12. Processes in leather manufacture

New words and word-combinations to be remembered:

adipose tissue жирова тканина

fleshing мездрування

tannage, tanning дублення

putrefaction гниття

currying жирування

dyeing фарбування

splitting шпальтування

dressing апретування

soaking відмокання

de-liming обеззолювання

tannery шкіряний завод

green-salted skins мокро-засолені шкури

skin шкіра

luclr велика шкіра

pelt шкіра, сировина

bating м'якшиння

puering м'якшиння

drenching киселювання (м'якшиння в киселі)

luffing жирування

tinning шліфування, полірування, пушення

masoning глянцювання, лакування, апретування

The first stage in leather manufacture comprises those operations which remove the epidermis and hair (or wool) and which render the idipose tissue so swollen that it is easily removed by fleshing. The aecond stage is the tannage of the corium by permeating it with a і iimmg agent or material to render it proof against putrefaction. The final or third stage consists of finishing, currying, dyeing or dressing, Mi

The processes that precede the actual tanning or conversion of hides and skins into leather are: washing, cleaning, fleshing, splitting, leaking, unhairing, do-liming, bating, puering, drenching, pickling.

As hides and skins are brought to the tannery in cured condition (green-salted, dry-salted and dried), the object of all these processes is і" bring the hides and skins to the natural soft condition it is in when removed from animal and in addition to remove blood, dirt, salt.

At the tannery skins and hides are properly washed and cleaned in large washing machines. To remove the excess flesh and fat from the ikins tanners use fleshing machine. Next operation is soaking. The object of the soaking process is to soften the hides and skins and to remove the salt dung, blood and dirt adhering to them.

I In- skins and hides are soaked in a lime solution to loosen the hair т.і epidermis so that it can be easily removed by the machine. Lime u.iil lot unhairing must be as free as possible from impurities. The period of liming has a marked influence on the finished product.

Limed hides and skins contain some lime which would interfere with the tanning process so it is advisable to remove it from the surface layers of the pelt.

Ordinary de-liming may be accomplished by weak organic acids or certain chemicals, while bating, puering and drenching, all of which tend to produce soft leather, must be brought about through fermenta­tive, bacterial or enzyme action.

After drenching of sheep, goat pelts and of bated calf and light hide pelts, they are usually pickled with salt and sulphuric acid. Sheep-skin pelts are pickled to preserve them.

The series of processes by which the natural skins are converted into leather is covered by the term "tarining". The рифове of tanning is to convert raw hides and skins into leather, to render the hide imputresci-bility, that is resistant to putrefection.

Hides and skins tanned absorb certain properties of the agents with which they are tanned.

There are several methods of tanning, each producing special type of leather with special characteristics: vegetable, chrome, oil, alum, formaldehyde, synthetic, zirconium and combination tanning.

The finishing processes that follow tanning are numerous and of great importance in converting a harsh, stiff material into the beautiful finished leather.

They are: setting-out, drying, stuffing, currying, staking, fat-liquor­ing, buffing, seasoning, rolling, glazing, polishing, ironing, embossing, dressing, dyeing, etc.

These final operations are numerous and depend in large part upon the type of finished leather required.

Answer the following questions:

1. What are the main stages in leather manufacture?

2. What are the processes that precede the actual tanning?

3. What is the object of soaking, fleshing, liming, unhairing?

4. What is the chief purpose of tanning?

5. What finishing processes do you know?

Speak on the processes in leather manufacture using the following word-combinations:

— three stages in leather manufacture;

— the processes that precede the actual tanning: washing, cleaning, fleshing, soaking, unhairing, etc.;

— the purpose of tanning, the methods of tanning;

— the finishing processes that follow tanning;

— to depend upon the type of finished leather required.