MODEL, in a general sense, signifies an original pattern, proposed for any one to copy or imitate.

This word is particularly used, in building, to signify an artificial pattern made in wood, stone, plaster, or other matter, with all its parts and proportions, being intended for the better conducting and executing some great work, and to give an idea of the effect it will have in its proper dimensions. In all great buildings, it is much the surest way to make a model in relief, and not to trust to a bare design or draught. There are also models for the building of ships, and for many other purposes.

Models are likewise used in painting and sculpture; and hence, in academies, they give the term model to a naked man or woman, disposed in several postures, to afford an opportunity to the scholars to design them in various views and attitudes. . . ∙

Models in imitation of any natural or artificial substance are most usually made by means of moulds composed of plaster of Paris. For the purpose of making these moulds, this kind of plaster is much fitter than any other substance, on account of the power it has of absorbing water, and soon condensing into a hard substance, even after it has been rendered so thin as to be of the consistence of cream. This happens in a shorter or longer time, according as the plaster is of a better or worse quality; and its good or bad properties depend very much upon its age, to which, therefore, particular regard ought to be had. It is sold in the shops at very different prices, the finest being made use of for casts, and the middling sort for moulds. It may be very easily coloured by means of almost any kind of powder excepting what contains an alkaline salt; for this would chemically decompose the substance of the plaster, and render it unfit for use. A considerable quantity of chalk would also render it soft and useless, but lime hardens it to a great degree. The addition of common size will likewise render it much harder than if mere water is made use of. In making either moulds or models, however, we must be careful not to make the mixture too thick at first; for if this be done, and more water be added to thin it, the composition must always prove brittle and of a bad quality.

The particular manner of making models, or casts, as they are also called, depends on the form of the subject to be taken. The process is easy where the parts are elevated only in a slight degree, or where they form only a right or obtuse angle with the principal surface from which they project; but where the parts project in smaller angles, or form curves inclined towards the principal surface, the work becomes more difficult. This observation, however, holds good only with regard to hard and inflexible bodies; for such as are soft may often be freed from the mould, even although they have the shape last mentioned. But although this be the case with the soft original substance, it is not so with the inflexible model when once it is cast.

The moulds are to be made of various degrees of thickness, according to the size of the model to be cast; they may be from half an inch to an inch, or, if very large, an inch and a half. Where a number of models are to be taken from one mould, it will likewise be necessary to have it of a stronger contexture than where only a few are required; and this for very obvious reasons.

It is much more easy to make a mould for a soft substance than a rigid one, as in any of the viscera of the animal body; for the fluidity of the mixture makes it easily accommodate itself to the projecting parts of the substance; and as it is necessary to inflate these substances, they may be very readily extracted again by letting out the air which distended them.

When a model is to be taken, the surface of the original is first to be greased, in order to prevent the plaster from sticking to it; but if the substance itself be slippery, • as is the case with the internal parts of the human body, this need not be done. When necessary, it may be laid over with linseed oil, by means of a painter’s brush. The original is then to be placed on a smooth table, previously greased or covered with a cloth, to prevent the plaster from sticking to it; then the original is surrounded with a frame or ridge of glaziers’ putty, at such a distance from it as will admit the plaster to rest upon the table on all sides of the subject for about an inch, or as much as is sufficient to give the proper degree of strength to the mould. A sufficient quantity of plaster is then to be poured as uniformly[7:15:312] as possible over the whole substance, until it be everywhere covered to such a thickness as to give a proper substance to the mould, which varies in proportion to the size. The whole must then be suffered to remain in this condition until the plaster has attained its hardness. When the frame is taken away, the mould may be inverted, and the subject removed from it; and when the plaster is thoroughly dry, let it be well seasoned.

The moulds being thus formed and seasoned, they must next be prepared for the casts by greasing the inside of them with a mixture of olive oil and lard in equal parts, and then filled with fine fluid plaster, and the plane of the mould formed by its resting on the surface of the table covered to a sufficient thickness with coarse plaster, to form a strong basis or support for the cast where this support is requisite, as is particularly the case where the thin and membranous parts of the body are to be represented. After the plaster is poured into the mould, it must be suffered to stand until it has acquired the greatest degree of hardness it will receive; after which the mould must be removed: but this will be attended with some difficulty when the shape of the subject is unfavourable; and in some cases the mould must be separated by means of a small mallet and chisel. If by these instruments any parts of the model should be broken off, they may be cemented by making the two surfaces to be applied to each other quite wet, then interposing betwixt them a little liquid plaster, and smoothing the joint after being thoroughly dry. Any small holes which may be made in the mould can be filled up with liquid plaster, after the sides have been thoroughly wetted, and smoothed over with the edge of a knife.

In many cases it is altogether impracticable to prepare a mould of one piece for a whole subject; and therefore it must be considered how this can be effected in such a manner as to divide the mould into the fewest pieces. This may be done by making every piece cover as much of the pattern as possible, without surrounding such projecting parts, or running into such hollows, as would not admit a separation of the mould. It is impossible, however, to give any particular directions in this matter which can hold good in every instance, the number of pieces of which the mould is to consist being always determined from the shape of the pattern. Thus the mould of the human calculus will require no more than three pieces, but that of an os femoris could scarcely have fewer than ten or twelve. Where any internal pieces are required, they are to be first made, and then the outer pieces after the former have become hard.

To make a mould upon a hard and dry substance, we must, in the first place, rub the surface of it smoothly over with the mixture of oil and lard above mentioned. Such hollows as require internal pieces are then to be filled up with fluid plaster; and whilst it continues in this state, a wire loop must be introduced into it, by which, when hardened, it can be pulled off. The plaster should be somewhat raised in a pyramidal form around this wire, and afterwards cut smooth with a knife whilst yet in its soft state; preserving two or three angular ridges from the loop to the outer edge, that it may fix the more steadily in the outer piece of the mould to be afterwards made upon it. Let the outer piece then be well greased, to prevent the second piece from adhering; the loop being enclosed with some glaziers’ putty, both to prevent the second piece from adhering, and to preserve a hollow place for the cord.

To form the second or outside piece, mix a quantity of plaster, proportioned to the extent of surface it is to cover and the intended thickness of the mould. When it is just beginning to thicken, or assumes such a consistence as not to run off very easily, spread it over the internal piece or pieces as well as the pattern, taking care at the same time not to go too far, lest it should not deliver safely; and as the plaster becomes more tenacious, add more upon the pattern, until it has become sufficiently thick, keeping the edges square and smooth like the edge of a board. The plaster should be spread equally upon all parts, which is best done by a painter’s pallet knife or apothecary’s bolus knife; but for this the instrument should be somewhat less pliable than it is commonly made.

When the outside piece becomes hard, the edges are to be pared smooth, and made nearly square with a small pointed knife. Little holes of a conical shape are to be made with the point of a knife, about an inch distant from one another, according to the size of the piece. These are designed to receive the fluid plaster in forming the adjacent parts of the mould, and occasion points corresponding to the hollows; and they are intended to preserve the edges of the different pieces steadily in their proper relative situations. The third piece is then to be formed in a manner similar to the second, greasing the edges of the former plentifully with hog’s lard and oil, to prevent the pieces from adhering to each other. Thus the pattern is to be wholly enclosed, only leaving a proper orifice for pouring in the plaster to form the model; small holes being also bored in the mould opposite to the wire-loops fixed in the inside pieces, through which a cord is to be conveyed from the loop to confine such pieces during the time of casting. In some cases, however, it is not necessary that the mould should totally enclose the pattern; for instance, where a model is to be made of a pedestal, or a bust of any part of the human body. The bottom of such moulds being left open, there is accordingly ample room left for pouring in the plaster.

After the mould is completely formed, it is next to be dried either naturally or by a gentle artificial heat, and then seasoned in the following manner. Having been made thoroughly dry, which, if the mould is large, will require two or three weeks, it is to be brushed over plentifully with linseed oil boiled with sugar of lead, finely levigated litharge, or oil of vitriol. The inside and joints of the mould should be particularly well supplied with it. If the mould be large, it is needless to attend to the outside; but when the moulds are small, it will not be improper to boil them in the oil, by which means their pores are more exactly filled than could otherwise be done. After the moulds have undergone this operation, they are again set by to dry, when, being greased with olive oil and hog’s lard, they are fit for use. If linseed oil be used for greasing the moulds, it will in a short time impart a disagreeable yellow colour to the casts.

The mould being properly prepared and seasoned, nothing more is requisite to form the model than to pour into it the finest liquid plaster of Paris. After a layer of this, about half an inch in thickness, has been formed all round the mould, the coarser kind may be used to fill it up entirely, or to give to the model the thickness required.

Besides the models which are taken from inanimate bodies, it has been frequently attempted to take the exact resemblance of people whilst living, by using their face as the original of a model from which to take a mould; and the operation, however disagreeable, has been submitted to by persons of the highest ranks in life. A considerable difficulty occurs in this, however, by reason of the person being apt to shrink and distort his features when the liquid is poured upon him; neither is he altogether without danger of suffocation, unless the operator understand his business thoroughly.

To avoid the former inconvenience, it will be proper to mix the plaster with warm instead of cold water, by which means the person will be under no temptation to shrink; and to prevent any danger of a fatal accident, the following method is to be practised: Having laid the person [7:15:313]horizontally on his back, the head must first be raised by means of a pillow to the exact position in which it is naturally carried when the body is erect; then the parts to be represented must be very thinly covered over with fine oil of almonds by means of a painter’s brush; the face is then to be first covered with fine fluid plaster, beginning at the upper part of the forehead, and spreading it over the eyes, which are to be kept close, that the plaster may not come in contact with the globe; yet not closed so strongly as to cause any unnatural wrinkles. Then cover the nose and ears, plugging first up the meatus auditorius with cotton, and the nostrils with a small quantity of tow rolled up, of a proper size, to exclude the plaster. During the time that the nose is thus stopped, the person is to breathe through the mouth. In this state the fluid plaster is to be brought down low enough to cover the upper lip, observing to leave the rolls of tow projecting out of the plaster. When the operation has been thus far carried on, the plaster must be suffered to harden ;,after which the tow may be withdrawn, and the nostrils left open and free for breathing. The mouth is next to be closed in its natural position, and the plaster brought down to the extremity of the chin. Begin then to cover that part of the breast which is to be represented, and spread the plaster to the outsides of the arms and upwards, in such a manner as to meet and join that which has been previously laid on the face. When the whole of the mass has acquired its due hardness, it is to be cautiously lifted, without breaking or giving pain to the person. After the mould is constructed, it must be seasoned in the manner already directed; and when the cast is taken, it must be separated from the mould by means of a small mallet and chisel. The eyes, which are necessarily shown closed, are to be carved, so that the eyelids may be represented in an elevated posture; the nostrils must be hollowed out, and the back part of the head, from which, on account of the hair, no mould can be taken, must be finished according to the skill of the artist. The edges of the model are then to be neatly smoothed off, and the bust fixed upon its pedestal.

The method of making models in plaster of Paris is undoubtedly the most easy way of obtaining them. When models, however, are made of such large objects that the model itself must be of considerable size, it is vain to attempt making it in the way above described. Such models must be constructed by the hand with some soft substance, as wax, clay, putty, and the like; and it being necessary to keep all the proportions mathematically exact, the construction of a single model of this kind must be a work of great labour and expense, as well as of time.