The chrome tannage of butts for strapping and harness backs, and for motor butts and picking bands may be similar to that for chrome sole, but drum tannages are more common and the two-bath process is often used. In the latter case the acid chroming bath is preferred, using 6 per cent. of dichromate and of acid, with up to 15 per cent. of salt, and reducing with 15 per cent. thiosulphate and acid as needed. This process assists in the production of the light colour which is preferred in the case of some of these leathers. Strap butts after tanning are very thoroughly washed with cold water in pits, and repeatedly struck out by machine between the washings. They are then oiled with heavy mineral oil, and stretched by powerful machines. They are dried and curried during the stretching. Degras, wool fat and vaseline are greases used, and the drying and stretching finished off at 120° F. They are then fluffed on the flesh, French-chalked and heavily rolled. Harness backs are neutralized, machine sammed, and lightly fat liquored with 4-1/2 per cent. soap. They are then struck and oiled with heavy mineral oil and dried for stuffing. Hand stuffing, drum stuffing, and "burning in" are all used (see Part I., Section IV.). Stearin, paraffin wax, ceresin wax, wool fat, sod oil and mineral oil are the greases employed. The butts are blacked after stuffing with lamp black and oil, glassed well and buck-tallowed on the grain. Motor butts are fat liquored lightly, using soap only. They have to be softened, therefore, during the drying by being mechanically worked. A boarding machine is repeatedly used during the drying. They are finished off with French chalk on flesh and grain. Picking band butts are neutralized by using warm water and then borax solution, and are then sammed by machine and very heavily fat liquored with cod oil and tallow and hard soap, to which degras may also be added. Up to 20 per cent. of greases (on the pelt weight) may be used. They are well drummed in this, struck out, French chalked, and dried out. They are softened finally by machine. Waterproof chrome upper leathers are manufactured usually from hides tanned by the two-bath process, which is said to give a mellower leather. The neutral type of chroming bath is common. The butts are neutralized, machine sammed and struck, and then fat liquored with 2 per cent. each of neatsfoot oil and soft soap. They are then sammed, shaved and blacked on the grain with logwood and iron, and dried further. They are stuffed then by brushing with an abundant amount of concentrated fat liquor. This gives the waterproofness. They are staked after drying further, and often grained three ways. A further waterproof finish is given consisting of a fat liquor containing beeswax. They are finally brushed and re-oiled with linseed oil, to which some mineral oil may be added. This leather is much the most durable type for a shooting boot, or where waterproof uppers are desirable. REFERENCES.