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Coade stone was a type of 'artificial stone' first created by Mrs Eleanor Coade (Elinor Coade, 1733-1821), and sold commerically from 1769 to 1833. The building boom in London, at this time, led to a high demand for ornate features to decorate and adorn brick-built Georgian houses. The showrooms of Mrs Coade's Artificial Stone Company, in Westminster Bridge Road, provided a huge array of 'off the shelf' solutions for builders and architects, ranging from small keystones for over front doors to corner and window features and almost entire façades. The factory was in Lambeth, London, where the Royal Festival Hall now stands. The company initially did very well, boasting an illustrious list of customers such George III and quite a few members of the English nobility (Wendy Moonan remarks in the New York Times that Mrs. Coade sold to "a Debrett's full of English lords and Dukes."). Despite the presence of Coade stone at such prominent sites as Column], Buckingham Palace, Castle Howard, St. Paul's Cathedral, Brighton Palace, Captain Bligh’s Tomb (in the churchyard of St Mary's Lambeth), the Lion outside County Hall next to Westminster Bridge and the sculpural reliefs above the entrance to the Imperial War Museum, after the first Mrs. Coade's death in 1821, her daughter and relatives (who inherited the firm) apparently did not do as well. The firm went bankrupt in 1833.
The material
Coade Stone is a form of Stoneware (vitrified ceramic). Mrs Coade’s own name for her products was Lithodipyra, which was a word constructed from ancient Greek words, which she strung together, meaning stone/twice/fire (λιθος/δις/πυρα). Its colours varied between light grey to light yellow (or even beige), and its surface's finish is best described as having a matte finish.
The ease with which the product could be moulded to complex shapes made it ideal for large statues, sculptures and sculptural façades. Moulds were often kept for many years, for repeated use. One-offs were clearly much more expensive to produce, as they would have to carry the entire cost of creating the mould.
One of the more striking features of Coade is its incredible weathering resistance, which is better than that of most stone in the harsh London environment. Thus, examples of Coade stonework have survived very well; prominent examples listed above have survived without any apparent wear and tear even after 150 years.
As a material, Coade stone was replaced by the much cheaper Portland cement (an artificial material) and it appears that it was largely phased out by the 1840s.
The formula
The 'recipe' for Coade stone is, however, still in existence, contrary to popular belief and it can still be produced. It was not a chemically-produced artificial stone, like concrete. It was kiln-fired ceramic. The manufacture required special skills; it was the careful control and skill in kiln firing, over days, that ensured success. This skill is even more remarkable, when the potential variability of kiln temperatures in those times is considered. Mrs Coade's factory was the only really successful manufacturer.
The formula used was:
- 10% of grog (see below)
- 5-10% of crushed flint
- 5-10% fine sand (to reduce shrinkage)
- 10% crushed soda lime glass.
- 60-70% Ball Clay from Dorset & Devon.
The 'grog' which was used was made up of finely crushed pre-fired items such as 'wasters' (material that had already been fired once). This was also referred to as "fortified clay" which was then inserted (after kneading) into a kiln which would bake the clay at a temperature of 2012 degrees Fahrenheit for somewhere over four days.
Mrs Coade
Mrs Coade was a resident of Lyme Regis, Dorset, living in Belmont House in that town. The pavement (sidewalk) outside the museum is inlaid with decorative examples of Coade stone, in the shape of Ammonites, set within its surface. They have proved durable enough to have survived the wear of myriad footfalls, over the years. Belmont House appropriately carries examples of the work on its façade.
Note
- "A Couple of Dogs that Never Need Feeding, And Other Garden Gems", by Wendy Moonan; pg. B36 of the New York Times, 28 April 2006
See also
Stoneware
External links
"Coade stone"