Dictionarium polygraphicum. To make glass of a sapphire colour.

Dictionarium Polygraphicum:
Or, The Whole Body of Arts Regularly Digested.
Vol II.
London: Printed for C. Hitch and C. Davis in Pater-noster Row, and S. Austen in St. Paul's Church Yard. MDCCXXXV.
1735
To imitate the colour of sapphire in glass, which is of a clear and transparent blue, you must put to half an hundred pound of frit of rochetta, half a pound of zaffer prepar'd, with half an ounce of manganese of Piedmont, also prepared, as we have shewn: well mix these powders with the frit, then put the whole into a pot in a furnace, letting the glass be well melted and purified 1 for the longer it remains on the fire, it becomes so much the finer, if you rake care to take it out from time to time. Then mix it very well, and make an essay of the colour; and if it be not full enough, augment or diminish it as much a* ou think sit; then the glass may be wrought, and you will ave a sapphire of the colour of the double violet of Consiantinople, which the small dose of manganese produces.

To give glass a finer sapphire colour.
Glass will have a much fairer sapphire colour, if in the room of frit of rochetta, you take good crystal frit, and add to it die same dose of powder, as in the preceding snicle. Of this glass thus tinged, you may make what woiks you please. You must not put the powder of manganese and zaffer on the melted glass, but mix it with the frit, as we have noted: for the colour the melted glass takes, is not so sine, as when the materials are first mixed.

To make a paste for sapphire colour.
The sapphire is very much esteemed for its beauty, which is a very clear sky-colour, and pleasant to behold. There are some whitish, like diamonds, others very blue, and some violet colour; the stone is soft, bat easy to harden.
To make this paste, take two ounces of natural crystal prepar'd, four ounces and a half of minium, twenty-six grains of the blue smalts the painters use: the whole being well-pulverized, put them in a crucible, and cover and lute it well; then put them in the furnace to bake, as long time as before prescribed 1 and you'll have a fine violet colour approaching blue.

Another oriental sapphire.
The paste for this sapphire will be nearer oriental than the former; take two ounces of natural crystal prepar'd, six ounces of minium, to which add two scruples of zaffer prepared, and fix grains of manganese also prepared; the whole reduced to a fine powder: mix them well together, and put them in a crucible, and cover, and lute it well; then put them in the furnace to bake, the same space of time as before shewn, and you'll have an oriental sapphire of a very fine violet colour.

To make a deeper oriental sapphire.
This paste for sapphire will be of a deeper colour than the for mer, you must put in two ounces of crystal prepared, five ounces ofminium, forty-two grains of prepared zaffer, and eight grains of manganese of Piedmont also prepared; the whole reduced to an impalpable powder, and mixed well together. Moreover proceed, observing well all circumstances, and you'll have a sapphire deeper than the preceding, somewhat tending to a violet colour, which you may work, polish, and set.

Another very fine blue sapphire.
The blue colour of sapphire is no less agreeable than the violer, and it is the male of its kind. To mate it, take one ounce of crystal in powder, add to it a drachm of salt of vitriol, three grains of verdigrease, one grain of azure; an ounce, one drachm and four grains of fine silt of tartar; the whole in fine powder: put it into a crucible, covered and luted, to be baked and purified, as we have heretofore shewn, and you'll have a very fine blue sapphire, &c.

Another fine sapphire.
The colours of these sapphires being different, by the dose and mixture of the ingredients, we will slievv each in a chapter by itself. Take two ounces of powder of crystal, two ounces of fine silt of tartar, five drachms twenty-four grains of verdtgreaje, and thirty-two grains of azure; the whole reduced to im palpable powder, which you must set to bake and purify in a covered crucible in a glass-house furnace, as we have said before, and youH have a very fine sapphire. The way to make a violet sapphire. We shall shew several ways of making sapphires of our crystal of different colours.
To make this, take one ounce of powder of crystal, one drachm of salt of vitriol, and nine drachms of fine salt of tartar, the whole in fine powder; then proceed fur ther, as we have shewn in the preceding chapter, and you'll have a sapphire of a very fine violet colour.

To make an oriental sapphire.
To imitate this precious stone with the matter prepared with saturnus glorisicatus and natural crystal, take ten ounces; add to them two drachms of the cabc of gold, (see the calcination of GOLD;) mix these powders well together, and put them into a crucible covered with another: let them dry, and then sec them in a glass-house furnace for three days, and do all that is directed as to the oriental ruby; and that mass will be a very fair oriental sapphire, which cut and polish at the wheel.