CHAPTER III

LEATHER MOSAIC

Until recently it seemed as if this pleasing art would have to remain the monopoly of a limited number of professional craftsmen working with numerous tools, and reckoning a ten years’ apprenticeship necessary to the attainment of proficiency in their craft. But although there is small likelihood of amateurs entering the domain of the followers and emulators of artists such as John Reynes, Florimond Badier, Monnier, Padeloup and Jubert, Mons. Eugène Aumaître has invented a simpler process of leather mosaic, for which fewer tools are required and which is within the reach of artist and amateur alike. The following pages contain the result of the study of his method, with the addition of some observations based on the practical experience of the author.

LEATHER FOR GROUNDWORK

Any skin may be used for the groundwork of leather mosaic, but morocco, and especially the kind called Cape morocco, is generally preferred, because of the grained surface which shows up the inlaid decoration to the best advantage.

Other skins, however, with either dull or glossy surfaces make good backgrounds for mosaic decoration, and as they are generally fawn coloured, they may first be stained to produce shaded groundwork very attractive in effect.

The old masters of leather mosaic made great use of fawn-coloured calf, occasionally adding a touch of coloured lacquer to bring out the light parts of the design.

PREPARATION OF THE LEATHER FOR THE GROUNDWORK

The first necessity in working leather mosaic is to have a flat and rigid surface to work upon; it is indispensable therefore, when the leather is not in itself sufficiently thick and firm, to stretch it on cardboard. This rather troublesome preparatory process is best confided to an expert; we will, however, describe it for the benefit of those preferring to execute it themselves. A strong, smooth piece of cardboard called millboard is taken, and the edges rubbed down with glass paper. A thin coat of paste is applied on one side of the board and allowed to dry.

[Illustration: FIG. 18.——PARING KNIFE]

[Illustration: FIG. 19.——PARING KNIFE]

The edges of the leather must now be thinned so that they will more readily stick when turned over and pasted under the board, and also to avoid the unevenness which the normal thickness of the leather would produce underneath. A paring-knife with a broad, flat, very sharp blade (Figs. 18 and 19) is used for this purpose; its manipulation is difficult and requires long practice. The handle is held against the palm of the hand, and the fingers extending over the blade cause it to penetrate the leather superficially by a more or less strong pressure, the object being to take off shavings from the back of the skin, increasing towards the edge until the edge itself is reduced to the thickness of a cigarette paper.

[Illustration: FIG. 20.——PARING LEATHER]

The leather is placed surface downwards on a lithographic stone or a slab of marble. It is held stretched with the left hand, the fingers being extended over it on the face of the stone, and the thumb pressed against the side leaving the part just in front of the fingers free to be pared (Fig. 20). It is of the first importance for the success of this operation that the leather should be kept well stretched. The knife is held almost horizontally to avoid cutting into the leather at too sharp an angle, and is worked from left to right towards the edge.

The leather is then fastened to the cardboard by pasting either the whole of it or only the edges, which are turned underneath. In any case ordinary paste should be used; seccotine or glue would sink into and harden the leather, making the subsequent outlining process difficult.

When the piece of leather is so large that it would cause the board to warp when it dries, some paper should be pasted on the other side of the board, which will keep it flat by drawing it in the opposite direction.

[Illustration: 8. BROWN LEATHER BINDING, CUT AND ENGRAVED, WITH PUNCHED BACKGROUND. _GERMAN MS. CHRONICLE OF EVENTS._ GERMAN, 15TH CENTURY.]

The work is then put into the press or under heavy boards. It is important that this should always be done after paste has been used. When it is too large to put into a copying-press, it should be laid upon a flat table and a sheet of nickelled or very smooth zinc placed against the part to be decorated. The cardboard known as _Carton Jacquart_ may be substituted for the zinc, but there is a risk that the moisture of the paste penetrating the leather may cause it to swell, notwithstanding its glaze. The zinc plate or the board should not be smaller than the leather, for in that case the pressure would produce a ridge round its edge.

The groundwork is ready to receive the ornament as soon as it is dry. The different methods of working mosaic will now be explained in turn.

MONOCHROME MOSAIC ON CALF

In this style of decoration the leather used for the inlaid design is white or very light in tone, and may be dyed subsequently to present the appearance of a mosaic made of variously coloured leathers.

LEATHER FOR INLAYING

The skins sold for this purpose are split sheepskins. Their extreme thinness renders them liable to stretch a great deal, and therefore they are most difficult to cut out in any desired shape. To obviate this difficulty, the back of the leather is pasted over, and it is then stretched on a board and fastened with drawing-pins to prevent it from shrinking as it dries. But there is another and a better method——that of mounting the leather on paper.

MOUNTING THE LEATHER ON PAPER

Some paste is made of very light and smooth flour, diluted with half the quantity of water and beaten to a cream. The water is added in small quantities while the mixture is being stirred. Canson paper, or some other strong drawing paper, is pasted over the whole surface of the leather, so that it adheres lightly, and can be removed afterwards without difficulty; it is then placed under boards and allowed to dry thoroughly.

TRACING THE DESIGN ON THE PAPER

The design is traced by means of carbon paper on the paper lining of the inlay leather. A hard pencil should be used in order to produce very sharp lines.

CUTTING OUT THE DESIGN

Cutting-out knives should possess a keen edge and a small blade, and should be so shaped that they can be turned freely in any direction. The knife illustrated in Fig. 21 combines all these qualities. It consists of a very fine double-edged blade, set loosely into a slit in a hard wood handle and secured with a few turns of thread; a piece of leather over the whole (A) keeps the blade in its place. The handle being loose, it is possible to give any minute movement to the blade, which can also be taken out for sharpening when necessary. It must be kept as sharp as a razor. The extreme fineness of this blade facilitates cutting out the delicate parts of a design, but if handled too vigorously it is apt to get out of shape. The second tool (Fig. 22) is a stencil-cutter’s knife, and is very similar to the one described above except in size. It is usually sold mounted in an ebony slide bound round with copper wire, but can with advantage be mounted as in Fig. 21, in a split hard-wood handle.

One little known tool deserves mention for its flexibility and lightness. This is a small scraper shaped like an unslit pen, the blade widening from the point in two very fine edges like the head of a pike. It is used by photographers and miniature painters, and is sold by the dozen in small boxes. When in use it is firmly fixed in a small pen-holder so that it does not turn when pressed upon (Fig. 23).

[Illustration: CUTTING-OUT KNIVES: (A), FIG. 21, FIG. 22, FIG. 23]

The special knife illustrated in Fig. 17 is sometimes recommended, but it is better adapted to cutting out thick skins for open-work decoration, as the point of the blade is not sufficiently fine for use on thin leather.

[Illustration: FIG. 24.——CUTTING OUT INLAY]

The leather to be cut out is placed on a sheet of the cardboard used in mounting drawings, which is firm, but at the same time easily penetrated by the point of the tool. The nature of the board on which the leather is laid is important, for to ensure a clean cut, the tool, as it pierces the leather, must not encounter a veined surface such as that of wood, which might deflect the point. The three middle fingers of the left hand hold the leather mounted on the paper upon the board, the thumb and little finger supporting the whole underneath (Fig. 24). The part which is to be cut is turned towards the knife by the left hand, the right hand being held in a fixed position with the knife, slightly inclined to the right, cutting the leather as it is presented by the other hand. The lines must be cleanly cut in order that the subsequent operation of outlining may be successfully accomplished. With every care in cutting out, it may sometimes be found in detaching the cut portion that a small thread of the leather remains unsevered. In this case it should be neatly cut through, and on no account may it be pulled to make it give way, which would result in spoiling the design by either tearing or stretching the leather. When cutting out a design on a large scale it is not possible to hold the work in the manner just described; a part of the design to be cut out is therefore placed flat on a large sheet of cardboard on a smooth table and can then be turned about as required under the point of the knife.

[Illustration: 9. COVER OF CASE FOR A CUP IN WOOD COVERED WITH LEATHER, _CUIR BOUILLI_, EMBOSSED, PAINTED AND GILT. ITALIAN, ABOUT 1500.]

When the inlay is of white or very light leather, it is extremely difficult to conceal any joins occurring in the middle of lines; care must therefore be taken that there are as few joins as possible, and that they are arranged at points where they will easily disappear in lines of the design going in an opposite direction.

The centre of the design should be cut out first, and then the outer lines, reserving the more delicate parts, such as flower stems, for the last.

PASTING THE INLAY ON THE GROUNDWORK

When the inlay is of a nature that does not require placing in any very exact position, as for instance a spray of flowers, it will be sufficient to lay it on the groundwork and mark the principal points. When it is to occupy a definite position, forming the framework of a design, for instance, it is laid upon the groundwork exactly in the right place and then given a sharp turn in a copying-press, great care being taken that it does not get displaced during the operation. Owing to the thickness of the supporting paper, this will be sufficient to mark the outline of the design on the groundwork. Some very smooth starch paste is then applied with a flat brush on the exposed side of the cut out leather, care being taken that every part, however small, is thoroughly pasted. To facilitate this and to prevent the leather curling up when pasted, it should first be fixed to a board with drawing-pins.

The portion of the ground which is to receive the inlay is damped with a soft sponge; the inlay is then placed in position and pressed down with the palm of the hand, a modeller being used for the finer parts. If it should become displaced, the greatest care must be used in correcting it. With the small pincers used by artificial flower-makers, the minutest pieces of leather can be taken up and replaced after being repasted, if necessary.

SETTING IN THE INLAY

The next process is that of setting the inlay into the groundwork, so that no relief remains. This is done with the help of a roller with a long wooden handle held in both hands and pressed against the shoulder, as illustrated in Fig. 25. The paper on which the inlay is pasted plays an important part in this operation; the greater its thickness, the greater will be the pressure attainable, and the deeper the penetration of the inlay into the damp background.

At first the roller is worked lightly with one hand only to ensure the uniform adherence of the inlay, the movements being short, and repeated several times over the same spot. When afterwards pressing heavily over the whole surface, a piece of thin, tough paper between the roller and the work will prevent the inlay from curling up, and the paper may be lifted from time to time to see that nothing is out of place.

[Illustration: FIG. 25.——USING ROLLER TO SECURE ADHESION OF INLAY]

When the work is not too large, it is easier and more effectual to use a copying-press instead of a roller for this operation, which is then carried out in the following manner: A piece of felt is laid in the press, and over it a sheet of very smooth or nickelled zinc, or, failing this, of _Carton Jacquart_. The work is then laid on it and covered with a second sheet of nickelled zinc and some pasteboards. The press is screwed up as tightly as possible.

The work must not remain in the press, as if allowed to dry completely, the subsequent removal of the paper pasted to the inlay would become extremely difficult. To effect this removal, the paper is dabbed with a damp sponge until it is ready to come off. A point of the pincers is inserted underneath the paper which, if sufficiently soaked, should easily come away when the tool is slid gently along. The paper, as it becomes freed, should frequently be cut off with scissors to facilitate the handling of the tool. The leather, being damp, may possibly become unstuck and stretched during this process. It must then immediately be repasted and replaced, and the stretched part reduced to its original size by gently pushing it together with the modeller. Should it be found impossible to reduce it thus, the part that is out of shape must be cut off and joined on again. When the paper has been removed, the whole surface is carefully washed over, wetting it as little as possible, so as not to cause the mosaic to become unstuck. The work is then placed in the press, or under boards, until it is perfectly dry.

OUTLINING THE MOSAIC

Outlining is the most delicate process in leather mosaic. When well carried out it should be impossible to distinguish the line where the inlay joins the groundwork. The extreme edge of the inlaid leather is pressed into the groundwork by means of a tool invented by Mons. Aumaître, producing a fine line the breadth of the edge of the tool selected. This tool, called an outliner (Fig. 27), has two blunt ends, one rounded and the other square, and is flat on one side and rounded on the other. The rounded side of the tool affords extra pressure, and should therefore be placed on the inner side of the line so that it serves to increase the depression of the edge of the inlay. It is best to work the outline with the cold tool first, and then to go over it again with the tool heated. The inlay is lightly damped round the edges, and the round end of the tool is placed half on the inlay and half on the groundwork. The tool is held first inclined backwards (as in Fig. 26) and then brought with pressure to a perpendicular position (Fig. 27). This will make a groove into which the edge of the inlay will disappear. The square end of the tool is used for straight lines. Great care must be taken in placing the tool correctly; no portion of the inlay may protrude beyond the flat side of the tool, as any particle of the edge, however minute, which is not sunk in the groove would have to be cut off. If the edge of the inlay does not extend up to the tool, the error is still more troublesome to correct, more particularly when the leather is of a delicate colour, on account of the difficulty of matching the exact shade for joining it.

[Illustration: FIG. 26.——FIRST POSITION OF OUTLINING TOOL]

[Illustration: FIG. 27.——SECOND POSITION OF OUTLINING TOOL]

After this operation the edge of the outlining tool (Fig. 28) is inserted in the groove thus formed, and worked with a short up and down movement. A ruler will serve as a guide in working straight lines. The round side of the tool is held slightly inclined towards the edge of the inlay. The wheel illustrated in Fig. 29 may also be used, but requires great sureness of hand for its successful manipulation. Gouge-shaped outlining tools with curves of different degrees (Fig. 30) are useful for little curved lines which are otherwise difficult to work; also the tool represented in Fig. 31, for the lettering on bookbindings, etc., where the lines require to be sharply finished. It must, however, rest with the artist to select the tools he considers most suitable for his work.

[Illustration: FIG. 28.——GOUGE OUTLINER.

FIG. 29.——OUTLINING WHEEL.

FIG. 30.——GOUGE OUTLINER.

FIG. 31.——STRAIGHT OUTLINER.]

When the outline has been worked with the cold tool, a hot one is used to go over it again to ensure perfect adhesion, and to give an attractive brown tint to the lines. The end of the outliner is heated over a spirit-lamp to a degree at which it can still be comfortably held in the hand, and used as before. If the tool does not run smoothly, owing to the elasticity of the edge of the inlaid leather, the latter may be lightly damped with a brush. It will at first be found difficult to keep the tool at the right heat. As a groundwork, calf with a smooth surface is more sensitive to damage from an over-heated tool than split sheepskin. It is useful to paste some of the inlay leather upon a spare piece of the leather of the groundwork, with which to test the heat of the tool. If the tool be too hot, it will burn and penetrate the leather without pressure. It can be cooled to the desired temperature on a wet sponge.

The next process in leather mosaic is that of colouring, which is dealt with in