G L A S S. 



fufioti twelve hourj moiT, it will be fit to work. It is very 

 tC'.ider aiiJ brittle, and muil be woikcd with great can-, 

 taking it llowly out oi' the pot, and. continually wetting the 

 njai-ble it i.s wrought upon. Neri. 



It is well known, that cerufs, or white lead, minium, li- 

 tharge, and all t!ie otlier preparation;! ar.d calces of lead, 

 arc eafily fufed by a moderate fire, and formed into a tranf- 

 parent glals of a deep yellow colour. • BuL tills glafs is fo 

 penetrating and powerful a flux, that it is ilccefi'ary to give 

 it a greater confillcn-;e, in order to rerder it fit for ufc. 

 With this view, two paiis of calx of L-ad, f._f. minium, 

 and other parts of land, or powdered flints, may be put 

 into a crucible of relraclory clay, and baked into a compact 

 body. Let this crucible, well doled wiih a luted lid, be 

 placed in a melting furnace, and gradually licated, for an 

 hour, or an hour and a half; and aflcrwards-let the heat be 

 increafed, fo as to obtain a complete fulion, and continued 

 in^that ftate for the fame time: let this crucible n.main to 

 cool in the furnace, and when it is broken, a very tranfpa- 

 vent yellow-coloured glals will be found in it. iSom.e add 

 nitre and common fait to the above mixture, becaufe thefe 

 lalts promote the fufion and the more equal diilriljution of 

 the fand. This glals of lead has a confiderable fpecific gra- 

 vity, and its lowell part is always the heaviell. It is an im- 

 portant flux in the affays of ores to facilitate their fcoriiica- 

 tions. 



Glafs of lead is capable of all the colours of the gems in 

 very great perfection. The methods of giving them are 

 tthefe: for green, take polverine frit twenty pounds, lead 

 calcined fixtcen pounds; fift both the powders very fine; 

 then melt them into a gkifs, feparating the unmixed lead, 

 by plynging the mals in water; after this return it into the 

 pot, and add brafs thrice calcined fix ounces, and one penny' 

 weight of crocus martis made with vinegar; put this in at 

 fix different times, always carefully mixing it together; let 

 it finally fettle an hour, then mix it together, and take a 

 proof of it; when t!ie colour is right, let it Hand eight 

 hours, and then work it. If inflead of the calcined brafs 

 the fame quantity of the caput mortuum of the vitriolum 

 veneris be ufed, the green is yet much finer. 



For topaze-colour take cryflal frit fifteen pounds, cal- 

 cined lead twelve pounds; mix them well together, by fift- 

 ing the pov.dcrs through a fine fieve ; then fet them in a 

 furnace not too hot, and feparate the fuperfluous unmixed 

 lead, by calling the whole into water: repeat this twice; 

 then add half gold yellow glafs, and let them incorporate 

 «Hd purify, and they will be of the true and exatt colour of 

 the original topazes. 



For fea-green, take cryflal frit fixtcen pounds, calcined 

 lead ten pounds; mis and fift them together, and fet them 

 in a pot in a furnace: in twelve hours the whole will be 

 melted; then caft it into water and feparate it from the 

 loofe lead; put them into the furnace agam for eight hours; 

 then feparate the loofe lead by waOiing a fecond time, and 

 return it to the pot for eight hours more. Neri. See Gems. 

 Glass, Painting in. The primitive manner of painting in 

 g'afs was very fimple, and of confequence very eafy : it con- 

 iilled in tlie mere arrangement of pieces of glafs of different 

 colours, in fome fort of fymmetry ; and conilituted a kind 

 of what we call Mofak ivork. 



Afterwards, when they came to attempt more regular de- 

 figns, and even to reprefent figures raifed with all their 

 fliades, their whole addrefs went no farther than to the draw- 

 ing the contours of the figures in black, with water colours, 

 and hatching the draperies, after the fame planner, on glafl'es 

 of the colour of the objeft intended to be painted. For the 

 carnations, they thcfe glafs of a bright red; upon which 



thev (Jefigncd the principal lineaments of the face, S:c. wltk 

 black. . 



At lafl the taflc for this fort of painting being confider- 

 ably improved, and the art being found applicable to the 

 adorning of churches, bafilicas, &c. they foiuid means of 

 incorporating the colours with the glafs itfelf, by expofing 

 them to a proper degree of fire, after the colours had been 

 laid on. ^ 



A French painter at Marfeilles is faid to have given the 

 firlt notion hereof, upon going to Rome, under the pontifi- 

 cate of Julius II. But AlbffTt Durer, and Lucas of Ley- 

 don, were the firit that carried it to any height. 



The colours ufed in painting on glafs are vei-y different 

 from thofe ufed either in painting in od, or water. 



The black is made of two-thirds of flakes, or fcalcs of 

 iron, beaten up, and mixed with another third of rocaille, 

 or little glafs beads, li'hite, with fand, or little wh.ite peb-- 

 blcs, calcined, pounded in a mortar, and afterwards ground 

 on marble ; with one fourth-part of falt-petre, added there- 

 to, and the mixture calcined and pulverized over again: to 

 which, when they arc ready to ule it, is added a little gyp- 

 fum, or plafter of Paris well ground, &c. For yellow, 

 they ufe leaf-filver ground, mixed up in a crucible, with^ 

 fulphur or falt-petre; then well beaten and g-iound on a 

 porphyry ftone; and, at length, ground over again with 

 nine times as much red ochre. Red is made of litharge of 

 filver, and fcales of iron, gum Arabic, ferretta, glafs-beads, 

 and blood-ftone, nearly in equal quantities. This is one of 

 the moll difficult colours, and the preparation only to be 

 learned by experience. Green is made of it% uftum, one 

 ounce; as much black lead, and four ounces of white fand, 

 incorporated by the fire. After calcination, they add a 

 fourth part of falt-petre : after a fecond calcination, a fixth 

 part more : after which they make a third coftion before it 

 is ufed. A'^ure, purple, and 'violets, are prepared like green, 

 only leaving out the a;s ullum, and in the lieu thereof ufing 

 fulphur for azure; perigueux for purple; and both thefe 

 drugs for violet. Carnations are made of ferretta and ro- 

 caille. And laftly, colours for the hair, trunks of trees, &c. 

 are made of ferretta, rocaille, &c. 



This account of colours we have from M. Felibien's ex- 

 cellent work Des Principes d'Architcfture, &c. though it 

 muft be owned, that all the painters an glafs do not ufe 

 then- ; there being few artifls of that kind but have in- 

 vented their own particular ones, whereof they ufually 

 make great fecrets. But this is certain, that thefe above 

 •defcribed are fufficient for the bcfl paintings of all forts j 

 provided the perfon has but the flcill to manage them. 



In the windows of divers ancient cluirchea, chapels, col- 

 leges, &c. we meet with the mofl beautiful and lively 

 colours imaginable ; fuch as far exceed any ufed among 

 \is : but it is not tliat the fecret of making thofe colours 

 is loll ; but that tlie moderns would not go to the ex- 

 pence of them_; nor take all the neceffary pains ; becaufe 

 this fort of painting is not now fo much eftcemed at 

 formerly. 



Mr. Walpole, in his Anecdotes of painting in England, 

 has traced the hillory of this art from the reformation, 

 wlien mifguided zeal deilrov»d moll of the monuments 

 of it in our chiu-clies, through a feries of protefTors to the 

 prefent time. Among the later proficients in this art 

 were Ifaac Oliver, who painted the windows at Chrift- 

 church, Oxford, in 1 700 ; William Price, who in the 

 fame year painted the windows in Merton chapel ; William 

 Price, the ion, to whofe art we owe tlie wii.dows at 

 yueen's. New-college, and -Maudlin, of whojn Mr. 

 W^alpole fays, that liis colours are fine, liis drawing 

 4 goo<l> 



