FURNACE. 
will do; frequently it, however, is nota very oe 
defett, if a {mail crack takes place at the upper part, a 
begets a confidence that the mufile will not crack any ee ; 
owing probably’ to the unequal contra€tion of the parts of 
) 
oO 
manner : the pi ure paitte ’ > and prep oe 
our article PAINTING in a is placed upon a are cr 
flat piece of fire-itone, with m uantity of whiting 
he ufe of which will be explained hereafter. 
e annealing oven H, 
the annealing oven fhou 
from the oil may readily oe ca 
e planch and picture a it are now removed from th 
annealing oven by aniron fork, fig. 7, ufed in a manner ini 
lar toa baker’s peel, and introduced i ate the nufie: the doc 
are fhut clofe; the operator now looks rea ae a {mall hole 
in one of the "doors, furnifhed. with a fliding co ver,, and a 
tentively watches the picture ; he fees it graduall y heat tll 
it acquires the fame colour as ‘the m muffle; the furface of the 
picture is then obferved to affume a glofly tp a“ ariling 
from the fufion of the enamel; at fir mence 
the farther part of themufile, but cxeaule itfelf, enn ston ihe 
ing celerity; over the w hole furface, zs the eae apr is well’ 
conducted. picture is now wit wn fro uf 
upon the oe before its mouth,. ne ieee before a 
ftrong Fede if every al is equally glofly ; if not, it is re- 
turned t muffle ; in this itate the picture and planch: 
only a a mafs at a vailiite heat; no traces of painting ox 
colour can: be difcovered, and the cihiele judgment mutt be 
formed from its appearing equally fufed in every part of the: 
furface 
The “fufing being now completed, the picture is returned 
to the teen oven; and the fire being put out by taking 
away ‘he bars of the: fire, the whole furnace ccols grada- 
ally together, the picture remaining in the oven fome hours 
before it is. remo oved to 
Do +4 
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aae= Fe 
a's 
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fuch a 
ate es ha fon it, and introduced 
into the muffle, may not experience fuch a change e of tempe- 
ratureas to fly.. In Mr. Bone’s furnace this is fo well regu- 
lated, that he feldom finds his paintings crack in the firing, 
though it coft him many fevere difappointments before he ob- 
tained this perfection by repeated trials: this.difpofition to 
crack appears to depend almoft as much upon the plate and 
enamel as t 
Becaufe a painting ftands the firft firings well, _thatat will 
the conftruction of the furnace, and it is no. proof | 
not fly in the So Enamel pictures are nearly all 
liable « to cockle or warp in the firing,.in a grea 
degree, though this may be obviated fo far, by great 
the eee ation of the metal plate, as to be no jerious detri- 
ment to the effect of the coe : the method of eas 
thefe che is explained in the article ENAMELLIXG. 
fee Pana 
4 ubject requiring long experience, 
to be added to the ufual ogee of a painter, as the co- 
lours are in fad p pr ae céd by the firing, being very different 
in appearance when laid on, and without any of the brilliancy 
for which this {pecies of painting is diftineuifhed "The artift. 
its pee eae peu others, 
examine it conftantly by its appeararice : * 
to the perfection of enamel painting, that the colours 
employed fhould blend together in the firing, and at the fame 
or fome would be too much burnt before others w ere. 
properly ia : ae they muft be of fuch a nature as not 
to emit any v v when in the fire, as this.would 1 produce : 
Sere in a ee ce, and deltroy the effet of the painting. . 
As the colours at prefen t known which will ftand thefe - 
tefls are but few, ar 
ia 
a 
ner by os oe 
neue might 
As ee enraity¢ of enan 
plates are ae e with the furface convex, it becomes oe 
fry, when they are large, to fupport the centre of | the plate 
om finking, whic each are very liable to do when ina 
flat te of fufion. ‘T'o prevent this accident, the planch muft | 
have a bed of powdered whiting laid upon it, with its fur- 
face made to fit t 
operation is nicely 
conducted, the plates may be made to keep: their fhape 
much better than by any other means that have as yet been; 
ACE for enamelling hopes Dial-plates. This fur-. 
nace, hough very fimple in its conftruction, differs from all - 
the s we have deferibed in not having any bars or 
eae for the admiffion of air to the } bottom: of the fires 
the only patlage for air being through or under the m mufile, . 
which in this kind of enamelling. a only of a fimple - 
arch of clay without either bottom or back.. 
is ae ace is fingularly aie to’ the purpofe for 
ich iti as a very intenfe ‘heat is obtained with a 
t comparatively {mall quantity of fuel, in addition to w hick 
ork rought almoft in conta@t with the coals 
ered ae any injury from their dirt ; clearnefs in this . 
kind of enamelling : being very juftly son fered one of its 
greateft perfections.. Fig. I. O late Vi of Puriaces, 
reprefents a front clevation; A, A, ar e two aos of brick 
vv “ork, upon which reft the arch B, ing the afh, or - 
of thefe ae i je& the three 
becks D, D; D, which fupport the hearth, or iron plate, E; 
another plate of caft-iron lies jutt beneath ‘his, which a 
for the = of the —— and which m 
the fection at F, fig. Upon th 
the Welfh anes G, c. forming the interior fides of the 
furnace; the one which forms the back may be feen at G, 
S 2m 
