Take now a large piece of charcoal of a close texture, and hollowed out, so that the copper may lie convenient ly in it, and having your lamp near the edge of the board, and the copper placed on the coal, which should be held in the left hand, put the end of the blowpipe into the centre of the flame, and holding the copper nearly under it, give a very slight but steady blast till the copper is red hot. The pipe should now be withdrawn from the centre, that the whole of the flame may be collected, which will be done if the operator blows as hard as he can. When the copper is arrived nearly at a white heat, the centre of the blast must be directed immediately over each of the feet till the solder runs down to the copper, and the soldering is complete. If the feet have kept in their places, they will fit into the holes of the frames; but if they have shifted a little, which will frequently be the case, lit them into the frame, by placing the copper in the setting die with the feet upwards, and the frame tie ing held over the feet, bend them whichever way may he requisite, by introducing the setting spatula between the frame and the copper, pressing it against that side of the foot or feet that may be necessary, till they fit into the holes of the frame. When this is done, the copper is to be gently withdrawn from the frame, and if, upon examining the upper side, any dints or bulges have been made, they must be taken out by putting the copper ii o the setting die, and rubbing the spatuld round the feet till such imperfections arc removed. When a copper is made to a brass edge and frame for a second watch, the second, or eccentric hole, must be made in the fol lowing manner, after the copper has been soldered and set : Place the copper in the brass edge and frame, hold ing the copper downwards on the board, with a fine nee dle or point put perpendicularly through the seconds hole of the frame; prick quite through the copper a very small hole, which must be bulged or raised, by having a corresponding hole drilled in one of the dies. The copper is then to be placed on the die, and the hole that has been pricked, must be placed exactly over the hole that has been drilled in the die. A smaller round ended punch should be used to bulge up the hole, which is to be done in the same manner as was directed for making the holes in the centres of the plain coppers. The hole must be finished by filing the tipper side; and if upon examination it does not correspond with the hole in the frame, it must be made to fit by placing it on the die again, and opening the hole with the point, bearing most on that side that is most out of the centre. It should be observed, that although the plate for a se conds watch is desired to he as flat as possible, yet the copper should be set a little rising ; for if it was not kept up a little in the centre, when the enamel is put on and the plate tired, it would sink in the centre, an im perk etion for which there is no remedy. NN'e would recommend, that all copper used for flat plates should be annealed and planished before they are put to the die. This may be done on a piece of flat marble; and the ham mer should be made of elder, or hard boxwood, having a very smooth face. The use of this operation is to take away the cockling kind of spring, that is always left in the copper when it comes from the flatting mills. To perform this nicely, requires muck judgment in the operator; for if the copper is promiscuously struck with the hammer, it is ten to one but the imperfection is in creased ; therefore to proceed rightly, the copper must be examined, and that part which is found to be the tightest, or least stretched, and upon which the other parts will appear to twist and play, must be hammered till an uniform flatness is obtained. The best method of ascertaining when the spring is gone, is to let the piece of copper fall from a small distance upon the mar ble slab, and if there is no vibration or ringing noise, we may conclude that the operation has succeeded. We should not have been so particular on this point, had we not been convinced of its utility; for if this is not done, the metal will expand unequally in the fire, which will certainly cause the enamel to crack in the fire, or warp in such a manner as to be wholly useless. We must not omit the method of cleansing, (or pickling the copper as it is technically called,) it being necessary in all cases where great nicety is required. This is done, by mak ing a solution of the best double aquafortis and water, about one part of the former to eight of the latter. Put the coppers, as soon as they are all soldered, into as much of the solution as will cover them, and when they have remained two or three minutes, let one of them be taken out and washed in clean water, and brushed with a soft brush and a little white sand. If the scale comes all off, and the topper looks quite bright, they are suffi ciently done ; if not, let them remain some time longer in the solution, and, when brushed as before, dry them with a soft napkin.
Description of the Tools used in Enamelling.
The first is an agate pestle and mortar to grind the enamel. The best kind are those that are most trans parent, and free from opaque spots and veins. See a section of this in Plate CCLII. Figs. 9. 10.
The second is a small hammer about an ounce and a half in weight. One face should be flat, and the other of the shape commonly used in riveting.
The third is a flat spatula seven-eighths of an inch broad, and a little thicker than those used for paint knives.
'Tie fourth is a spatula rather thicker than the last, but of equal breadth. One side of this should be flat, and the other a little curved. This must be made of good steel, and is used to spread the hard enamel on the cop per. See Plate CCLII. Fig. 11.
The fifth is the spatula, for spreading the hard ena mel on the under side of the copper. This is called a bottom spatula. The end of this should be just the same as the end of the setting spatula described in the copper tools, excepting that it should be a little broader.
The sixth is a quill cut just like a tooth-pick. This is used to clear the enamel out of the centre holes of the coppers.
The seventh are two damask napkins, for drying the water from the enamel. These should be very clean, and always kept separate.
Tie eighth is a small bason with a cover, to hold the enamel that is to be used for the tops of the dial plates.
The ninth is a gallipot, to hold the enamel that is to be used for the bottoms, or under side of the dials.
The tenth is a cylindrical block of wood, to fix the cop per on when it is ready to have the enamel laid on the top. This for common sized plates, may be about an inch and half diameter, and about six inches long. On one end of this some soft wax must be fixed, so that it may form a kind of cap to the block, being about one-third of an inch thick on the top, and the same on the sides. See Fig. 12.
The eleventh is a box to hold the plates in, when the enamel is spread on them. This may be about 16 inches long, and 9 broad. The depth may be one inch and a half; but it must not have any side under the opening of the lid.
The twelfth is a small steel-faced anvil to hold in the hand, to break the enamel into small pieces. The face may be about one inch diameter, the other part in pro portion.
Method of grinding the Soft Glass Enamel, called, by Enamellers, Glass.
Take a cake of glass enamel, and with the riveting face of the hammer strike it as near the edge as possi ble, holding, at the same time, the forefinger of the left hand just under the place where the blow falls. By this means, the vibration that would be given to the whole cake will be prevented, and it will be broken into thin flakes. When thick solid pieces happen to fall off, the anvil must be held in the left hand, with the face upwards; and the piece being laid on it, must be broken with the flat face of the hammer, till it is small enough to be ground. To prevent the enamel horn flying about, the anvil should be so held i4 the hand, that part of the fore finger and thumb may form a kind of rim.
The centre is generally the foulest part of the cake, and is often intermixed with black and red streaks. When this is the case, the coloured parts should be re jected, as they would otherwise contaminate the whole enamel. When the enamel is broken as small as is necessary, no piece being left larger or thicker than a small pea, the agate mortar must be set on a piece of coarse linen cloth four times doubled, and made tho roughly wet with clean water. This should be laid on the work-board, and the mortar about half filled with enamel, which should be nearly covered with clean water. The pestle is then to be wiped perfectly 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 to 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 pat tides of the enamel will fall under the pestle, and be com pletely 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 observed, that if this great pressure, or breaking down, as it is techni cally called, is pursued beyond the proper time, some parts of the glass would be reduced to almost an ira palpable powder, while the other part would remain com paratively coarse. To prevent this unevenness, the pestle should be held firmly down in the mortar, 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 as can be conveniently exerted. In a very short time after this method 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, stirring it horn 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 quantity of water must then be put into the mortar, sufficient to keep the enamel from clinging to the sides of the pestle, and the grinding continued till there appears a difficulty of getting the pestle to touch the bottom of the mortar. \Vhen it is arrived at this state of fineness, the pestle must be held in the middle with the right hand, 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 necessary to hold the mortar with the left hand, taking great 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 infinite deal of trouble, besides the risk of breaking the work in get ting the specks from the surface of the dial plates, when the enamel has been fired. As it would be almost im possible to lay down a certain rule for the fineness to which the glass enamel should be ground, as different parcels, or tots (as they are called at the glasshouse,) require to be varied, we can only say, that the finest should never exceed fine grain gunpowder, while the coarsest must never be left larger than maw-seed. \Vhen the enamel is completely ground, wash the flour tho roughly 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.