The art of glass shewing how to make all sorts of glass, crystal and enamel : likewise the making of pearls, precious stones, china and looking-glasses : to which is added, the method of painting on glass and enameling : also how to extract the colours from minerals, metals, herbs and flowers ... : illustrated with proper sculptures / written originally in French, by Mr. H. Blancourt, and now first translated into English ; with an appendix, containing exact instructions for making glass-eyes of all colours.

CHAP. CCLI. The Way to make Looking-glass.

ALL those who employ themselves in the Art o•• Glass, do it always without derogating from their Quality, as we have noted in Chap. 3. which our Kings have always taken care to maintain.

The Undertakers of the Royal Glass-Manufacture in France, when they obtained their Grants of Pri∣viledges, did at the same time require, That al•• Persons of Quality, who should associate in the Ma∣nufacture, might do it without lessening their Quali∣ty; to which his Majesty agreed with Exemptio•• from their Taille, and several other Privileges, a•• Quartering of Soldiers, &c. for all such, their Sub∣stitutes, Servants, and Domesticks.

The first Grant of Priviledges to this Manufa∣cture, bears Date in October 1665. in Favour of Nicholas du Noyer, for Twenty Years, which was renewed by Letters Patent of the last of December 1683. for Thirty Years to Peter Bagneux.

The second Privilege for the Manufacture Royal of Large Glass, was granted Decemb. 14.1688. to Abraham T' Hevart, for Thirty Years, with the saving Pri∣vilege of Nobility as the former: These having set∣led at St. Gobin, near La Fere, did by Letters Patent of February 1693. obtain Exemption from the Tailles, (or Subsidy on the Third Estate, which is a constant Tax) and other Impositions, as well for themselves, as their Deputies and Servants.

And to avoid all Contest, these two Manufactures were united by Order of the Council of State, April 19. 1695. and Confirmed May 1. following, under the Name of Francis Plaistrier.

Now for making these Glasses, the same Crystal assigned throughout Book 1. is sufficient; the Dif∣ference is only instead of Working it as you do there, to cast it flat and not blow, as in Chap. 3. to which we refer the Reader.

The Manner of Casting the Metal, did not com∣mence with the Invention of Looking-glass; for the Workmen at first, used to take a piece of Metal ve∣ry large, clipt and done on the Marble into Quarries as big as they'd have them; these they set after∣wards on a Pallet of Iron in the Furnace, till they were in a Fusion, and so spread and united; hence they took and put them into another little Furnace for that purpose, S. S. S. with fine searced Ashes to Bake; this done, they raised the Fire by degrees, and so let it go out again, and drew off the Glasses, working them after our manner in the next Chap∣ter.

Thus too they wrought their little Round Glasses, or Mirrours, first shaping them out of a long piece of Metal, by Circumvolution, and afterwards clip∣ping them as the former, so finished them in the Furnaces, and made them fit for Polishing.

Since that time having attempted to make them very large, they fell upon the Way of Casting the Glass like other Metal on Sand Beds, such as the Founders use; and to perform it the better, they have a Roller of Metal to run over the Surface of the Glass Metal for enlarging the Plate, and to smooth and compact it withal.

For such as would make them very large indeed, as are wrought at Muran near Venice, and in our Royal Manufacturers, they had a much better, and easier Method than doing them on Sand, viz. in large Tables of well polished Copper, whereon they cast the Metal, but these not having strength enough to abide the Heat, we have since made use of Iron, which will sufficiently perform the Effect.

These Tables whereon the Glasses are at first sight Cast to their proper Largeness, must have their bottom sunk as low as you intend the Thickness of your Glass-Plate, and have a Conveniency to push it out, as soon as ever 'tis prepared thereon.

Some make use of Marble ones with Covers, o∣ver which they have a Plate, or Runner of Metal, to slide and press it on the Glass Metal, that the Glass Plate may be the more compact and even.

Thus are large Glasses made, which are no less surprizing than pretty, and 'tis a very considerable Improvement they are brought to at this Day, of making them so extraordinary large for Mirrours: One would admire to what Perfection the Wit of Man may arrive at, and is capable of bearing from the advantage of Serious Application and Study in profound Matters.