Many of the "signs and tokens" described in alchemical texts relate to colour, from the Crow's Bill signifying putrefaction to the philosophical solvents disguised as Green Lions, Red Dragons, and Grey Wolves. While the process of yellowing, or citrination, often appears in medieval recipes, it seems to have interested commentators less than the more familiar processes of blackening, whitening, or reddening. Yet beyond these canonical colours, yellowness turns out to be ubiquitous in alchemy and its associated craft practices, both in Latin texts and vernacular translations. This paper uses source criticism and experimental reconstruction to interrogate the role of yellowness at the beginning, middle, and end of practice, focusing on fifteenth- and sixteenth-century England. As starting ingredients, yellow vitriol and litharge offered the potential for transmutation but also posed problems for identification and preparation. As an intermediate stage, yellowness offered promising signs of future success, in the form of dramatic colour changes and unexpected products. But yellowness also offered an end in itself, as appears from the many citrination processes attested in recipe collections which aimed to imitate the properties of gold - suggesting that yellowing was prized as a significant indicator of chemical change across diverse areas of craft practice.
Nitric acid became commonly available in the seventeenth century. Since then, it held the interest of chemists, especially those interested in the art of dyeing. Due to what is now called the xanthoproteic reaction (from Greek xanthós, describing shades of yellow), nitric acid produces a stable yellow colouration in proteinaceous materials, such as wool, silk, and bones. The chemistry of this reaction is well understood today. Less well-known is that it held the interest of dyers in the past. Dyers considered the ability of nitric acid to give a yellow colour to certain substances a solution to giving materials a durable, that is, a lasting, yellow colour. Yellow, indeed, posed a problem in the art of dyeing. Before the discovery of synthetic dyes in the mid-nineteenth century, there were no organic yellow dyes with long-term colour stability. Using historical dyeing manuals and chemistry treatises, combined with our practical engagement with the processes they describe, this paper traces how, between the seventeenth and nineteenth centuries, dyers explored nitric acid while examining the durability of yellow colourations. Based on these explorations into nitric acid, the chemical arts developed theories about the nature of colour, and about the causes for its relative permanence.
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：