Chapter XII: Section II: ). Lactic acid may substitute boric, in which case about 2

per cent. on the pelt weight of 50 per cent. acid may be required. It is important to avoid a strong solution and local excess, hence lactic acid must be added gradually so that the liquor is never stronger than 0.2 per cent. Drumming and paddling is an advantage in deliming.

The tannage is light in most cases, partly because some of the finished goods are sold by area, but partly also because even if sold by weight, the weight is obtained quicker and more easily by stuffing, which course is also often preferable to obtain the desired mellow feel, waterproofness and durability. Hence it is seldom that strong liquors are employed. The tannage is also mellow, on account of the softness and pliability required; no acids are consequently employed, and no material which is liable to yield sour liquors. Gambier is easily the first favourite amongst the tanning materials, whilst oak bark comes second. It should be observed, however, that a hypothetical tannage of equal weights of cube gambier and oak bark is in reality a tannage by four-fifths gambier and one-fifth oak bark, on account of the relatively greater strength of the former. This observation is so apposite with respect to some tannages that it is nearly correct to say that the tannage is gambier and the oak bark an excuse for having leaches through which the gambier liquors may be run occasionally to clear and to sharpen slightly. No serious theoretical objection to such a method is possible if the liquors are weak and the system of working the liquors is scientific and the process carefully regulated. Upper-leather tannages, however, have scarcely merited scientific praise. It is often a case, not of poor methods, but of no method at all. The same lack of system, principle, and regularity observed with regard to the limeyard has been equally obvious in the tanyard, when perhaps the need was even greater. Even a mellow tannage has varying degrees of mellowness possible to it; there still remains the question of the soluble non-tans. However, method in the upper-leather tanyard has often been conspicuously absent. There has been many a factory where any one tan liquor was as good as any other in the yard. In the writer's experience are two such cases: in one the liquors were all 25° Bkr., in the other they were all 0° Bkr. In such cases, handling the goods from pit to pit is somewhat futile, and handling forward from set to set still more so. Hence it is possible to find dressing leather tanned by putting it slowly through one round of handlers, adding a few buckets of gambier where it apparently is necessary. It is, from one point of view, surprising to see what serviceable and excellent-looking upper leather can be manufactured by such happy-go-lucky processes. It is, however, also possible to see how this may occur. Gambier is a stable tan, and no souring and little decomposition take place in gambier liquors. It is also extremely mild and non-astringent, and is always used in weak liquors. The hides, moreover, are completely delimed, and there is little danger of bad or uneven colour. Tanning under these conditions is at its easiest; it is almost more difficult to spoil the goods than make them right. Under such conditions tanning deteriorated rather than improved in method. When neglecting it made little difference to the finished leather, it was neglected.

This state of affairs, however, was embarrassing whenever a tanner wished to try any other tanning material. The expense of gambier and oak bark made valonia and mimosa bark into obviously desirable alternatives and substitutes. Methods which would tan with gambier, however, would not work with Natal bark or valonia, and many a tanner has had to revise his method of tanning from end to end. The use of myrabs also raised the problem of souring, and it has become evident that "working the liquors down the yard" is as desirable a method for dressing leather as after all other tannages. It will be clear from the above that types of upper-leather tannages are less typical than for other leathers, but nevertheless the more progressive manufacturers have for some years now been working on sounder lines, economically and scientifically. In such cases it is now usual to pass the goods through at least two sets of handlers, and through liquors of gradually increasing strength. Occasionally dusters or layers are given, especially for the heavier goods. The tannage is nearly always commenced now by paddling the goods in the oldest liquor. This paddling may be anything from half an hour up to twenty-four hours. It is sometimes desired to work up a "grain," and the old liquor is then often sharpened by the addition of fresh gambier or leach liquor.

The same tendency to save labour in handling is to be observed in upper leather tannages as in sole and other dressing leather factories. There is also a tendency to obtain rather more weight in tanning by using stronger liquors, and in the heavier goods to shorten somewhat the time taken. The following methods may be taken to illustrate modern processes, in order of evolution. They all last about seven weeks.

_Type 1_.--In this process the kips are first paddled in an old liquor (3°), and passed to the first handlers (3°-30°) for three weeks. After working through this set they pass through the second handlers (20°-30°), in which they are not handled quite so frequently. They are in this set also three weeks. Heavy goods may then receive a floater (30°) for another week.

_Type 2_.--In this process the goods are paddled, and then enter a large handler round (8°-30°), through which they pass in five weeks. The goods are handled frequently in the early stages. The tannage is completed by one layer of two weeks (30°). The layer is made by the ancient method of putting the goods and dust alternately into an empty pit, and then filling up with liquor from the best leach. Oak bark, valonia and myrabs are used as dust, though sumach and gambler have been used.

_Type 3_.--In this process an attempt is made to save handling and obtain more complete tannage. The goods are paddled for three to five hours in a rather sharp liquor of 10°, and are then handled well for a week in the first handlers (5°-20°). The goods then go through the second handlers (20°-45°) in six weeks, and heavy goods may then receive an extra floater (45°) for one week.

In type 1 the leaching material is two-thirds oak bark and one-third valonia; in type 2 it is half oak bark and half mimosa bark; in type 3 it is one-third oak bark, one-third valonia or Natal bark, and one-third myrabolans. In all cases the strongest handler is obtained from the leaches, and made up to the required with strong infusion of gambier. When the liquor has passed through the forward handlers, it is returned to the leaches to clear and sharpen, and then run to the green handlers. After passing through this round it is returned to the paddle, from which it passes to the drain. The rest of the paddle liquor may be from the forward handlers. It is often customary to obtain the best liquor from the second leach, and allow the best leach to stand for a few days. This allows the bloom to deposit in the leaches. The system secures the result desired, but the deposition of bloom involves a loss of tannin, which waste makes the system expensive.

Heavier dressing hides are tanned by methods similar to the above, but with floaters, dusters and occasionally layers added after they have passed through two sets of handlers. Thus they may have first handlers (8°-18°) two weeks; second handlers (40°-45°) for six weeks, making twelve weeks in all. Lighter goods may receive two rounds, being two weeks in each.

After tanning, the kips are rounded usually into butts, shoulders and bellies, to which different finishes are given. The currying may be illustrated by selecting types, but it must be borne in mind that there is much elasticity in this matter. Thus kips may be made into waxed butts, satin shoulders and lining bellies, but also may be cut down the back in "sides," both of which are finished limings.

Waxed kip butts are a type of many similar upper leathers (waxed shoe butts, waxed calf, waxed splits, etc.). The finish is on the flesh side. The kip butts are soaked carefully, and shaved by machine. They are then drummed in sumach for an hour or two, slicked out and sammed for stuffing. The sumaching is also the scouring unless the goods be too heavily bloomed. The samming is often done by machine. Drum stuffing follows, wool fat and stearin being staple greases, with varying amounts of degras and cod oil, and of tallow and cod oil. A little paraffin wax and resin are also used sometimes. The goods are well slicked out and dried. They may be now dubbined and laid away to mellow for whitening, which consists of a careful shaving of the flesh by a turned-edge slicker or by machine. The grain is stoned, set out and "starched," and the butts grained by boarding the flesh. In the waxing, one of two courses may be adopted. The butts may be blacked with lampblack and oil, "bottom sized" with glue, soap and logwood, and then "top sized" with glue, dubbin, beeswax and turpentine; or they may be given a "soap-blacking" of soap and logwood and lampblack, applied by machine, and sized once only.

Dressing hide butts may also be given a grain finish, such as the "memel butts" for heavy uppers. The butts are soaked, shaved or split, sumached in drum, and preferably thoroughly scoured on flesh and grain. They are then sammed and heavily stuffed in the drum. The grain is buffed and stained black with logwood, ammonia and iron solution (curriers' ink). The butts are then dried, set out, thinly sized and slowly dried.

When dry on the face they are printed or embossed by machine to give the characteristic memel pattern and dried out completely. They are then grained four ways. The grain is finished by a coating of linseed oil containing resin, and the flesh is whitened, French chalked and glassed.

Shoulders for "satin" receive a currying which strongly resembles the "waxed" finishes, but the smooth finish is on the grain side. The grain is buffed, and blacked, dubbined, set and reset, with intermediate drying, and is sized and finished by compositions similar to those used for waxed leathers. The flesh is whitened. Satin hide and satin calf are dressed similarly.

Shoulders may also be finished for "levant." After soaking, splitting, and shaving to substance, they are drum-sumached, machine-sammed, and oiled up to dry. They are stained with logwood on the grain, and at once printed with the typical "levant grain," blacked and dried out. They are then softened by machine, seasoned with logwood and albumen, glazed, grained and oiled lightly with mineral oil. It will be observed that stuffing is omitted.

Bellies may be dressed for linings. After soaking and splitting to the required substance, they are bleached in a weak and warm solution of oxalic acid, and drum-sumached at 110° F. After slicking well out they are hand-stuffed on the grain with dubbin and water, or merely oiled, and hung up to samm. They are then set-out flesh and grain. If the grain be coarse, it is buffed and reset. After drying out the flesh is fluffed and the grain dusted with French chalk.

In this section may be conveniently discussed the manufacture of legging leather. Whilst in many respects a typical dressing leather there are some rather important differences from the average upper leather. Broadly speaking, the differences are that legging leather needs a smooth grain, greater firmness and more thorough tannage on account of the absence of stuffing.

The liming and bating are somewhat similar to dressing leather, though a shorter liming with sulphides and a milder bating would be in order. The tannage is mellow, but not so much as is usual for upper leather. Thus gambier is used, but more valonia and myrabs are employed, and the liquors may be strengthened with chestnut and quebracho extracts. The hides are rounded before tanning into long butts or backs, and the tannage is commenced in suspenders (18°-40°), which are kept acid by the addition of lactic or acetic acid, in order to obtain the required firmness; the goods are three weeks in these liquors. The backs next go through rounds of dusters (40°-50°), in which they are put down with oak bark and Natal bark. They are six weeks in this section, and then pass to the layers. Three layers are given, first 50° for one week; second 55° for two weeks; and third 60° for two weeks. The tannage thus takes fourteen weeks.

In finishing, the goods are soaked and split, and then scoured flesh and grain. They are heavily sumached, slicked out thoroughly, oiled up with linseed oil and dried out. They are then next damped back, stoned and flatted. After further wetting and tempering they are dressed with Irish moss and tallow on the flesh, and with gum tragacanth on the grain. They are glassed whilst drying out, and then stained twice and glassed again. They are again brushed, seasoned and glassed by machine.

REFERENCE.

Bennett, "Manufacture of Leather," pp. 197-201 and 301-308.