculpture and Rockwork’ The Building Conservation Directory 2017, pp. 87-91