The drawing is taken from a petal of Pelargonium prepared by myself.
There is yet one point in the petal which the star-stipple has not touched, and probably cannot touch. I mean the slight projection of the stipple-hairs, which give an effect of light and shade as well as mere flat softness.
Plaster Casts.
We have already mentioned the electrotype, and may now come to a branch of art which is much associated with it, namely, the Stereotype.
As many of my readers may know, types are very valuable articles, and must not be wasted. If, therefore, a book should be thought likely to have a steady sale, much of its value would be lost if the types were kept standing, inasmuch as they could not be used for any other work.
In such cases the Stereotype is employed. Omitting minute details, the process is as follows:—
The type, ready set up, is carefully oiled. Plaster of Paris mixed with water is then poured into a shallow trough, and the type pressed into it. In a short time the plaster hardens, and the type is withdrawn. The plaster mould is then baked, to drive off all moisture, and type metal is poured into it. Thus a solid mass is procured, instead of a number of separate pieces, so that there is no danger of disturbance, and the whole block can be multiplied ad libitum if needed. This process sets free the types, which can be broken up and used again.
The ordinary method of taking plaster casts is nearly the same as that which has been described. The object to be cast is oiled, and plaster of Paris carefully applied to it. When it is “set,” the plaster “mould” is removed and dried. The process is then reversed, the interior of the mould being oiled, and plaster poured into it, so as to produce an exact reproduction of the original.
In Nature we have almost exactly the same process, although it is necessarily conducted in a much slower manner.