It is often advisable to lay thin card-board or strong paper under the fins, if the clay is so soft as to come up over the edges. Having now nicely built in the fish — the upper surface of the clay being carefully smoothed over with a knife-blade and a stiff brush ("Artist's hog-hair, No. 8") dipped in water, surround the clay with pieces of board, set up on edge, so as to form a wooden wall around all; the height of this wall should exceed the greatest depth or thickness of the fish by some inches. Tie these four walls — planed on their inside surface — around with strong string, finally nailing outside all with long "French" nails, driven into the table as a support against pressure from within. Look all over carefully, and if any open spaces appear between the clay tablet and the boards, fill in with more clay.
The fish being now ready for casting, take a bowl, which half fill with clean water, into this "dust in" the fine plaster of Paris, in small quantities at a time, stirring each portion until all is ultimately mixed smoothly and without lumps; when enough is mixed — and the knowledge of quantity only comes with experience — pour it quickly, yet gently, over the whole surface of the fish; jarring the table with your fist causes the plaster to settle down more evenly, without leaving "blowholes." The plaster should now be an inch or more in thickness over the highest portion of the fish, in order to give sufficient strength for the "return" cast. Should this not be so, mix some more plaster and strengthen the cast, endeavouring to get a flat surface on the top.
After ten minutes, take away the nails and boards, thus allowing more air to get to the mass of plaster. In half an hour — should the plaster be of good quality — the mould may be raised, turned over, and the fish will tumble out, or may be pulled carefully out without the least trouble. Remove the clay, and on looking into the mould it will, if properly made, show every scale and every line, be free from "blow-holes" or blemishes of casting, besides having a fairly even and square surface surrounding the cavity from whence the fish has been extracted.
This first mould can be cast into again by plaster of Paris, and will, in the case of most fishes, turn out a satisfactory reproduction of the original. Some fishes there are, however, so curiously shaped as to make the first or "female" mould so "undercut" as to render it impossible to get a return cast. In this case, nothing avails but the destruction of the first to release the copy. There are several ways of doing this; one of the most simple is sawing with many cuts the edges of the first, or, as it now becomes, the "waste" mould as near to the cavity as you dare, before casting into it; having done which, and allowed several hours, or a day even, to elapse, you proceed to break it away, piece by piece, by gentle blows with a hammer, leaving the enclosed fish to make its appearance little by little. When this plan is adopted, the last cast or copy must be run double the thickness to that you wish to destroy, otherwise you may break the copy instead of the "waste" mould. Another way is to make the first mould very thin, or to put thin successive coats of plaster over the fish, with brown paper between each coat, and subsequently breaking them away, layer by layer, after the fish is extracted and the mould is filled in by plaster.
In casting into the first mould for the "copy" or perfect cast, it will, of course, be necessary to lay it concavity uppermost, and to surround it with a wall of board like the last, brushing over the concavity, and indeed the whole of the tablet surrounding it, with soft soap and water, or oil, or thin pipe-clay and water; or, if the mould has been baked dry, soaking it in water alone will be sufficient to prevent the copy sticking. Recollect that the flatter the tablet — surrounding the cavity left by the fish — is made, the better will be that of the model.
Supposing that your cast, or model fish, has been turned out in good condition, you will see that there are still certain inequalities of the tablet, and certain roughnesses around the fins, mouth, etc..; these latter must be "relieved" and undercut by the aid of the "undercutting" and "relieving" tools (see Figs. 29 and 30), the tablet must be pared flat by a long broad flat chisel called a "firmer," and the edges also nicely squared.
Your fish is now in high relief on a flat background, but, though having correct form, it still lacks colour. How to colour plaster satisfactorily is a puzzle which has perplexed more persons than taxidermists. Speaking for myself, I say that, having coloured the cast, when wet and when dry, with water-colours, used paper varnish when dry, with water-colours and varnished and painted, and painted and varnished the cast in oils, having used "mediums," tempera painting, "secco" — yet I am not satisfied; there appears a want of softness and brilliancy; probably the electro-type or wax process I am now trying may give the desired effect.
So disgusted was I at the seeming impossibility of getting "tone" on plaster, that I determined to try paper for the last cast or model; to this end I took lessons at a theatre in the art of "making (paper) faces," with the result that I now employ paper whenever practicable, and find it answer, from a 2 lb. perch to a 2 cwt. skate. Two or three most valuable results accrue from the substitution of paper for plaster. First, extreme lightness combined with strength; and secondly, of course, excellence of detail and facility of colouring in either water or oil. For remarks upon the artistic mounting of fishes, see Chapters XII., XIII., and XIV.
There are, I find, two excellent articles on fish-casting in "Science Gossip for 1878," to which I must refer my readers for further details. They agree to differ, however, in one important particular. One writer says that plaster-work is as "cleanly as any cooking operation, and there is no reason why ladies should not engage in it"! The other writer speaks of it as "filthy," and, really, I feel inclined to back his opinion; for having now used some tons of plaster, ranging in quantities from a few pounds to 3 cwt. at a time, I must say that, of all the diabolical messes for getting into the hair or on the boots, and about a house or workshop, plaster is the worst. "Matter in the wrong place," ma foi! you can't keep it in the right.
I see that Mr. Taylor, amongst other suggestions, advises the use of half glue and treacle (see Chapter XII.) to cast the first mould for groups of small fishes. If these glue-moulds were backed with plaster "piece-moulds," they might be useful for larger "undercut" specimens.