The Decoration of Leather Part 2

Leather decorated entirely by means of punches is called hammered leather.

It is used in the style of decoration described later under the name of modelled leather with punched background, and can also be employed with great advantage in conjunction with carved leather.

[Ill.u.s.tration: 4. CASKET COVERED WITH EMBOSSED LEATHER, _CUIR BOUILLI_.

FRENCH, EARLY 15TH CENTURY.]

MODELLED LEATHER

Leather may be modelled in two ways; with a cut outline or with the traced outline merely accentuated with the tracing-point or opener. In the former case the leather must be fairly thick, in the latter it may be thin calf or Russia, which is very soft and delicate.

[Ill.u.s.tration: FIG. 12.--LOWERING THE OUTER EDGE WITH A MODELLER]

Leather modelled after being cut should, when finished, have the appearance, with regard to the relief, of a metal or modelled wax plaque.

The leather takes the desired shape easily, and should therefore be delicately handled.

The great charm of modelled leather lies in the softness of its forms, and care must be taken to avoid irregularly cut outlines which disagreeably arrest the eye by failing to merge into the ground.

Faulty incisions, or those too deeply cut, are liable to leave a light line between the modelled subject and the background, due to the cut having exposed not only the surface, but the inner substance of the leather. This light line will also have a tendency to appear if the modelling is not done directly after the opening of the lines, or if they are too widely opened, or if the opener is too sharp and unduly deepens the cut. The fault can be remedied by staining the line to match the surface of the leather.

MODELLING TOOLS

The tools used for modelling are not numerous; two or three modellers, more or less fine and of different curves, (Fig. 12) are sufficient. A special tool, called _Pied de Biche_ (hind's foot) in allusion to its shape, is also useful in depressing the ground at right angles to the modelling. Modellers may be either of nickelled steel or of bra.s.s, provided that the convex side with which the leather is modelled be perfectly smooth. It is better not to use ordinary steel which, when the leather is wet, might cause it to become stained through the rusting of the tool occasioned by the materials used in tanning. It may also be mentioned here that when using acids for _patine_,[5] steel tools should be kept away from the work. Hydrochloric acid in particular will rust them so badly in a single night as to make them unusable unless they are repolished.

[5] See note to page 64.

EMBOSSING LEATHER

When the leather is thick it must be thoroughly wetted on both sides; it is then taken in the left hand, the portion to be embossed being between the forefinger and thumb, which are laid flat on the surface of the leather, while the other three fingers form the under part of this species of clamp, and ensure the leather remaining steady (Fig. 14). Steel clamps are made for fixing the end of the leather to the table, but the system of holding it in the hand is preferable, except for very large work, as it can be more readily moved about.

[Ill.u.s.tration: FIG. 13.--BALL-SHAPED STEEL TOOL WITH HANDLE FIG.

14.--POSITION OF HANDS IN EMBOSSING LEATHER]

A modeller or a tool consisting of a small steel ball with a handle (Fig.

13) is then worked backwards and forwards with more or less pressure on the back of the leather until the desired degree of relief is obtained. It is possible to work very high relief by this method.

Another way of embossing in high relief, which we believe to be here described for the first time, is as follows: The outline of the design must first be traced on the flesh side of the leather. This is done by placing blue transfer paper under the leather, with the blue side uppermost, while the design is being transferred to the surface of the leather with the tracing-point in the manner described on p. 20. A chamois leather bag, about 16 12 inches in size, is filled with very fine, carefully sifted sand, and then sewn up as tightly as possible, so that the surface is quite taut. The bag is placed on the table, and the leather face downwards upon it. The steel ball is then rubbed to and fro, on the flesh side of the leather, at the point to be embossed, and the relief is produced as the sand yields under the pressure of the tool. The sand gives enough support to the leather, however, to prevent it stretching too much, as it would be liable to do if merely extended over a frame.

The next process is to open the incisions. This is not done till after the leather has been embossed in order not to further impair the strength of the leather at the outline, already diminished to some extent by cutting.

The object of opening the incision is to facilitate the flattening of the outer edge so that it merges into the ground and the graduated modelling of the inner edge to form the softened outline of the ornament in relief.

[Ill.u.s.tration: 5. CASE OF CUT AND EMBOSSED LEATHER, _CUIR BOUILLI_.

ITALIAN, 15TH CENTURY.]

To obtain this soft effect, the modeller is gently pa.s.sed from left to right over the angle formed by the inner edge of the incision and the surface of the modelling. The tool may be lifted and the leather turned about to place it in the right position for this movement. The leather is frequently wetted (but not to such a degree, however, that the water oozes out of the surface when the modeller is used), and a.s.sumes the substance of wax. Should it show a tendency to rise after it has been depressed, it must be gone over again with the tool; if the leather is of good quality, it will keep the modelling permanently when it is once dry.

Care must be taken to avoid making a false impression; the least contact of the tool with the leather will leave a mark on the damp surface, which it is not always possible to efface from beneath.

Having dealt with cut and modelled leather, we now turn to modelling without cutting, the outline of the design being first simply marked out with the tracing-point, or with the opener held very slanting to avoid wrinkling the surface of the skin. This process should be adopted in preference to the preceding one, for comparatively thin skins which would not bear cutting. The relief may be obtained in the manner described above by working it up from the back of the leather, or the leather may be laid surface upwards on a cake of wax and the design brought out in low relief by depressing the background with the tool. Better results are obtained with the latter method. The wax is applied under the parts to be modelled, which must be accurately marked out for this purpose on the under side of the leather, and thin paper is pasted underneath it to keep it in place and prevent it sticking to the table; or a very smooth, thin tablet of wax is placed on stout cardboard under the entire piece of leather; when in position, the edges of the leather should be turned over and firmly fixed underneath the cardboard in such a manner as to prevent the wax forcing itself out under the pressure of the tool. The wax must be prepared with spirit to expel the grease or contact with it would stain the leather.

After thoroughly wetting the leather, the outline should be well accentuated with the opener and the design brought out by lowering the ground all round it with a fine modeller. The modelling is then done by working the tool with varying pressure and is held in place by the wax.

[Ill.u.s.tration: FIG. 15.--TOOL FOR WORKING REED DECORATION]

Beginners are advised to start by copying a plaster cast, in order to get a full understanding of the values of relief.

The subject of wax supports brings us to that of padding the relief to preserve its form, which may be done in many different materials. The padding may be made of a special wax treated like cement, or of absorbent cotton-wool soaked in a paste made of flour and water, or of cuttings of glove skins shredded very fine[6] and mixed dry with talc, flour, dextrine, etc., forming a liquid paste when water is added which can easily be run into the hollows of the relief. This paste solidifies rapidly, and is not affected by damp. Cardboard or cork sc.r.a.ped very fine and mixed with paste or flour and water will also form a durable padding.

A special padding made with a round cotton cord dipped in flour mixed with cold water is employed for flower stems and the so-called reed decoration--a decoration consisting of a round line in relief of uniform width, which lends itself to many combinations, and is worked with the tool ill.u.s.trated in Fig. 15. It may also be used in modelling the relief by pasting it first on the back of the leather and, when dry, moulding the leather with a modeller over the projection on the surface caused by its thickness.

[6] _Dollage de gants._

MODELLED LEATHER WITH PUNCHED BACKGROUND

When the leather has been cut before being modelled, the punch completes the work of the modeller in sinking the outer edge of the incision into the background. To do this perfectly, the edge of the punch must be placed very exactly against the outline of the raised design; the handle should be held slanting slightly to the left in working; extra pressure will thus fall towards the right on that part which, in spite of having been sunk by the modeller, will always show a tendency to rise if the punch be used too flat upon the surface.

A hammer, though useful in working certain punches which depend upon being deeply impressed to produce a good effect, requires great sureness of hand when used as described above, to prevent overstepping the limits of the outline, and punches in wooden handles are much to be preferred for this work. Too deep an impression is avoided by their use, and, by guiding the end of the punch with the left hand, it can be placed more surely in the right position and worked by the steady pressure of the wrist. (Fig. 16.)

The most useful punches are those producing a powdered or a very small check pattern. With these there is no need for the impressions to be arranged in any regular order; it is indeed better that they should slightly overlap so that no part of the ground is left out. The effect of some punches is dependent on their arrangement in combination; others can be arranged independently to form a _semis_--a pattern made up by the repet.i.tion of some given figure at intervals.

Wheels, either plain or having a more or less broad surface engraved with any kind of pattern (such as a check diaper, pearling or arabesques), are used for outlining or for continuous patterns, or for producing imitations of s.h.a.greened leather.

An excellent effect can be obtained by varnishing the parts depressed by the punch to make the colour adhere, and then painting them with _gouache_ or bronzes. By rubbing the leather afterwards with a woollen cloth, the colour or bronze is easily removed from the unvarnished modelling.

PYROGRAVURE

[Ill.u.s.tration: FIG. 16.--USING A HAND PUNCH]

The tools employed in pyrogravure are based on the same principle as the instrument for thermo-cautery in surgery. The apparatus in most general use consists of a platinum point mounted in a hollow metal handle connected by a rubber tube with a pear-shaped rubber blower. This blower serves to inject through a tube the carburetted air from a small benzine reservoir attached to it. The incandescence of the point is maintained by this constant injection, and the lines are burnt more or less deeply according to the degree of incandescence, and the pressure applied. The great difficulty is to keep the line of even thickness throughout. The points are to be had of different shapes according to the effect desired.

Some are pierced at the end, so that the carburetted air escaping leaves a mark on the leather similar to that which would be produced by a hot iron grazing its surface. In this way a brown tint is obtained varying in darkness in proportion to the proximity of the point to the leather.

[Ill.u.s.tration: 6. BLIND-STAMPED MOROCCO BINDING WITH GILT ROUNDELS AND COLOURED CAMEO DESIGN. _CELSUS._ _DE MEDICINA._ _VENICE_, 1477. ITALIAN, 15TH CENTURY.]

There are also rather large blowers which are worked automatically by compressed air, while others have a pedal action like a sewing machine.

It would be difficult to explain the many ways of handling the point so as to obtain different effects; it should, however, always be held slightly inclined to the right. It is shaped like an eagle's beak, so that by using the point alone, fine lines of more or less depth are obtained, and by inclining it more to the right the rounded part will burn a larger surface of the leather. Very deep hollows can be made with the point highly heated. Pyrogravure is also an efficient way of depressing the ground work of thick leather when the point is worked with repeated touches over the surface. With a light hand and an accurate knowledge of the degree of heat required to produce fine lines, a skilful artist is able to draw with the point as if it were a pen.

The left hand plays a very important part in the process by controlling the injection of carburetted air through the blower, and thereby regulating the heat of the point. When the incandescence is automatically produced, equal facility in varying the degree of heat according to the requirements of the work is not possible.

POINTOGRAVURE

The following description is borrowed from Mons. E. Aumaitre, the inventor of another process for the decoration of leather to which he has given the name of pointogravure.

The implements required are two graving-points, one large and one small, a modeller and a spirit-lamp.

The design having been traced on the leather, the whole of it is wetted with a sponge as described on page 19. The point is then heated in the spirit-lamp and pa.s.sed lightly over the line. It should be held like a pencil and heated sufficiently to produce a light brown mark on the leather, and it should run smoothly without sticking. The fine lines are drawn lightly and the point pressed more heavily for the deeper ones. Deep hollows can be made by sloping the tool, and using its widest side. The point being very small, it requires frequent heating to keep it in a condition to produce satisfactory results. It is not hot enough unless it runs smoothly on the leather and darkens the impression. On the other hand, overheating is to be avoided to prevent burning the surface of the leather. This process skilfully carried out will produce shading, hatching, and lines of great delicacy, also much softer effects than pyrogravure. It lends itself equally well to the broad treatment of a design.