This section is from the book "Arts & Crafts Magazine Vol1-2", by Hutchinson & Company.
Moulder to the Royal College of Art.
Illustrated With Special Photographs.
Before we begin the actual work of casting, of course we must have decided how many sections our mould is to be divided into," said Mr. Cantoni. "Naturally, the character of the model will decide that," he added, as he proceeded to divide the statuette by a band of clay, in the manner indicated in the photograph on the opposite page - which, however, was taken just as he was completing that operation.
"We shall make our mould in four parts," he said. "One piece will suffice for the front. On account, however, of the iron supporting rod (see page 220), which, of course, will have to be removed, the back must be moulded in two pieces, and the projection of the fingers behind will necessitate our making a separate mould for the hand, which otherwise would certainly come out damaged. An ordinary bust would be moulded in two sections - the back and the front."
He first placed a strip of clay at the back of the head, so that it looked like a hat worn sailor-fashion, and continued the strip all around the figure, so as to bisect it. At the stage of the operation which had been reached when the photograph shown on the opposite page was taken, it will be noticed that part of the clay band hangs behind the model, it having not yet been adjusted.
"By means of this clay strip we shall be enabled later," he said, "to cut open the mould and take the model out. After the front half of our statuette has been moulded, we shall remove the band and apply another like it exactly on the other side of the dividing line. This band must be made very neatly.
" 'How thick and wide must it be?' you ask. That will vary according to the size of the model. For our statuette, which is about three feet high, I have made the band 1/4 inch thick and 1 inch wide.
"We will proceed now to make the front mould. But, first, we must protect the back of our model from possible splashes of plaster," and Mr. Cantoni covered it with a newspaper, which an assistant handed to him after soaking it in a pail of water.
"Let me tell you something about the plaster before we begin, for there will not be much time for talking then, for the plaster hardens very soon after it is mixed, and must be applied immediately. Be sure you have good plaster - the best. You cannot make good bread without good flour, and you cannot make a good cast without good plaster. The plaster must be fresh and dry. Not too dry. Do not keep it near a fire - nor in a damp place either. In the sack or in the tin it should remain good for six months at least. ' What is the best plaster ?' you ask. The English is the harder and is the better for moulding. It is whiter than the French, which is the more creamy. Here is some of each. For casting I use half and half."
Lightly but quickly he sifted the fine white powder through his fingers into a large basin of water, but not before he had first thrown in a little yellow ochre (in powder), thoroughly dissolving it in the water by stirring it with a spoon. Not till then did he begin to sprinkle in the plaster, and not until the plaster was seen rising nearly level in all parts to the surface of the water did he begin to stir it. He called attention to the importance of these points, trifling as they might appear; for, as he remarked, it is the scrupulous observance of such details that brings the process to perfection.
With great expedition he now began to apply to the model the thin, creamy-looking fluid, at first with a bristle brush and then by throwing it on with the hand.
"We have to do this very rapidly while the plaster is in a fluid state like cream - thin cream - so that it will go into every crevice," he observed. "If we should delay until it began to thicken, it would cause distortion of the model. Not more than seven minutes should be taken in applying this coat. In about twenty minutes it will have hardened enough for us to proceed to the next stage. If you are in doubt as to it having reached the proper degree of hardness, put your hand over the surface, which, if the plaster is not yet dry, will be warm to the touch. Not until the surface is cold to the touch will it be properly set."
"You ask 'why I tinted the water before throwing in the plaster?' It is necessary to colour the first layer, so that when, presently, we come to chip away the outer covering of white plaster, we shall be warned that we are getting close to the clay model and must proceed carefully so as not to injure it with the tool.
"The yellow plaster is now dry. You see it varies from 1/4 in. to in. in thickness. Before putting on the next layer, which will be white plaster - that is to say, untinted - we must wash over this first layer with a little clayey water - that is, water with enough clay stirred into it to give it a milky consistency."
Mr. Cantoni dipped a brush into the mixture, and went over carefully every part of the front of the model. "This will be sufficient to separate the layer of tinted plaster from the white plaster, which I am now going to put on," he said. He applied it very freely, explaining that it might be put on thickly now, as it was simply to give strength to the model.
"Our next step will he to protect the model with an armature as with the front. This must be made to follow the lines of the figure," said Mr. Cantoni. He had let his assistant finish covering up the mould with the thick coat of untinted plaster, while he himself had been busy shaping, with a bending iron, to the required inclinations, various lengths of stout iron rod with which finally he formed the armature, as we see it illustrated on page 220. The armature having been placed in position, it was painted with Brunswick black to prevent it rusting. More plaster was added to further strengthen the mould.
Casting in Plaster: A Demonstration.
The front mould (from the outside). The plaster has been strengthened by an armature of iron rods.
" Our front mould now is sufficiently strong, so we will turn the model round and proceed in the same way to make the back mould, starting from the base."
The protecting sheet of newspaper, having served its purpose, was lifted off. Mr. Cantoni first stripped off the clay band from around the model, and with a sharp knife cut away whatever rough projections there were about the margin of the mould. The model was then carefully dusted, and a fresh band of clay was applied to serve the same purpose as before. Numerous equi-distant notches or "keyholes" were then cut in the margin of the mould with a tool resembling a metalworker's drill or bit. These holes were then brushed over with clayey water, like the rest of the mould. Their appearance is indicated on page 220. On page 221 both keyholes and the corresponding "keys" are seen. The latter are formed, as a matter of course, when the plaster is applied to the back moulds.
With a thin layer of tinted plaster the entire back of the model was covered as the front had been, extending right to the outer edge of the first part. This, too, was brushed over with clayey water. Next, throwing up the plaster under the hand at the point marked "A" in the right hand photograph on page 220, Mr. Cantoni, with great care, built up .a support for it. Making this extra piece for the hand will facilitate the removal of the clay model from the mould presently, and the preparation for the casting: the bits of clay on the edge of the mould are placed there so as to allow of the entry of the chisel in prying open the mould.
The mould was now sprinkled with cold water (not clayey), and some was dropped over the top. This was repeated until the plaster was thoroughly saturated and shining with wetness. "The water is very important; without it the model would never come out," Mr. Cantoni remarked. The plaster as soon as it is set is very porous and absorbent, and it takes a great deal of soaking to saturate it sufficiently.
"We are now going to open the mould," said Mr. Cantoni at length, and, having removed will) a knife a little superfluous plaster which was overlapping where the mould should separate, he inserted a chisel at different points and so pried open the mould.
First, the upper part of the back was taken off. The photograph on page 220 shows the appearance of the model at this stage. The separate mould of the hand was carefully removed, and then the half of the back below the supporting iron. The clay model was now pulled, cut, or ripped out piecemeal from the interior of the mould, a knife or whatever other instrument came most handy being used for the purpose. It was really painful to see the assistant slashing away at the carefully modelled torso and mutilating those well-rounded limbs. The poor clay seemed almost human, and to cry out against the outrage. But it all had to come away, and it was with no little difficulty that it was taken off, in great chunks, the interior armature being pulled out with pliers. In getting the clay out, care had to be taken to avoid notching the interior of the mould, for any impressions thus made would produce corresponding defects in the cast, which, however, can easily be repaired. At last the butchery was over, every particle of clay was removed, and the four piece moulds, taken apart and thoroughly washed, presented the appearance shown on page 221. Here we will leave them until next month, when we shall follow Mr. Cantoni in his further demonstration, which will show an armature for the protection of the legs, the wiring of the fingers, the throwing of the plaster, the rocking, the chipping out, and the final resurrection, as it were, in plaster, of the student's clay model which we have seen so ruthlessly destroyed.
Casting in Plaster: a Demonstration.
Trimming the edges of the front mould before making the back mould, which will have to be made in three pieces.
(To be concluded)
Casting in Plaster: A Demonstration.
Making the back mould - starting from the base. The photograph shows, at A, the extra piece made to protect the hand. The upper part of the mould has now to be added.
Never think of shadows as shadows, or you will make them too dull. Think of them as colour. Around the eyes the colour of the shadow will be somewhat yellow, because the surface upon which the shadow falls is yellow. Around the nose the shadow will certainly be somewhat red, because there is red in both cheek and nose.