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 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.
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.
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 Chapter IV. It then only remains to give the finishing touch to the work by passing a polishing iron (Fig. 32) over the surface, to polish it and make it perfectly even. The tool is heated by holding the part which does not come in contact with the leather over the flame of a spirit-lamp. The polished side should frequently be well rubbed on flannel, and should any portion of its surface become dull, the polish can be restored with fine emery paper. The polishing iron, when heated, is held in the right hand and worked with little stroking movements, bringing first the end and then, by lowering the handle, the back of its polished surface in contact with the leather. The various positions of the tool during this operation closely resemble those of a vessel when it is pitching.
This style of decoration consists of different coloured leathers arranged upon a ground, and is the only one that can properly be called leather mosaic. The work of marking it out is a lengthy one and demands scrupulous exactitude. A finished design is first painted in water-colours and marked with letters which are repeated on the pieces of coloured leather, so that the exact place is indicated which they are to occupy in the design. It is important in this style of mosaic to obtain a very correct tracing of the design on the groundwork. On a smooth and light ground the tracing-point lightly worked will be sufficient; when the ground is dark or has a grained surface, red or white transfer paper should be used. The most satisfactory method of marking the design is by impressing a stencil of thick paper, but it cannot be employed with morocco leather for fear of crushing the grain too much. A thick stencil, however, carefully used without exerting great pressure, may give a sufficient result without spoiling the grain.
For polychrome mosaic on a smooth ground with an inlay of split sheepskin pasted on Canson paper, the method already described for working mosaic of one colour is the best, but at the same time the directions which are given below for placing the differently coloured skins side by side in position should be followed.
Morocco leather for inlaying is thinned with the paring-knife, but it cannot be reduced to the excessive thinness of split sheepskin. It possesses, however, the advantage that the extreme edges may be made thinner in proportion for laying one over the other at the point where they meet.
After it is pared, the back of the leather is pasted over and it is pinned out on a board to dry. The different parts of the design to be inlaid are then traced on the various coloured leathers, and cut out in the manner already explained. The difficulty of placing the pieces exactly edge to edge is so great that it is better to allow them to overlap very slightly, but in order that this should not produce undue thickness at the point where they join, the substance of the extreme edges must be further reduced with the paring-knife. A small margin is left for this purpose in cutting out. Paring the edges to their thinnest possible substance will give a slightly jagged outline, and the extra piece will thus more easily merge into the join than if sharply cut. Outlining with the hot tool will perfect the join.
To avoid crushing the grain of rough morocco, the tool illustrated in Fig. 33 is used instead of the roller to secure the adhesion of the inlay to the groundwork, in order that the pressure may be applied only upon the inlay. Damping the groundwork, except where the ornament is placed, should be avoided. The tool is held pressed down with both hands as in Fig. 34, and rubbed backwards and forwards. The work is then placed under boards.
The remarks on paring leather for polychrome mosaic apply also to paring the leather for covering a design in relief. An extra margin is left round the edges, which are “slashed” with the tool, so that they may better embrace the form of the modelling, the finer details of which are not worked until afterwards. The leather is first placed dry in position over the modelling, and smoothed over with a modeller, so that it takes the form of the relief. It will then be seen how much should be cut from the edges, so that it may exactly fit into the outline when it is pasted on.
This method of mosaic invented by Mons. Aumaître possesses the advantage of being very durable, owing to the edges of the inlay being secured between the two edges of the incision made in the groundwork. The outline is deeply cut in the groundwork, the incision well opened with the opener and then filled with paste. The inlay is also pasted and the edges inserted in the incision. A wheel or a large modeller is used to press down the edges, and the outline is then gone over with a hot tool.
The term mosaic is perhaps not very correctly applied to this style of decoration, in which the shape of the design is indented, by pressure, on the damp surface of the groundwork, and filled in with an inlay of leathers thick enough to stand out in relief, and be subsequently carved. A thin kind of cowhide[8] specially prepared for embossed work is used. The design is traced upon it in the manner described for carved leather, and a preliminary modelling is executed indicating the outlines and veinings as strongly as possible. The high reliefs may be embossed and lightly stuffed. This done, it is placed upon Bristol board, not less than half the thickness of the leather itself, with a piece of red transfer paper face downwards in between. The whole is firmly fixed upon a drawing board so that nothing can get displaced, and the design is cut out with a stencil-cutter’s knife (Fig. 22). If possible, both leather and Bristol board should be cut through at the same time, but should the knife not penetrate the latter sufficiently to cut it through, the outline will have been marked on it by the transfer paper and it may be cut out separately. The leather and the board must, however, be absolutely identical in shape and very sharply cut. With the die thus formed by the Bristol board, the morocco groundwork is depressed to receive the inlay. It is thoroughly wetted and the water allowed to sink in. The board is then placed in the exact position which the leather inlay is to occupy, and covered with a very thick sheet of blotting-paper to protect the grain of the groundwork from being crushed too much. The whole is well pressed in the copying-press until the die has sufficiently entered into the leather. The leather inlay should then be tried in the hollow thus produced, and trimmed where necessary if it be too large. After pasting it thoroughly, taking care not to omit any small points, it is placed in position on the groundwork and worked into the hollow with a modeller. The work is then placed under boards to dry; a press would flatten the relief too much.
[8] Kip-skins.
When the paste is quite dry and the leather well stuck, the carving may be proceeded with as described in Chapter II.
Very characteristic effects are obtained by colouring leather worked in this manner.
The following description of a style of decoration, called by Mons. Belleville “incrusted mosaic,”[9] is derived from the valuable work of that author, entitled Le Cuir dans la Décoration Moderne.
[9] Mosaïque par Incrustation.
In incrusted mosaic the design is not cut out and applied on the background, but the different pieces of coloured leather forming the design and the leather of the background are placed side by side on the same plane. When the ornament is simple and the background plain, the design is traced on the groundwork, carefully cut out, and used as a pattern for cutting out the piece destined to replace it; when the ornament is to embrace the whole surface, the following method is recommended: The design, drawn on paper and coloured, is fixed on a drawing-board and over it is placed a sheet of transparent paper, or some thin muslin carefully sized and stretched. An exact tracing of the design is made on rather stiff paper, which is coloured or numbered to correspond with the pieces of the different leathers which are to compose the mosaic. The tracing is then cut out, separated, and the pieces pasted on the corresponding leather, either with the face on the flesh side of the leather, or the back on its surface. In the latter case it is very lightly done, but if pasted on the flesh side it should be done securely, as it will remain permanently. When all these pieces are cut out of the leather they are pasted in their respective places on the design, and the whole put in the press for about ten hours. If the work has been well executed, the lines where the pieces of leather come together will be hardly visible; the next step is to accentuate them and make them regular. This may be done either with a heated wheel giving a smooth even line, which may, if desired, be subsequently gilded, or by pyrogravure. Vigour and character can be imparted to the outline by the use of the latter process, and the darkened colour of the burnt line is made more brilliant by polishing it with an agate burnisher. In either case the tool must be worked accurately with its edge half on each side of the line. The main advantage of the process of incrusted mosaic is that the grain of the leather employed is better displayed than in inlaid mosaic. It is only suitable for work on a large scale.
[10] Patine represents a veneer, or wash of colour, applied on the surface, or in the hollows of leather, to intensify its tone, or to give artificial effects, such as those of verdigris, rust, or antiquity.
Partly owing to its nature, and partly owing to the tanning process, leather is susceptible to the action of the dyes used to colour it in degrees varying according to their composition and penetration. We will not attempt to enumerate all the dyes that may be employed or to describe their composition. Excellent results can be obtained with ready made preparations, and some brief remarks on the subject are all that is necessary for the purpose of this work.
Practical experience alone is a reliable guide in the selection of dyes, as, whatever their base may be, they all vary greatly in use. It may be remarked that there are many aniline dyes which are more durable than vegetable ones, although there are others which merit their reputation for instability. The colour of dyed leather cannot be expected to remain unaffected by constant exposure to direct sunlight, but it should not alter with ordinary use.[11]
[11] See the remarks on Leather for Bookbinding in the Note at the end of this volume.
It is obvious that, in proportion as the colours sink into the leather, they will lose in brilliancy, but on the other hand, this very absorption, which allows colours to be superposed and appear translucent, gives a depth rarely obtainable in materials of less capillarity.
The following notes are intended merely as a general indication of the manner of treating the various substances used in colouring leather.
The substance sold by druggists under the name of potassium is very violent in its action and would burn the leather as well as the brushes used to apply it. It should only be employed, and that very sparingly, for such purposes as black lettering. Pearl-ash should be used in preference, but also with great caution, or it will not only destroy the surface, but rot the substance of the leather.
Potash is soluble in water to saturation point, that is to say, a given quantity of water will not dissolve more than a given quantity of potash.
It is very difficult to measure the exact strength to use; that which is barely sufficient to penetrate and colour a surface artificially made smooth by rolling, will sink in where the leather has been cut or punched and immediately darken it considerably. It is a good plan therefore to experiment on a spare piece of the leather. Potash lye is more easily used in the right proportion, and may be employed for staining very light coloured leather.
Soda has the same effect as potash, except that it is a little less strong; both substances have always been much employed in dyeing skins. Permanganate of potash is supposed to dye a mouse-grey colour, but it is most uncertain in its action, as it depends entirely on the porosity of the leather. Xanthin and catechol browns are pleasing in appearance, but their effect is less rich than that obtained with potash. They become improved by hard rubbing with encaustic.
Sulphate of iron has a strong and persistent odour and is also somewhat injurious. It is useful, however, and produces a colour varying from a light shade to an intense violet black. When used over potash, a dead black is obtained.
Alizarin, the colouring principle of madder, which can also be obtained from coal-tar, is employed in many colour combinations and gives a fine durable red. Hydrochloric acid changes it to violet. Carthamine and cochineal also produce good reds; the latter is turned orange by the action of hydrochloric acid.
Hydrochloric acid turns ammoniacal cochineal pink, but merely discolours the red made from archil. Direct extracts of red wood are unaffected by it.
The colouring matter of logwood, extracted by treating the powder obtained from an aqueous decoction of the wood with spirit, is sold as hematoxylin. Metallic salts convert it to a violet black, salts of tin change it to pink, alkalis to blue, and acids to yellow. Durable pinks are obtained directly from carthamine, the colouring matter of Carthamus Tinctorius.
The base of most fine yellows is picric acid. The chromates of zinc and baryta give very permanent yellows, which are particularly useful in mixing greens.
The vegetable yellows are less durable. They include turmeric, which is especially fugitive, and quercitron; the former is turned red, and the latter brown, by the action of hydrochloric acid.
Orange tints are easily obtained by using red over yellow, first allowing the yellow to dry completely; or they can be bought ready prepared with alizarin. Mandarine and nasturtium tints can also be bought ready prepared, or may be made by a mixture of vegetable colour, such as saffron and arnotto.
Good and durable blues are obtained from indigo and alizarin.
Greens of every composition are fugitive, especially those sold ready mixed. Better results are obtained by applying yellow and blue one over the other than by the direct application of the colour, but when the range of tints thus afforded is too restricted, recourse must be had to some of the numerous dyes varying in tint from greenish yellow to deep olive. Successive applications of sulphate of iron and picric yellow will produce the latter colour, and a vegetable green, which, however, is not very durable, is made from buckthorn berries.
All the dyes which have been just enumerated, which form, however, but a very small proportion of those in existence, are employed in dyeing textiles. These materials have first to be treated with mordants such as tannin, chrome or sumach, in order that they may take the dye, whereas leather is already prepared to receive it by the tanning process.
Ordinary water-colours based on glycerine or albumen can be used in the decoration of leather, but are recommended only for colouring small parts of a design, partly because liquid colour is more easily applied over large surfaces, and partly because, being less transparent, they do not lend themselves to the process of rubbing which plays so important a part in patine. Oil or spirit colours, on the other hand, possess a transparency which allows of their being used over a ground coloured with a different medium. When the leather on which they are painted is undyed it should first receive a coat of paste.
Colours sold under the name of patines grasses will produce a groundwork of great brilliancy, if well rubbed before they are quite dry.
The use of gouache should be limited to the hollow parts of incised or punched leather.
Gold and bronzes are also used with good effect.
Colours obtained from potash and sulphate of iron—dark green, dull red, etc.—are much used for groundwork. Potash produces a warm brownish-red, and tints, varying in colour from a pale to a dark slate grey, are obtained with sulphate of iron. As already stated, a coating of picric yellow over the latter will give a dull green.
In colouring large surfaces, it is best to use soft sponges, or small pads of cotton-wool covered with soft linen. The pads can be held by the edges of the linen and the sponges may be mounted on handles, but the best protection for the hands against staining is a pair of very soft rubber gloves like those used by surgeons.
The leather is first damped all over and the colour then applied in a succession of even washes. Care must be taken not to unduly darken any part of the leather by using too much colour, bearing in mind that different parts of the skin will vary greatly in porosity. In colouring groundwork with various superposed tints, the actual results are often entirely different from those one has had reason to expect. So far as is possible, in order to prevent this from happening, it is advisable not to mix the colours of different makers on the same piece of work without knowing their composition, or first experimenting with them on a spare piece of the leather.
A second colour should never be added until the underneath one is dry, or a muddy effect will result. If the colour becomes too dark, or if the second stain predominates unduly instead of merging into the underneath one, the whole work, fixed firmly on a board, should be dipped in water and scrubbed with a very soft brush and some soft soap. It should then be allowed to dry in the sun. This method of making the colour lighter can only be used when the ornament is not in relief; it has been found particularly successful in treating potash and sulphate dyes.
Ox-hide, light or fawn-coloured calf, pigskin and white morocco are leathers suitable for colouring. They are, however, very absorbent, and will require an application of paste before staining. This will also be found indispensable in colouring the white split sheepskins used in mosaic.
In staining leather for mosaic, several successive applications of colour will be required, especially in the case of greens which sink in quickly.
In addition to plain dyeing, there are various methods of producing shaded groundwork, marbling, sprinkling, etc.
For shaded groundwork diluted colour is applied with a sponge or pad worked over the leather with a circular movement, and the uniform tint thus obtained is darkened as required by further applications with stronger colour. In shading a ground from one colour to another, as for example from dark olive to malachite green, orange red and pale yellow, the edge of each colour, as it is put on, is covered with a piece of thick paper, which must be firmly held in place, in order to prevent the colours mixing where they come together.
A sponge with large holes is dipped in potash, sulphate of iron, or some other deep coloured dye, and lightly applied over the surface of the leather so that parts of it corresponding to the holes in the sponge are left untouched; or the first application of colour may be made evenly over the leather and the marbling worked, as described, in a second application. Many varieties of pattern can be obtained by moving the sponge in different ways. Leather may be bought ready marbled by a gelatine process.
The leather is first lightly pasted over, and drops of water, more or less large, are scattered upon it by jerking the handle of a small couch-grass whisk full of water against the left wrist held a few inches from the surface of the leather. A very little colour is then taken in the brush and jerked in the same manner over the drops of water, with which it will partially mix and give the effect of roots branching out in all directions. Variety can be obtained by applying the water with a sponge instead of the brush, and the colour in large drops over the whole or certain parts only of the field, or by using dyes of different colours which give curious effects in combining. After applying the dye, the surplus moisture is absorbed with blotting-paper.
The leather may be bleached to a light tint by means of an oil-paint brush dipped in decolorant[12]; the bristles of the brush are pushed back with the finger and when released jerk the acid in fine drops over the surface. The leather must be freshly and thoroughly damped so that the outline of the bleaching shades off into the ground.
Sprinkling is done with a rather close iron grating and a long narrow brush like a plate-brush. The dye is prepared on a flat plate and the brush dipped in it, the superfluous liquid being removed against the edge of the plate. The brush is rubbed backwards and forwards on the grating held horizontally a few inches above the leather over which it scatters a fine shower of the dye. Should the colour froth on the grating, the brush must at once be rubbed upon oiled paper. Sprinkling may also be done with a vaporiser for fixing drawings, but it is difficult to get a sufficiently fine shower so that the drops do not merge into each other.
The above process is a useful one when parts of the leather are to be “reserved,” i.e., to remain untouched by the dye. For this purpose a piece of strong paper is cut to the shape of the part to be reserved and pasted lightly to the leather during the process of sprinkling, after which it is damped and removed. Another method is to paint the reserved parts with one of the two preparations given by Mons. Belleville in Le Cuir dans la Décoration Moderne, afterwards removing it with benzine or petroleum spirit:—“Eighty parts of colophony, 4 of yellow wax, 6 of spermaceti, 4 of tallow, 60 of spirit of turpentine and 10 of alcohol.”
Or, “One hundred parts of virgin wax, and the same of castor oil, with 25 of borax and 25 of copal varnish.”
Instead of reserving the parts of the leather, the dye may be removed subsequently by means of reagents called decolorants. Sulphuric, hydrochloric, oxalic, nitric, or muriatic acid diluted with water in the proportion of one in five, can be used for this purpose, but their effect should first be tried on a spare piece of the leather, as it will vary according to the nature of the dye on which they are used. It should be noticed that, in mixing the acid, the right quantity of water must be measured out and the acid carefully added drop by drop. If water is poured into acid it causes an explosion.
The outline is traced rather deeply on the leather, so that it is still visible after the groundwork has been dyed. When the dye has sunk in, the decolorant can be easily applied with a paint-brush. On modelled leather dyed bronze green, a rag or piece of cotton-wool dipped in decolorant and quickly passed over the relief, will lighten the colour and produce the effect of bronze with the exposed parts rubbed lighter by use. Should the effect of the acid be too strong, the colour may be again deepened by washing the leather over with a yellowish gold stain, which will only take effect on the relief, since it will merge into the darker colour of the rest of the work. The same process may be employed on white calf with a light olive dye to obtain the effect of old ivory. Even when much diluted, however, the action of these acids must in the end be injurious to the leather. They should be used with great care and never undiluted. Where possible, washing the leather over afterwards with water will, to some extent, diminish their harmful effect.
Stencilling is another process by which portions of the leather forming the ornament are reserved from the dye used in colouring the ground. The design is cut out of a very thin sheet of copper or tin. A large short-haired brush[13] is used to take the dye from a plate, or pad, and is then rubbed very lightly over the stencil firmly fixed on the leather. Only the parts unprotected by the stencil will take the colour. The brush must not be too full or the dye would have a tendency to run under the stencil. The most suitable dyes are glycerine inks and marking inks containing nitrate of silver. A variety of colours may be mixed with glycerine for this purpose. The ink thus obtained is transferred to a cloth pad, such as is used by printers, from which the brush will only take the required quantity.
[13] Pompon.
When the leather is dry a lighter tint, transparent enough to allow the stencilled design to be visible through it, may be washed over the whole. Excellent effects of considerable richness can thus be produced. The depth of colour is further increased by the process of rubbing, which is necessary to the proper patine of leather. If done with wax, encaustic or varnish, it is an effective protection for the surface of the leather against deterioration from outside causes. With certain soft leathers, if the colour has not sunk in deeply, rubbing with the finger alone will give it great brilliancy; with other leathers the rubbing will produce an effect in proportion to the degree of porosity of the skin. It should always be done before the colour is dry, but not until it has penetrated sufficiently into the leather not to return to the surface with the pressure. The middle finger is used. A certain amount of polish can be given to the leather by rubbing it only with the finger (moistened with a little oil to allow it to slide easily), or, for a large surface, with the side of the hand instead of the finger. When a medium is used, it is applied with a circular movement by means of flannel or rag; a flannel brush consisting of a series of little flannel rolls, which can be bought at a surgical instrument-maker’s, is very useful for a large surface requiring much rubbing. Pure wax, which must be softened in the hand to make it spread evenly, encaustic and spirit varnish are all efficacious in preserving the colour and increasing its transparency.
Another method giving excellent results consists in applying opaque colour, gouache or bronzes in the hollows of a design and removing the surplus of the colour by rubbing. In this way an incised design can be boldly outlined in light on a dark ground, and may afterwards be bleached within the outlines if desired. After cutting the design on the leather, the whole surface is washed over with potash or any other dark stain, a coat of paste is then applied and immediately wiped off, so that some of it only remains in the hollows. When the paste is dry, some rather liquid gouache is washed over and run into the lines, any remaining on the surface being removed by vigorous rubbing with a damp rag. The same process may be applied to the hollows of punched leather. In using bronzes or gold in powder, some spirit varnish or specially prepared varnish is necessary to make them adhere. After applying the varnish, the surface is wiped over to remove all except that which is deposited in the interstices, and when this is sufficiently dry to hold the powder, the latter is put on with a very soft, short-haired brush and adheres to the varnish. The surface is then rubbed in the manner already described. All powder colours do not mix equally well with varnish; green and blue bronzes often change colour when brought in contact with it. Gold and silver powder give good results, used either dry or mixed with gum on shells. Chinese vermilion may also be employed with varnish, but other colours are more suitable for this purpose when prepared in the form of gouache.
Special manipulation is required for gold leaf applied to the decoration of leather. For gilding over a whole surface, as for instance an aureole round the head of a saint, the following is the best method. Several layers of starch paste are painted with a brush over the part of the leather to be gilded, and followed when dry by a little gelatine paste. A coating of some special preparation is then applied and allowed to dry to the right condition to retain the gold leaf, which varies according to the nature of the preparation; the degree of moisture can be tested with the finger. Gold leaf is sold in small books and is exceedingly thin. A flexible knife, like a palette knife, is used to manipulate it, and a single leaf is laid on a cushion of deerskin stuffed with wadding, and cut to the required size. It is then placed over the preparation on the leather and lightly pressed down with a very soft, round, short-haired brush.
For gilding with hot tools a specially prepared powder made of resin or gum is used. This powder melts with the heat of the tool and causes the gold leaf to adhere to the leather only where it comes in contact with the parts of the tool cut in relief. The process is as follows: Some powder is lightly spread over the part of the leather to be gilded and a piece of gold leaf laid over it, the tool is heated sufficiently to melt the powder without burning the leather and is carefully applied on the right spot, the surplus gold being afterwards removed with the short brush. The tools used by bookbinders are slightly convex, so that firm and even pressure of the whole tool can be exerted by first inclining the handle towards the gilder, and then raising it while still maintaining the pressure and inclining it at the opposite angle.
Gold can also be applied with a brush in the form of powder suspended in liquid gum or spirit varnish. If it does not spread evenly, owing to there being too much liquid in proportion to the powder, dry powder may be added where necessary with a short brush when the liquid is almost dry.
Shell gold is applied with a slightly damped brush and, when dry, may be burnished with an agate or punch; the design of the punch will stand out in bright gold on a ground of dull gold. The pressure of the wrist is sufficient to work the punch and a hammer should not be used.
There is an interesting field for the artist’s enterprise in the discovery of new processes for the decoration of leather by means of colours and bronzes. It is not possible within the limits of a single chapter to give a complete list of the many methods that may be employed.[14]
[14] As a conclusion to this chapter, the French edition quotes from the Bulletin de la Société de l’Encouragement pour l’Industrie Nationale some extracts from the Report of the Committee on Leather for Bookbinding, published by the Society of Arts in London (1901), which will be found in the Note at the end of this volume.
The present chapter is devoted to some remarks on colour combination and the composition of ornament, based on the personal experience of the author.
Three colours, for the groundwork, ornament and high lights respectively, will, in many cases, be found sufficient for a scheme of decoration. A multitude of colours, worked in great detail on a relatively small surface, confuse the eye and hinder it from grasping the effect of the decoration as a whole. Only special styles of decoration, such as Moorish geometrical patterns, allow of the use of a great variety of colours. The circumstance already explained, that in leather decoration dyes may be used one over the other, enables interesting effects to be produced.
A design of sea, with seaweed and fish, can be effectively rendered entirely with sulphate of iron of varying strength. A weak solution is washed evenly over the whole; the waves are then drawn in with a flat brush dipped in a stronger solution, and the dark outlines afterwards bleached with acid where they border the first tint. The fish and seaweed in relief are similarly treated with decolorant, and a light wash of yellow over the whole completes an effective decoration.
The foliage of the chestnut tree in autumn lends itself exceptionally well to decorative treatment, both as regards form and colour. The large variety of greens and yellows are most effective on a ground of brickdust red.
A groundwork of soft grey, brightened by an underwash of very pale yellow, is suitable for reserved or bleached designs. Deep carmine constitutes a rich colour for groundwork, and is produced by using bright red over potash and deepening the effect by rubbing.
In planning a decoration, the artist has generally some special effect in his mind which he wishes to reproduce. It is not unusual, however, for the result to be totally different from what is anticipated, since uncertainty constitutes one of the charms of the art of colouring leather. These failures, as they may be considered from one point of view, often produce interesting effects and sometimes lead to valuable discoveries.
Marbled leather should be decorated with flat ornament only.
Figures in high relief belong properly to the domain of the sculptor and should be avoided in leather work, much of its individuality lying in the value of the outline in producing an effect of relief.
Some skilful artists produce in leather not only the relief, but the turned over edges of petals, etc., and treat twisted ribbons in open-work; the result, though pleasing, is essentially evanescent, owing to the extreme fragility of the detached portions of the leather.
Of all the uses to which leather work may be applied, none offer greater scope to the inspiration of the artist than bookbinding. It has become the fashion not only to provide a more or less rich covering for a beautiful edition, but to suggest in its design the nature of the contents of the volume, should these lend themselves to such treatment. The artist, however, will do well to practise this principle with due restraint, avoiding, on the one hand, what may be called anecdotal design, and, on the other, an over subtle symbolism.
Leather coffers, when well executed, constitute veritable works of art. They present considerable difficulties in the mounting of the leather over the wooden coffer so that the lines of the ornament come exactly in the right place. It is necessary that the lines forming the framework of the design should accurately correspond with the dimensions of the coffer to be covered. A coffer usually consists of a box with a hinged lid; the measure is taken by laying the leather round the whole; the leather is then cut, leaving a small surplus at the edges to be pared and folded over at the sides. The join should be arranged for at the lower border and not at the intersection of the lid and the box. The leather at this point is better left to be cut after it has been stuck on the wood in mounting.
When the leather is decorated in mosaic and consists of panels each enclosed within a patterned border, the probability of its stretching when it is fixed on the wood, must be taken into consideration; Cape morocco, however, if fairly thick will hardly stretch perceptibly.
During the process of outlining the design, which is done before mounting the leather on the wood, it should be stretched to its full extent on a flat board.
When the decoration is in relief, the padding should be very firm, so as to counteract the tendency to stretch during the process of mounting.
Generally speaking, designs based on naturalistic flowers do not give the most satisfactory effects in the decoration of coffers, since the style is not suited to the restricted size of the panels, even when the design ignores them and extends beyond. Designs in the modern style, or Gothic designs in the style of the fifteenth century, or those based on the Arabic decoration of the best period, are much to be preferred; in the last two styles punches used with a hammer will greatly assist in lowering the groundwork, so that the design stands out in relief without the necessity of stuffing it, as in embossed work. By introducing gouache or bronzes into the impressions made with the punches, rich effects of colour can be produced.