FILLING.—Brush the sand from the mold, and if the upper edge is uneven, smooth it with a knife so that it will be perfectly straight. Should there be any rough places on the inside of the mold, carefully scrape them down with the skin scraper.
Cut out roughly a piece of soft pine one-half to one inch thick the shape of the outline of the fish, but somewhat smaller, using the mold as a guide. One side will, of course, be flat, and that side should be uppermost when placed in the mold. Work up with water a sufficient quantity of clay to about the consistency of fresh putty. Place the mold on your bench or table, resting it on something soft (such as a piece of old carpet or burlap) to prevent its breaking. Drain the water from the skin and put it back into the mold, adjusting it nicely. The median line will guide you. See that the head, fins and tail occupy the same places they did before. Pour a little alcohol on the skin inside and let it run along the bases of the fins and tail, over the entire inner surface of the skin and into the head to preserve any bits of flesh that may possibly remain. Drain off the surplus alcohol. Fill the adipose fin (if the fish has one) with clay. Sprinkle powdered arsenic over the entire inside of the skin and head. Do not use more than will readily adhere.
The chances are that you removed more or less of the silvery lining of the skin. Whether you did or not, cover the entire inner surface of the skin of the cheek and body with two or three thicknesses of aluminum leaf. Do not cover the entire surface at once. Cover a small part at a time, and then put on top of the leaf enough clay to cover it, commencing at the head and continuing to the tail. Replace the muscles and cartilage of the head with clay. Be sure to keep the skin properly adjusted to the mold. See that the fins and the tail remain in their proper places and that they are kept covered with wet cloths.
Flatten out the clay (a small quantity at a time) with the fingers and cover the inside of the skin to the depth of about one-eighth of an inch, pressing it down firmly, especially at the bases of the fins and tail and into the cheek and head. Fit in the piece of pine, cutting it down as may be necessary. Its shape will be something like Fig. 6.
Mix some more plaster, and before putting in the piece of board, pour in the plaster on the clay, filling the skin perhaps two-thirds full. Quickly, before the plaster sets, put in the piece of wood, carefully pressing it down into the plaster until it is level with the upper edge of the mold, removing any surplus plaster quickly and neatly. Sew up the skin from one edge to the other as shown in Fig. 7.
REMOVING SPECIMEN FROM MOLD AND DRYING.—Lay a piece of clean board of the proper size on top of the mold, turning both over. Lift up the mold a trifle, gently shaking it. The fish may or may not come out. If not, turn the mold back, insert the point of a knife in the wood and try to start the fish. In extreme cases it may be necessary to break the mold carefully. However, there should be no undercuts to hold the fish.
Carefully wash the fish as it lays on the board to remove all clay and plaster which may be on the upper surface. With the fingers smooth out any wrinkles or uneven places. Sometimes, when drying, small wrinkles or bubbles may appear in the skin of such fish as trout, but they will soon disappear. If you placed the fish in a natural position when making the mold and properly adjusted the cleaned skin to the mold, there should be no wrinkles.
Place thin pieces of wood the shape of the fins between the board and the dorsal and anal fins, which should stand out from the board a little way. Cover the tail and the fins which lie flat with thin pieces of wood, pinning them to the board until dry. The fins which do not lie flat should be spread between thin pieces of wood held in place with pins or clips.