The base of the hearth was dug in the form of a saucepan, and covered with an inert and porous material rich in calcium or magnesium such as shells, lime, or bone ash.
22.
The refining of methods during the Medieval and Post Medieval periods led to the invention of the cupel which resembles a small egg cup, made of ceramic or bone ash which was used to separate base metals from noble metals.
23.
However, even in the 18th century, people complained about adulteration in food : " The bread I eat in London is a deleterious paste, mixed up with chalk, alum and bone ashes, insipid to the taste and destructive to the constitution.
24.
Spodium has a long history of medical usage, mentioned by Hippocrates and, for example, in the " Medical Poem of Salerno " " . . . Who knows the cause why Spodium stancheth bleeding ? . . . " ( in this case spodium referring to oxen bone ashes ).
25.
Archaeological investigations as well as archaeometallurgical analysis and written texts from the Renaissance have demonstrated the existence of different materials for their manufacture; they could be made also with mixtures of bones and wood ashes, of poor quality, or moulded with a mixture of this kind in the bottom with an upper layer of bone ashes.
