CURRYING.

In general terms, the process of currying consists in softening, levelling, and stretching the hides and skins which are required for the upper-leathers of boots, and other purposes demanding flexibility and softness, and in saturating or "stuffing" them with fatty matters, not only in order to soften them, but to make them watertight, and to give them an attractive appearance.

It is obvious that great differences must be made in the currying process, according to the character of the skin and the purpose for which it is intended, since the preparation of French calf for a light boot, and of the heaviest leather for machine belting, equally lie within the domain of currying. In this case, however, as in that of tanning, the clearest idea of the general principles involved will be gained by taking a typical case, and afterwards pointing out the different modifications needed for other varieties. The French method of currying waxed calf is selected as an example, since the well-known excellence of this leather makes it interesting to compare the details with the methods ordinarily in use in this country.

After raising the skins from the pits, and beating off the loose tan, they are hung in the sheds till partially dry (essorage), great care being taken that the drying is uniform over the whole skin. In modern shops, this drying is usually accomplished at once, and in a very satisfactory manner, by means of a hydraulic press. If dried in the air, they must be laid in pile for a short time to equalise the moisture, and then brushed over on flesh and grain. The next process consists in paring off loose flesh and inequalities (dÉrayage). This is done on a beam, and with a knife similar to that used in bate-shaving, and shown in A, Fig. 26. This knife has the edge turned by rubbing with a strong steel, and is called couteau À revers.

Next follows the mise au vent. The skins are first placed in a tub with water or weak tan-liquor for 24 hours; they are then folded and placed in a tub with enough water to cover them, and beaten with wooden pestles for ¹/₄ hour. At the present day, stocks (foulon vertical), or a "drum-tumbler" (tonneau À fouler), a machine on the principle of the barrel-churn, usually take the place of this hand-labour. The skin is next placed on a marble table, flesh upwards, and with one flank hanging somewhat over the edge, and is worked with a "sleeker" or stretching-iron (Étire), B, Fig. 26. The first 2 strokes are given down and up the back, to make the skin adhere to the table, and it is then worked out regularly all round the side on the table, so as to stretch and level it. The flesh is then washed over with a grass-brush (brosse À chien-dent), the skin is turned, and the other flank is treated in the same way. It is lastly folded in 4, and steeped again in water. The next process is the cleansing of the grain. The skin is spread again on the table, as before, but grain upwards, and is worked over with a stone (coeurse), set in handles, and ground to a very obtuse edge. This scours out the bloom; after washing the grain with the grass-brush, it is followed by the sleeking-iron, as on the flesh.

The next step is resetting (retenage). For this, except in summer, the skins must be dried again, either by press or in the shed. This is another setting out with the sleeker, and, the skin being dried, it now retains the smoothness and extension which is thus given to it. The skins are now ready for oiling in the grain, for which whale-oil or cod-liver oil is generally employed. Olive-oil, castor-oil, and even linseed-oil may, however, be used, and are sometimes made into an emulsion with neutral soap and water. After oiling the grain, the skins are folded and allowed to lie for 2-3 days before oiling the flesh.

The oiling on the flesh is done with a mixture of dÉgras and tallow, in such proportions as not to run off during the drying. DÉgras is the surplus oil from the chamois-leather manufacture, which in France is effected by daily stocking the skins with oil, and hanging in the air for oxidation. The dÉgras (toise, moËllon) is obtained, not by washing the skins in an alkaline lye, as in the English and German method, but by simple pressing or wringing. This oil, altered by oxidation, is so valuable for currying purposes that skins are frequently worked simply for its production, being oiled and squeezed again and again till not a rag is left. It is generally mixed in commerce with more or less of ordinary fish-oil. Eitner recommends, where the dÉgras is of indifferent quality, a mixture of 65 parts dÉgras, 20 of neutral soap (i. e. soap without the usual excess of alkali), and 15 of soft tallow. After oiling the flesh, which is accomplished by extending the skin on the marble table with the sleeker, and applying grease with a sheep-skin pad, it is hung to dry at a temperature of 65°-70° F. (18°-21° C.). After drying, the surplus oil is removed by a fine sleeker from both flesh and grain, and the skins are ready for "whitening" (blanchissage). This consists in taking a thin shaving off the flesh, and was originally accomplished by the shaving-knife on the currier's beam, and some curriers are still in favour of this method. It is now, however, usually done by a sleeker with a turned edge. The grain then undergoes a final stoning and sleeking, to remove the last traces of adhering oil, and the skin is grained by rubbing it in a peculiar way under a pommel covered with cork. It is then coated on the flesh with a mixture, of which the following is a specimen:—5 parts of lamp-black are rubbed with 4 of linseed-oil, and 35 parts of fish-oil are added; 15 parts of tallow and 3 of wax are melted together and added to the mixture; and, after cooling, 3 parts of treacle. This compound is put on with a brush, and allowed to dry for some days. Finally, the skins are sized over with a glue-size, which is sometimes darkened by the addition of aniline-black.

The preceding account will give some idea of the care and labour expended on these goods in France. In England, cheaper productions are more in vogue, and almost every process is accomplished by machinery. An illustration of the Fitzhenry or Jackson scouring-machine, which is largely employed both for scouring and setting out, is given in Fig. 53. This is a simple and efficient machine, and has been largely used, both here and in America.

Fig. 54 shows the improved tool-carriage introduced by C. Holmes of Boston, in which the brush and sleekers or stones are controlled by handles which are stationary instead of moving rapidly with the slide, as in the older form. Spiral springs are also substituted for the older elliptical ones.

The Fitzhenry machine has also been constructed so as to work in any direction over a fixed table, being driven by a small direct-acting steam-cylinder supplied by jointed pipes. But probably the most perfect scouring and setting machine which has yet been introduced is the Lockwood Automatic Scourer, which may also be regarded as a development of the Fitzhenry machine. This has been some years in use in America with great success, and has received considerable improvements, but has only very recently been introduced into England by Messrs. Schrader and Mitchell of Glasgow, who have kindly furnished the annexed illustration (Fig. 56). In this machine the table is fixed, and the tool-carriage can be moved over it in every direction. The large projecting carriage, or cross-head, which supports it, travels on a horizontal rail, which may be observed below and behind the table. Motion is given to it by a screw which is driven in either direction by the pulleys at each side of the cross-head. In a similar way the tool-carriage is traversed forwards or backwards by a second screw at right angles to the first, and by a most ingenious interlocking arrangement both screws are controlled by a single handle. The tool-carriage or "trundle frame" can also be turned like a turntable, so as to deliver its stroke in any direction, the tool-holder being « 199 »
« 200 » driven by a horizontal crank in the centre of the frame, and immediately above the tools. Though the machine is complicated, and necessarily expensive, it has not been found either in America or Scotland difficult to work or liable to get out of order, while both the quantity and quality of its work are all that can be desired. Fig. 55 is GlÄser's scouring machine. Fig. 57 illustrates the latest English scouring machine, Messrs. Haley and Co.'s Climax Scourer, which is also ingenious and effective. In it the table instead of the tool-holder is movable by screws driven by belts thrown into gear by a handle, and it is provided with two tables of which one is in work while the hides are being changed and spread on the other. The oscillating tool-holder, instead of being actuated by the rise and fall of the connecting-rod, is moved by an adjustable eccentric.

In the case of strap-butts, the currying is, of course, far less elaborate. They are well scoured out, heavily stuffed, and stretched in screw-frames, to prevent their giving afterwards when in use.

In Germany, Switzerland, and Austria, a method of stuffing strap-butts is frequently employed, which, so far as I am aware, is not in use in England. It is called Einbrennen or "burning in," and consists in applying very hot tallow to the dry leather. The butts are washed free from liquor in a tumbler, boarded to soften them thoroughly, scoured, set out with a sleeker, nailed on laths, and air-dried. They are then very completely dried in a room heated to 104°-113° F. (40°-45° C.), as if any moisture remains in the hide, the fibre will be destroyed by the heat of the melted tallow. The tallowing generally takes place in the same room, as a high temperature is required to allow it to soak in, and the leather would greedily reabsorb moisture if exposed to damp air. The tallow is heated, generally by steam in a jacketed pan, to 167°-212° F. (75°-100° C.). There are two ways of applying it. The melted tallow may be applied on a table to the flesh side of the butt with a ladle, and rubbed on with a brush or rag. In this case, as soon as the tallow has sufficiently soaked in, the butts are placed in water to prevent its striking through to the grain. The second way is to have the pan of sufficient size and suitable shape, and for two men to draw the butt through the melted tallow with tongs, and more or less rapidly according to the quantity it is desired that the leather should absorb; and in some cases the process is repeated once or more. In this case, it is useless to wet in water, and the butts are allowed to cool gradually in pile.

The leather is now impregnated with grease, but it is far from being properly stuffed. Instead of the grease being spread over the finest fibres in a minute state of division, it simply fills the spaces between the larger fibres. To remedy this, the butts are well softened in water (which, if they have been drawn through the tallow and allowed to cool, must be tepid), and are then worked in a damp condition in a drum tumbler, by which they brighten in colour and become uniformly stuffed. They are then allowed to lie in a pile a day or two, are stoned and worked out with the sleeker, and hung up to dry. When in right temper they receive a final setting out with the sleeker, and when dry are either rolled or glassed. For further details, Nos. 256 and 257 of 'Der Gerber,' 1885, must be consulted, where the matter has been exhaustively treated by Eitner, in his papers on "Extract-Gerberei."

In England, curried leathers are generally sold by weight, which leads to the use of glucose and other materials to add to the weight. In America, all upper leathers are sold by measure, and this is now ascertained by a very ingenious machine (Fig. 58). The skin is laid on a latticed table, and a frame, from which rows of bullets are suspended, is let down upon it. The total weight of the frame is indicated by a spring balance, and as the bullets which are over the skin are supported by it, the diminution of weight indicates the measurement. Several modified forms of this machine are now made.