Whilst the shafts of the stone columns of the south front porticos at Hammerwood are unfluted, their capitals are fluted and lightly decorated. These capitals, (but not the rest of the columns) together with the pair of bacchic plaques which frame the portico doorways are made of an especially durable stoneware called Coade Stone, named after Mrs Eleanor Coade who ran a factory in Lambeth manufacturing this material from around the mid- 18th century until a century later. The particular properties of this stoneware - its low rate of shrinkage during firing, its malleability and durability - made it an ideal material for the casting of architectural embellishment and other decorative motifs, such as vases and urns. At the base of the pediment of the east portico at Hammerwood there is a stamped inscription: 'Coade, Lambeth, 1792.'
The use of Coade Stone by many eminent Georgian architects (including Robert Adam, Sir William Chambers, James and Samuel Wyatt, Sir John Soane and John Nash) was widespread and has been thoroughly discussed by Alison Kelly in her book Mrs Coade's Stone (1990). In this book, Kelly quotes a contemporary description of the making of this material, taken from David Laing's Plans etc of Buildings Public and Private executed in various parts of England (1818):
'a material which, although composed of various ingredients, may be described as a species of terracotta. It combines in one mass pipe-clay, flint, sand, glass and stoneware, that has already passed through the furnace. These are ground to a very fine powder, and are mixed in the proper proportions, and the whole is well kneaded together by means of the addition of water. In this state it forms a kind of paste which has the ductility of the clay usually employed in modelling; it is now wrought into the form desired ... and when finished it is left to dry gradually. When thoroughly dessicated, the performance is placed in a kiln, where it undergoes an intense white heat; and being allowed to cool it is now complete.'
There are no records of Latrobe's or Sperling's correspondence with Mrs Coade, but the choice of the bacchic plaques for a hunting lodge would seem to have been a definite attempt (as in the use of the primitive columns of the porticos) to enhance the rustic spirit of the house. The two plaques, in the form of friezes, are copied from the Borghese Vase, which stood originally at the Villa Borghese in Rome (it is now at the Louvre in Paris). As Alison Kelly states, the vase was one of the most admired pieces of classical art in the 18th century and the Coade factory produced copies from its earliest years up to the later 1820s. The best known Coade stone Borghese Vase was the example made for George IV at Royal Lodge, Windsor, to the order of John Nash in 1825. The incorporation of the design of the Borghese Vase into a pair of frieze-plaques, designed for the exterior of a building, is (as far as we know) unique to Hammerwood.