Dictionarium Polygraphicum. ÆS USTUM, to make.

Dictionarium Polygraphicum:
Or, The Whole Body of Arts Regularly Digested.
Vol I.
London: Printed for C. Hitch and C. Davis in Pater-noster Row, and S. Austen in St. Paul's Church Yard. MDCCXXXV.
1735Take bits or thin leaves of cop per fifteen ounces, sulphur in powder ten ounces, sea salt finely powdered fifteen ounces, fill the crucible by laying in layer upon layer; put it into a furnace of live coals, and let it stand till the sulphur is wholly consum’d; then take it out, and it will be of an iron grey, but reddish within; it gives a noble fine tincture to glass.

Another Æs Ustum. Take thin plates of the reddest copper (i. e. the rose copper) make it red hot, and extinguish it in urine, in which common salt has been dissolv'd: reiterate this operation till it becomes of the colour of gold, both with in and without; after which cement those places with this powder. Or

Take sulphur two pound, salt petre two pound, vitriol calcin'd to redness one pound, reduce all to a powder, put the plates with the powder into a crucible layer upon layer, cover it with another crucible having a whole in the bottom, lute them together, and being dry, put them into a circulatory fire (having hot embers underneath) for six hours: for the first two hours let the fire be a foot distant from the crucible, the second two hours let it be half a foot from the crucible, and the last two hours let it be close to the crucible, cover it.

Take care that the fire be not too violent, that the matter may not melt, for if it does it is spoil’d. When it is cold reduce it to a fine powder, wash it, dry it, and keep it for use.

There are other curious persons who make an Æs ustum, yet finer than this, and more penetrating in colours; but the preparation is more costly and requires more time; for instead of brimstone and salt-petre, they make use of a purified sulphur, and fix’d with sal-armoniac; and instead of ordinary red vitriol they use Roman vitriol, which they prepare with the lee of urine, and a fusil salt; which they afterwards put into a reverberatory. Dictionarium Polygraphicum. Containing. Polygraphick Dictionary. ÆS USTUM, to make.