S E C T 1 O N IV.
Of the manner of laying the colours on
glafs grounds,and burying them.
. . . • - • - ' *.
THE fame affinity betwixt painting in
eaaifiel and on glafs by burning, which
renders, the preparation of the colours fo much
the fame inboth,..extends itfelf: alfo to the
manner of faying the colours on the grounds,
and burning mem.
The manner of tempering the colours and painting with them on glafs, may therefore be exactly the fame as was before directed for enamel j the oils of fpike or lavender, and of turpentine, being alike fuitable in this cafe as in the other: but with refpedt to die manner of burning the colours, though the general methods, muff: be the fame, yet a variation in certain particulars is in iome cafes neceflary: whiph I fhall therefore take notice of here.
Smaller plates, or other figured;bodies of glafs, may have -the colours burnt in the fixt or loofe muffles j but larger plates require coffins, which may be formed in the fame manner as was directed for enamel, though, as the form of the plates in this cafe are flat, and not convex, as is neceflary in the other, a number of layers or ftrata may be put into the fame coffin: for it is not material how near the fur- faces of the plates are to each other, provided
they do nottquch,. The bell method of plac-; iag. theip to advantage in the coffins, is to. have iron plates adapted to the qpffins ; which: icon plates fhould have at every corner a fmall hit of iron going off at right angles* ;ffiat the. plates being put over e^teh other may be fup-: ported by tnefe bits of irons as |hprt pillars}., and kept at fuch diftance from each other, as! will fuffer the glals to lye betwixt them clear o£. all contaft with any other body, as far regards their upper furface: the bottom plate, neverthelefs, mull have ho .pillars ; as there will be nothing under it, but the~lubftance of the-coffin. Thefe iron plates mull be mad^ lb much bigger than the plates of glafs; that the latter may lye upon them clear of the pillars, which Ihould reft on the iron plates under them, and.not on the glaft../ The iron* plates being, in this manner, adapted to the coffins, the bottom mull be put into it, and one of the plates of glafs laid Upon that; ibut, at fuch an exa£t diftance from each fide, that the pillars of the tnext iron plate may not reft upon it, but on the bare part of the iron plate under it; another plate of glafs mull be then- laid; in the fame manner on this plate of iron; and the fame proceeding continued till the coffin be filled: and then the lid mull be luted on; and the lame method obferved in all other particulars as was before directed for the burning enamel paintings. As there, may be occafion, however, to ufe larger coffins for punted glafs than enamel, the dinjenfions of the furnace mu ft, when fuch are wanted, fee varied accordingly : but it wife not be necefi* fery to iniarge the area of that part of tfife for** niace, which contains the fewel in depth y for if it be irtereafed in length, from fide ter fide, in proportion to the increafed magnitude of the coffins, it will fufficiehtly augment the< bdd/«f firje.