In these experiments, the mould was made in “green sand” in the ordinary manner, and the fabric laid smoothly upon one face, being cut slightly larger than the mould, in order that it might project over the edge, so that when the moulding flask was closed, the fabric was held in its proper position.  As the molten metal flowed into the mould, it forced the fabric firmly against the sand wall, and when the casting was removed, the carbonized fabric was stripped off from its face without injury.  In this way several castings have been made from one carbonized material.

These castings are as sharp as electrotypes, whether made of soft fluid iron or of hard, quick-setting metal.  This peculiarity is owing to the affinity between molten iron or steel and carbon.  The molten metal tends to absorb the carbon as it flows over it, thus causing the fabric to hug the metal closely.  It is somewhat analogous to the effect of pouring mercury over zinc.  You know that when mercury is poured upon a board, it runs in a globular form, it does not “wet” the board, so to speak; but when poured upon a plate of clean zinc, it flows like water and wets every portion of the zinc, or, as we say, it amalgamates with the zinc.  So when molten iron is poured into an ordinary sand mould, which has been faced with this refractorily carbonized fabric, it wets every portion of it, tending to absorb the carbon, and doubtless would do so if it remained fluid long enough, but as the metal cools almost immediately, there is no appreciable destruction of the fibers.

The casting which I shall now exhibit represents a very interesting and novel experiment.  In this case, the piece of lace, having open meshes a little larger than a pin’s head, instead of being laid upon one face of the mould, was suspended in it in such a way as to divide it into two equal parts.  Two gates or runners were provided, leading from the “sinking head” to the bottom of the mould, one on each side of the lace partition.  The molten iron was poured into the sinking head, and flowing equally through both runners, filled the mould to a common level.  The lace, which was held in position by having its edges embedded in the walls of the mould, remained intact.  When the casting was cold, it was thrown upon the floor of the foundry and separated into two parts, while the lace fell out uninjured, and the pattern was found to be reproduced upon each face of the casting.

The question naturally arises, Why did not the iron run through the holes and join together?  The answer may be found in the fact that the thin film of oxide of iron, or “skin,” as it is popularly called, which always forms on the surface of molten iron, was caught in these fine meshes, and thus prevented the molten metal from joining through the holes.  I have repeated the experiment a number of times, and find that the meshes must be quite small (not over one fiftieth of an inch), otherwise the metal will reunite.