The rough gold is put into a stone crucible, melted, and poured into a mould which gives it the right width for rolling. About 5 oz. of gold is generally moulded at a time. It is then run through rollers, the pressure of which is so great that the little bar of gold that is 1 in. wide and about 3 in. long, after being run through several times, becomes a strip about 14 yds. long and about the thickness of a hair. The strip is then cut into 1 in. squares. These squares are put into what is called a "cutch." This cutch is composed of 180 skins 3 1/2 in. square. The material that these skins are made of is an invention of French origin, and is kept secret. Formerly vellum was used. A gold square is placed between each skin, one directly over the other, until the cutch is filled. Two parchment bands are put over them in opposite directions to keep them from shifting. The cutch is then beaten for 15-20 minutes with a 16 lb. hammer. The gold is then taken out of the skins, quartered by a skewer, and put into what is called the "shoder." The number of skins in a shoder is 680,

If the enamel breaks, and the iron bends towards the enamelled side, and the contraction of the enamel is there, fore greater than that of the iron, the constituents must be altered in the opposite sense. The following relations by weight give, according to Petrik, good and reliable enamels: -

These skins come from what is called the "bung gut" of an ox, one animal furnishing but two skins. The shoder skins are 4 in. square. They are put between the skins in the same manner as in the cutch. They are then beaten for \\ hours with a 10 lb. hammer, taken out, and again quartered with a piece of reed. They are then put into the mould one over the other, as before, until the 900 skins which the mould contains are filled. This is beaten with a hammer weighing 7 lb. for 3-4 hours. The leaf is then ready to be trimmed and booked. Before the beating process, the skins are heated and primed to prevent the leaf from sticking. Heated presses are used to take the moisture from the skins. Each skin is rubbed with a hare's foot with plaster of Paris on both sides before beating. Each one of the first squares of gold beaten out makes 25 leaves, or one book. The trimming of the leaves before they are put into books is done by a sled-shaped machine called a wagon. The trimming and booking is done mostly by girls. The trimmings that are left from the leaves are scraped together and melted over. A little salt added makes it thoroughly clean.

The granite block that the beating is done on is about 3 ft. high, the top surface being ground down perfectly smooth, so as to prevent the blows of the hammer from cutting the under side of the mould. The operations are well shown in the illustration on p. 242. (Scient. Amer.) Moulding and Casting. - Moulders' Tools. - These comprise the rammer, vent wire, trowel, various cleaners, bead and flange, and similar tools used for sleeking, and finally the workmen's hands. Simple though these may appear, their proper employment involves a knowledge, of the first principles of the art of moulding. The workmen's hands are purposely included, because in the making of a mould very much often depends on the way in which the hands are used. Tools will often damage a mould, the hands seldom do; the sense of touch is more reliable than the pressure of a tool, and for this reason a. good moulder seldom uses the latter when his hands can be of service. Thus, in making an uneven bed for the bedding down of a pattern, the whole surface will be gone over in detail with the hands, in order to judge of its equal consistence, or otherwise; soft places are rendered firm by pressure and the addition of more sand, and the surface is roughened by rubbing the palms of the hands to and fro over it.

210

Gold beating.

Sand is tucked under flanges and ribs and into angles by the hand; pouring basins, too, are rounded up with the palms of the hands and fingers, as well as runner and riser heads. Broken parts are mended better and safer with the finger than with the trowel, loam is daubed on by hand, small patterns are lifted out by the fingers better than with spikes; in fact, the hands of a moulder are of exceptional use to him.

There are two types of rammers employed, the " pegging" and the " flat rammer," and each is used in different sizes, a (Fig. 211) shows a pegging rammer, and the size of the flat end piece by which the sand is punched may vary from 1 in. by 3/8 in. to 3 in. by 1 in.; b represents a modified form, a being capable of going into narrower spaces than 6. For ramming between very narrow spaces, such as the teeth of small gear wheels, and for small cores, a simple round rod of iron is often used. The bulk of the work is done with these pegging rammers, c being reserved for finishing off the sand to an approximately level face with the face of the flask or pattern, as the case may be, and for levelling beds. .

The flat rammer d represents the largest size used, ranging from 5 in. to 6 in. diameter; and is fitted with a wooden handle, the others having iron handles. It is used for going over the largest surfaces and for filling in the sand around boxes placed in foundry pits. The handle is self-wedging, as shown at e\ the hole being tapered, the head of the wedge touching on the bottom of the hole drives the cleft handle outward, filling up the enlarged tapered space. On the proper use of the rammer depends in a large measure the successful issue of the work in hand. Ramming must be done wisely, with due regard to the character of the mould and the position of the section which is being rammed.

Molten metal always has a tendency to fly off from a hard surface, because the gas generated from the moisture present cannot get away readily, but forms a cushion between the metal and the mould. In a hard rammed open sand mould which is not vented, the gases will be seen bubbling up through the iron, giving rise to little jets or fountains of metal. In a closed mould, the bubbling of the metal against a hard surface from which the air cannot escape with sufficient rapidity will break away the sand in patches, causing scabbing. In chilled moulds, not properly dried and warmed, the metal will blow out. For this reason, a green sand mould should always be rammed only as hard as is necessary to sustain the pressure of metal. The pressure of metal is always greatest on the bottom, and when the depth becomes very great, dry sand moulds are preferable for this reason. But with green sand moulds of moderate depth a hard bed is necessary to withstand the pressure of metal, and then the practice is to ram a hard bottom stratum, and over this a thin stratum of softer and more open sand. Bubbling at the surface is thus prevented, as the gas gets through the more open sand into the denser body or backing below, which is well vented, the venting being proportional to the hardness of the bed.