ENAMELLING. 



585 



Knamelling. clean water. The pestle is then to be wiped perfectly 

 > -"~ - ,~ i ' clean, and, being grasped by the middle with the left 

 hand, the right hand placed on the top, and pressing 

 against the right breast, the operator thus leaning 

 over the mortar, must give a kind of twisting motion 

 10 the pestle, by bringing the right elbow round the 

 pestle, forming the axis of the circle ; while the body, 

 being permitted to rise a little after each twist, fresh 

 particles of the enamel will fall under the pestle, and 

 be completely crushed. This part of the operation 

 should be continued as long as any large pieces of the 

 enamel are felt under the pestle ; for it should be ob- 

 served, that if this great pressure, or breaking down, as 

 it is technically called, is pursued beyond the proper 

 time, some parts of the glass would be reduced to al- 

 most an impalpable powder, while the other part would 

 remain comparatively coarse. To prevent this uneven- 

 ness, the pestle should be held firmly down in the mor- 

 tar, with the left hand grasping it as before, while the 

 right hand gives a circular motion to the upper part, 

 at the same time using as much strength ES can lie con- 

 veniently exerted. In a very short time after this me- 

 thod is begun, the large pieces that have escaped the 

 pestle in breaking down, will present themselves under 

 the pestle, and cause it to jump and twist in contrary 

 directions. This may be prevented, by feeling for 

 them with the pestle, and crushing them against the 

 side of the mortar, holding it at the same time firmly 

 with the left hand. As the fine flour, into which some 

 parts of the enamel is ground, would prevent the rest 

 from being evenly ground, it must be washed away 

 four or five times during the grinding. This is best 

 done by nearly filling the mortar with clean water, and 

 agitating the enamel with the broad flat spatula, stir- 

 ring it from the bottom till the water appears quite 

 milky ; the enamel should then be suffered to settle to 

 the bottom, and the water poured off. A small quan- 

 tity of water must then be put into the mortar, suffi- 

 cient to keep the enamel from clinging to the sides of 

 the pestle, and the grinding continued till there ap- 

 pears a difficulty of getting the pestle to touch the 

 bottom of the mortar. When it is arrived at this state 

 of fineness, the pestle must be held in the middle with 

 the right liand, giving it a circular motion, clearing the 

 enamel from the sides of the mortar at each revolution. 

 When this kind of motion is begun, it will be necessa- 

 ry to hold the mortar with the left hand, taking grrat 

 care not to throw the enamel over the sides, because the 

 dirt that it would contract by such an accident could not 

 be got rid of without an infinitedeal of trouble, besides the 

 risk of breaking the work in getting the specks from the 

 surface of the dial plates, when the enamel has been fired. 

 As it would be almost impossible to lay down a certain 

 rule for the fineness to which the glass enamel should 

 be ground, as different parcels, or pots, (as they are 

 called at the glasshouse, ) require to be varied, we can 

 onlj ay, that the finest should never exceed fine grain 

 gunpowder, while the coarsest must never be left lar- 

 ger than maw-seed. When the enamel is completely 

 ground, wash the flour thoroughly from it, and put it 

 in the basin, then keep it covered with water till it is 

 wanted for use, taking great care that it receive no 

 dust or dirt. 



Method of JVf c /^o</ of grinding the Venetian Hard F.nnmcl.for the 



VeS. Bottoms or wider Hides of the Dials. 



h "j d f ' na " h This enamel is to be broken with the hammer in the 



lotion's 'of same manner as the glass enamel; but, instead of break- 



<IMX. >ng >t down in the agate mortar, it should be done in 



VOL. VIII. PART II. 



one made of iron, of a cylindrical form. The bottom of EnameHin*. 

 the mortar should be faced with steel, possessing a small S ""Y "" 

 degree of concavity, that the enamel may return to the 

 centre after each blow. The pestle should be about 

 one inch and a fourth in diameter, and about six inches 

 long, with the face of steel, about one inch and a half 

 in diameter, and a little convex, to suit the mortar. The 

 depth of the mortar should be about four inches ; and 

 with respect to thickness, as there will be no strain 

 upon the sides, the lighter it is made the better. It 

 should also be observed, that the arris of the face of the 

 pestle should be rounded, so as to leave no sharp edge* 

 near the part where it comes in contact with the ena- 

 mel, as they would be soon broken off,ancl spoil the other 

 part of the face. After the enamel has been broken 

 with the hammer, it must be put into the steel mortar 

 in small quantities, and pounded till it is as fine as the 

 glass enamel, (when it has been broken down in the 

 agate mortar); it should then be put into the agate 

 mortar, and ground till it appears to be reduced almost 

 to an impalpable powder. It must be remembered not 

 to wash the enamel that is to be used for bottoms, as 

 the flour will, in this case, be more serviceable than de- 

 trimental. When this enamel is ground, put it into a 

 clean gallipot, and always keep it covered with water ; 

 for observe, if ever it gets dry after it is ground, it 

 will be necessary to give it two or three turns in the 

 agate mortar, otherwise the enamel is likely to blister 

 in the fire. 



Melliod of grinding and pickling the Venetian Hard Ena- 

 mel that is to be used for the Tops of Dial Plates. 



When a piece of enamel is chosen for hard plates, McUu>d of 

 great attention should be paid to the colour, that which ^"j" 1 ."^. 

 is the whitest being considered the most valuable. The the Vcnc" S 

 piece that is to be ground must be laid upon a clean tian hard 

 planch (or, what would be much better, a thin plate of enamel for 

 platina), and placed under the enameller's muffle till it * e to P* 01 ' 

 is red hot ; it must then be quickly drawn from the dia!f< 

 fire, and quenched in very clean spring water. This 

 will cause the enamel to fly into very small pieces, 

 which must be collected and put into the agate mortar. 

 The intention of breaking the enamel in this way, is to 

 do away, as much as possible, the necessity of using the 

 hammer and steel pestle ; because, if any small particle 

 of the steel gets into the enamel, it will cause much 

 trouble to get it out. The method of grinding it is 

 just the same as that employed for the other hard ena- 

 mel, excepting that this must be rather coarser ; and 

 great care must be taken, when the enamel is washed, 

 not to throw away the water which contain the flour, 

 which may be collected after it has settled, and put 

 into the gallipot with that whicli is to be used for bot- 

 toms. When the enamel is ground fine enough, it must 

 be put into a wide-mouthed glass bottle with a glass 

 stopple, and covered with strong nitrous acid; and in 

 this state it should remain till wanted for use. 



Method of enamelling tvilh the Soft Glass Enamel. 



The napkin that is to be used for laying or spread- Method of 

 ing the bottoms, must be laid on the work-board four enamelling 

 times doubled. The copper is to beheld in the left with Ule soft 

 hand, with the feet upwards, and a small quantity of 

 the hard enamel for bottoms is to be taken out of the 

 gallipot on the end of the bottom spatula, and spread 

 roughly on the copper, covering it closely up to the 

 feet and centre holes. It must then be laid between the 

 folds of the cloth till a little of the water is absorbed, 

 4 E 



ena- 



