230 BOOK VII. 



good, for the cupels made from them, since they are not sufficiently dry, 

 frequently crack and break in the fire and absorb the metals. If ashes of 

 beech or similar wood are not to be had, the assayer makes little balls of such 

 ashes as he can get, after they have been cleared of impurities in the manner 

 before described, and puts them in a baker's or potter's oven to burn, and from 

 these the cupels are made, because the fire consumes whatever fat or damp 

 there may be. As to all kinds of ashes, the older they are the better, for it is 

 necessary that they should have the greatest possible dryness. For this 

 reason ashes obtained from burned bones, especially from the bones of the 

 heads of animals, are the most suitable for cupels, as are also those ashes 

 obtained from the horns of deer and the spines of fishes. Lastly, some take the 

 ashes which are obtained from burnt scrapings of leather, when the tanners 

 scrape the hides to clear them from hair. Some prefer to use compounds, 

 that one being recommended which has one and a half parts of ashes from the 

 bones of animals or the spines of fishes, and one part of beech ashes, and half a 

 part of ashes of burnt hide scrapings. From this mixture good cupels are 

 made, though far better ones are obtained from equal portions of ashes of 

 burnt hide scrapings, ashes of the bones of heads of sheep and calves, and 

 ashes of deer horns. But the best of all are produced from deer horns alone, 

 burnt to powder ; this kind, by reason of its extreme dryness, absorbs metals 

 least of all. Assayers of our own day, however, generally make the 

 cupels from beech ashes. These ashes, after being prepared in the 

 manner just described, are first of all sprinkled with beer or water, to make 

 them stick together, and are then ground in a small mortar. They are ground 

 again after being mixed with the ashes obtained from the skulls of beasts or from 

 the spines of fishes ; the more the ashes are ground the better they are. 

 Some rub bricks and sprinkle the dust so obtained, after sifting it, into the 

 beech ashes, for dust of this kind does not allow the hearth-lead to absorb 

 the gold or silver by eating away the cupels. Others, to guard against the 

 same thing, moisten the cupels with white of egg after they have been made, 

 and when they have been dried in the sun, again crush them ; especially if they 

 want to assay in it an ore or copper which contains iron. Some moisten the 

 ashes again and again with cow's milk, and dry them, and grind them in a 

 small mortar, and then mould the cupels. In the works in which silver 

 is separated from copper, they make cupels from two parts of the ashes of 

 the crucible of the cupellation furnace, for these ashes are very dry, and from 

 one part of bone-ash. Cupels which have been made in these ways also 

 need to be placed in the sun or in a furnace ; afterward, in whatever way 

 they have been made, they must be kept a long time in dry places, for the 

 older they are, the dryer and better they are. 



Not only potters, but also the assayers themselves, make scorifiers 

 and triangular crucibles. They make them out of fatty clay, which is 

 dry 5 , and neither hard nor soft. With this clay they mix the dust of old 

 broken crucibles, or of burnt and worn bricks ; then they knead with a 

 pestle the clay thus mixed with dust, and then dry it. As to these crucibles, 

 , "Dry." This term is used in centra-distinction to pingue, unctuous or "fatty." 



