Certain recipes can tell us a great deal about the cultural and sometimes the technological contexts within which they were compiled and disseminated. In his mid-sixteenth century Italian treatise, the Three Books of the Art of the Potter.., Cipriano Piccolpasso (1523-79) discussed and illustrated the technology and the manufacturing processes that were central to the making of tin-glazed earthenware pottery. Frequently described as having been produced between the years 1556 and 1558, though revised throughout his lifetime, and as an instruction manual, the manuscript was unpublished until the mid-nineteenth century. Today, it is considered the authentic voice of the sixteenth-century Italian potter. However, as I have discussed elsewhere, Piccolpasso’s descriptions are based on observation of the techniques and processes employed by the potters of Castel Durante, rather than practice. Nevertheless his treatise is consistently and frequently cited in highly technical physical and chemical analyses of Renaissance glaze and related technology. The recipes discussed include those for colour as well as those for ‘ruby’ and ‘gold’ lustres: that is the addition of pristine metallic surfaces to otherwise finished ware. Piccolpasso says of them: ‘…I do not intend to go on further until I have discoursed to you upon gold maiolica, from what I have heard of it from others, not that I have ever made it or even seen it being done. I do know that it is painted over finished wares…’
While Piccolpasso is passing on hearsay, he nevertheless includes a recipe for what he calls Rosso da Maiolica [red maiolica]:
Red earth oz 3 6
Armenian Bole oz 1 0
Ferretto of Spain oz 2 3
Cinnabar oz 0 3
to which he adds: ‘…with this last mixture ‘B’, include a calcined silver carlino [a burnt coin]’. In his marginal notes he confirms that ‘…this last mixture “B” is called golden maiolica’.
The inclusion of particularly cinnabar is at first a mystery; it has no function in a recipe such as this. It is only when we know that cinnabar is a compound of mercury and sulphur and that all the ingredients are ground together in a pot of red [i.e. strong] vinegar, one of the ‘sharp waters’ employed by alchemists, that things begin to make a little more sense. During the period, what were described as the ‘arts of fire’, which included the making of pottery, were also used to make not only high status bronze-cast sculpture and gold-cast jewellery, for example, but also to manufacture and prepare more ubiquitous substances such as pigments and other colouring agents for an array of manufacturing techniques. These included easel and fresco painting, tesserae for mosaics, fabric dyes and the decoration of glass and indeed pottery. As has been observed, alchemy, in terms of practical chemistry, was primarily concerned with the making of industrial products by using chemical processes; it was not necessarily concerned with the occult, the mystical or the spiritual.
What Piccolpasso described was and is still known as a ‘transmutation lustre’ [my emphasis] in which a paste based upon raw clay is applied to the surface of a pot. It is a well-known technique: the fifteenth-century Hispano-Moresque potters used a red ochre clay corresponding exactly to that included in this recipe. A silver salt was added, in the form of a calcined carlino, together with a copper compound, known as Ferretto of Spain, to produce ‘gold’ lustre. No gold was ever used and in that sense it is the perception of gold that becomes significant.
The transmutation of base material into gold, however, was central to one of the alchemists’ most important aims, and mercury, sulphur and ‘sharp water’ were all part of the process. In his discussion of this recipe, Piccolpasso may well have been relying on what he knew of the presence of alchemy in all kinds of chemical and physical practice, including the production of gold maiolica. More specifically, he raises the question: to what extent might the potters of north-central Italy, in employing their own art of fire, be considered alchemists? What is more certain is that the philosophy associated with alchemy provides an insight into the ways in which knowledge and what kinds of knowledge were gathered and transmitted during the period. Ultimately, Piccolpasso’s record of what he understood as the recipe for ‘gold’ lustre reflected the endeavours of contemporary scholars and indeed pottery practitioners to cope with the challenges of defining and connecting all the different kinds and parts of knowledge that were circulating at that time.
 Piccolpasso, Cipriano, Li tre libri dell’arte del vasaio nei quai si tratta non solo la pratica, ma brevemente tutti gli secreti di essa cosa che persino al dè d’oggi è stata sempre tenuta ascosta…ecc., National Art Library, Victoria and Albert Museum, South Kensington, London, MSL/1861/7446
 Caiani, A., 1857, I Tre Libri dell’Arte del Vasajo, Roma, dallo Stabilimento Tipografico, Via del Corso, num. 387.
 See, for example, G. Padeletti, G. M. Ingo et al, ‘First-time Observation of Maestro Giorgio Masterpieces by Means of non-destructive Techniques’, Applied Physics. A, Materials Science & Processing, 0947-8396, Padeletti, 2006, vol. 83 issue, 4, pp. 475-483; B. Brunetti et al., ‘Copper in Glazes of Renaissance Luster Pottery: Nanoparticles, Ions and Local Environment’, Journal of Applied Physics, 93/12, 2003, pp. 10058–63
 A. Y. Al-Hassan, Studies in al-Kimya’, 2009, p. 8; see also L. Abraham, A Dictionary of Alchemical Imagery, 1998, p. 11.