CHAPTER VII._The Puering, Bating & Drenching of Skins

ARTIFICIAL BATES.

As may be supposed, inventors have from very early times turned their

attention to the substitution of some other material in place of the

unappetizing one so long in use. But as I pointed out in a short

article entitled “Rationale of Bating”[133] many of them looked upon

bating and puering as a process for removing lime from the skins,

and nothing more; whereas we have seen that it is a very complicated

process in which, not only is lime removed more or less effectively,

but the skin fibres are acted upon, and portions of them rendered

soluble, and the skin thus got into the necessary condition.

[133] Leather Industries, Sept. 1898.

This misconception of the object of bating or puering prevented the

success of most inventions of artificial bates up to quite recent

times. Procter states that the use of ammonium chloride as a bate was

patented by Zollikoffer in 1838. Such agents as this, and various

acids, which have been proposed are merely chemical deliming agents,

and, as such, we do not propose to discuss their use as artificial

bates. Procter[134] gives an excellent account of these processes,

including one of his own, in which ammonium chloride is used in

conjunction with metabisulphite of soda, and for successive packs

sufficient sulphuric acid is added to neutralize the ammonia formed.

[134] Principles of Leather Manufacture, p. 160.

The same author[135] also mentions an American invention for bating

by the use of old lime liquors neutralized with sulphuric acid. This

method is much more scientific than would at first sight appear, and

more nearly approximates to the conditions of the dung bate than any of

the early inventions. Old lime liquors contain much ammonia and weak

organic acids, such as caproic, amido-caproic (leucin) and tyrosin.

On adding sulphuric acid, the lime forms an inert sulphate, and the

sulphate of ammonia and the weak organic acids which remain dissolved

are just what are required in a chemical bate. The author has used this

bate with success on certain classes of goods.

[135] Text Book of Tanning, 1885, p. 185.

*Tiffany’s bate*, which is used in America, is composed of glucose and

glue, and bates of this composition are also in use in England. As an

example, 10 lb. glucose and 1/2 lb. of glue dissolved in 1000 gallons

water, at a temperature of 75° F., and allowed to ferment for a few

hours, may be used for the bating of bellies, and if used in a paddle

or latticed drum will bring them “down” very rapidly.

Davis[136] gives a list of twenty-nine patents for bating issued by the

U.S.A. Government from 1790 to 1883 inclusive. I do not know whether

any of these are in use at the present day.

[136] The Manufacture of Leather, Philadelphia, 1885.

*Erodin.*--Since the publication of the authors researches on the

constitution and mode of action of the dung bate, renewed attention has

been given to the construction of bates, or puers, having an identical

action. One of these has been worked out by Professor Dr. H. Becker, of

Frankfort o/M, in conjunction with the author under the name of Erodin

(Latin, _erodere_, the equivalent of the German _beizen_--to bate).

As this was the first artificial bate in which a pure culture of

bacteria has been applied to the treatment of skins, I propose to

describe it in some detail.

Erodin[137] consists essentially of a nutrient material in the form of

powder and of a pure culture of _B. erodiens_ which is added to the

powder mixed in a definite quantity of warm water (40° C.). On the

average about 10 grm. of this material is sufficient to bate one kilo

of wet prepared skin.

[137] At the third Conference of the I.A.L.T.C., held in Copenhagen

Aug., 1899, F. Kathreiner (Worms) brought forward communications from

Wood (Nottingham) and Dr. Becker (Frankfort-on-Main) on artificial

bates, from which it is shown by experiments and trials on a large

scale at the works of Messrs. Doerr and Reinhart that both these

gentlemen had worked out similar processes quite independently. Wiss.

Techn. Beilage des Ledermarkt, 1899–1900, p. 8. Bemerkungen über die

Wirkung der Kothbeizen, J. T. Wood. Idem, p. 43.

Popp and Becker’s und Wood’s Ersatzmittel für Köthbeizen. Franz

Kathreiner. Idem, p. 50.

Einiges über die Anwendung von Erodin einem Ersatzmittel für

Hundekoth u. dergl. in der Leder industrie. Bericht von Dr. H.

Becker, Frankfort-on-Main. Wiss. Techn. Beilage des Ledermarkt. Bd.

i., p. 39.

Further particulars about the bate and its construction will be found

in Chapter VIII.

In practice it is found that this material acts far more energetically

on the skins when living bacteria are present in the liquid; we

suppose that they penetrate the skin and form their products in the

intercellular spaces. It was found that, in the evaporation of the

cultures to dryness, the bacteria were mostly killed or so far reduced

in activity, that on preparing the bate after a certain lapse of time

it was liable to become infected by foreign organisms.

In order to ensure uniform results a pure culture of the special bating

bacteria is supplied with every 5 kilos of the erodin powder. The

weighed amount of erodin is placed in a perfectly clean mashing-tub,

with 50 times the weight of water at a temperature of 40° C. a pure

culture of Bacillus erodiens is added to the mixture, and the whole

covered with a clean cover and allowed to stand for two or three days.

A little steam is admitted morning and evening so as to maintain the

temperature at about 40° C., or some other suitable device for heating

is applied. Several tubs may be kept in a small stove heated to the

right temperature by steam pipes. In this way the bating bacteria

develop rapidly, and if the proper precautions as to cleanliness and

temperature have been observed, there is no fear of any adventitious

germs getting the upper hand. As soon as a vigorous growth is attained,

usually on the third day, the bate is ready for use.

Erodin is in use on a fairly large scale, and, as is usually the case,

difficulties have arisen on a manufacturing scale which do not occur

in the laboratory. In the practical application of the material the

mashing-tub may be 3 ft. 9 in. in diameter and 3 ft. 3 in. in height

and of a capacity of 200 galls. Steam is admitted directly by means of

a copper pipe fitted with a boiling jet.

The goods are bated in the ordinary bating paddle or puer wheel

(Fig. 3, p. 13).

During the year 1901 about 9000 dozens of sheep “grains” were puered

with Erodin at Trent Bridge Works (Messrs. Turney Brothers, Ltd.)

Nottingham, and considerable experience gained in its use.

The mode of operation was as follows:--On Fridays 30 kilos of Erodin

powder was mashed in a wooden vessel in 1600 litres water at 40° C. and

inoculated with a sufficient quantity of a pure culture of B. erodiens.

The temperature was kept at 35°–40° C. by admission of a little steam

first thing in the morning, again at noon, and in the evening, and the

liquid so prepared was ready for use on Monday. One wheel or paddle was

kept going for the work. To start the operation, 200 litres of stock

liquor was put into the wheel, and sufficient water added for the goods

to turn freely. The skins previously washed, as described in Chapter

I., were paddled until sufficiently “fallen” or “down.”

For the following lots, the liquor was strengthened by the addition

of 100 to 140 litres of the stock liquor, the wheel being run off and

cleaned out once a week. The general result showed that “high-limed”

skins and previously salted skins were more refractory to this bate

than to dung.

As in the English system of collecting pelts there are all stages of

liming, skins containing from 1.5 to 9 per cent. CaO on the dry skin,

it is not surprising that considerable difficulty was experienced in

keeping the puering uniform. Skins containing over 3 per cent. CaO

on the dry skin, seem to require a real putrefactive action in order

to “bring them down” sufficiently, or it may be that their alkalinity

is too great to allow the bating enzymes to act properly. It may here

be said that if the fibres of skin are actually damaged by excessive

action of lime or any other chemical, no subsequent treatment is of

avail to remedy the defects.

Shearling pelts were excellent when puered with erodin, a further proof

that the alkalinity is of importance, since these pelts do not require

so much lime as “old fells” to bring them into proper condition for

splitting.

For sheep and calf skins treated from the market condition and

consequently containing a uniform amount of lime--2–3 per cent.--the

process is quite reliable, and is in practical use on a large scale.

Goat skins have been successfully bated with erodin by treating them

in a concentrated liquor in a drum,[138] instead of a paddle, the

mechanical effect of the drumming enabling the bate to penetrate the

hard and compact skin, while the more concentrated solution of the

enzymes attacks the so-called “beard,” and renders the skins as supple

as sheep skins bated in a paddle.

[138] One litre of erodin stock liquor (1 part erodin, 40 parts

water) were used per kilo drained washed pelt, in the drum for 1-1/2

hours. In some cases less than 1 litre sufficed.

It may be of interest to give here some of the results of the early

trials of erodin in a tabular form, due to the late Franz Kathreiner.

They are a further proof of the thoroughness with which he carried out

all his work.

LEATHER, N.F. AND KALOCHROM. Date of Trial, Nov. 22, 1898.

---+---------------------+--------+-----------+----------+------------

No.| Test | E 47 | B 3 | B 4 | B 5

---+---------------------+--------+-----------+----------+------------

| | 21/9/98| 1/11/98 | 1/11/98 | 1/11/98

| | | | |

| | | | |

3 | " total quantity| 500 gr.| 26 L. | 13 L. + |

| | | | 700 gr. | 13 L.

| | | | |

4 | " quant. per kilo| | | |

| | | | |

5 | " quant. per kilo| | | |

| | | | |

6 | " quant. per kilo| | | |

| | | | |

7 | | | | |

| | | | |

8 | | | | |

| | | | |

9 | | | | |

| | | | |

10 |Water used | 260 l. | 210 l. | 140 l. | 125 l.

| | | | |

11 |Temperature of bate | | | |

| at 10.25 | 34° R. | 34° R. | 33° R. | 32° R.

| | | | |

12 | " of bate | | | |

| at 10.30 | 28° | 27° | 28° | 26°

| | | | |

13 | " of bate | | | |

| at 2.30 | 26° | 25° | 25° | 24-1/2°

| | | | |

14 |Time run | 4 hrs. |3-1/4 hrs. |3-1/4 hrs.|3-1/4 hrs.

| | | | |

15 | " standing | -- | 1/2 hr. | 1/2 hr. | 1/2 hr.

| | | | |

| | | | |

17 |Acidity of 50 c.c. |0·2 N/10| 1·8 N/10 |1·15 N/10 | 2·7 N/10

| | | | |

18 | " 50 c.c. | | | |

| after kaolin| -- | -- |1·15 N/10 | --

| | | | |

19 | " 50 c.c. | | | |

| | | | |

20 |Alkalinity of 50 c.c.|1·2 N/10| 2·2 N/10 | 1·4 N/10 | 1·3 N/10

| | | | |

21 | " 50 c.c.| | | |

| | | | |

22 | " 50 c.c.| | | |

| | | | |

23 |No. of skins and size| 45 X | 46 X 3 | 23 X | 23 X

| | | | |

24 |Weight after | | | |

| | | | |

25 | " " | | | |

| | | | |

| | | | |

27 | " " " | | | |

| | | | |

28 | " " striking | | | |

| out | 77 | 77 | 36 | 36

| | | | |

29 |Invoice | | | |

| | | | |

30 |Date of soaks | -- | 5/11/98 | -- | --

| | | | |

31 |Mark | -- | T. 71 | -- | --

| | | | |

32 | | | | |

| | | | |

33 | | | | |

| | | | |

34 | | | | |

---+---------------------+--------+-----------+----------+-----------

_Remarks._--22 skins of E 47 after 3 hours running had 250 c.c. 70 per

cent. lactic acid; they were marked with a hole in the tail; were more

fallen than the others.

_Judgment after Scudding._--All lots well down; E 47 whitest colour;

all smooth grain, E 47 and B 3 smoothest. The 3 goat were not low

enough.

It was observed both in laboratory experiments[139] and in practical

work that the presence of solid matter in the puering liquor had a

considerable influence on the speed at which the goods fell. The

clearer the liquor the slower the action. The explanation of this

fact is not quite clear. Possibly the finely divided solid matter

acts as a carrier for the enzymes, each particle offering a very

extended surface, or it may be that the action of the solid matter is

mechanical, like that observed in bran drenching.

[139] J.S.C.I., 1899, p. 910. See also p. 73.

The goods puered with erodin, whether split or unsplit skins, should be

scudded on the grain. Sheep splits are scudded with a machine of Sir

John Turney’s type. (Fig. 6, p. 17.) Roans and goat may be scudded with

any of the spiral knife machines (Turner, Mœnus, etc.) in general use.

The following figures, p. 187, giving the reactions of an erodin bate

in c.c. N/5 alkali or acid required to neutralize 50 c.c. filtered

bate, are of interest as being taken from actual work. They were kindly

communicated to me by Herr Karl Schorlemmer, chemist to Messrs. Doerr

and Reinhart, of Worms.

Erodin, tested by the electrometric method, was found to have the

following hydrogen ion concentrations:--Paddle before goods, π = 0·672

volt, equivalent to a hydrogen ion concentration p_{H+} 6·6. The same

liquor after goods, π = 0·710, equivalent to p_{H+} 7·3. Compare puer

liquors, p. 79.

---------------+--------------+-------------

Bate | Before Goods | After Goods

---------------+--------------+-------------

1. Old | 0·05 alkali | 0·4 acid

2. Fresh | 0·15 " | neutral

3. Old | 0·05 " | 0·55 acid

4. Fresh | 0·2 " | 0·05 "

5. Old | 0·1 " | 0·1 "

6. Fresh | 0·45 " | 0·15 alk.

7. Old | 0·15 " | 0·3 acid

8. Fresh | 0·5 " | 0·1 alk.

9. Old | 0·1 " | 0·3 acid

10. Fresh | 0·3 " | neutral

11. Old | 0·1 " | 0·7 acid

12. Fresh | 0·2 " | 0·05 alk.

13. Old. | 0·1 " | 0·25 acid

14. Fresh | 0·4 " | 0·15 alk.

15. Old. | 0·05 " | 0·3 acid

16. Fresh | 0·45 " | 0·1 alk.

Mean of old | 0·087 " | 0·31 acid

Mean of fresh| 0·33 " | 0·051 alk.

---------------+--------------+-------------

*Oropon.*--An interesting application of the theory of the bating

process which was put forward by me[140] is that of Dr. Otto Röhm[141]

in 1908, in which, instead of a bacterial culture, he employs an

infusion of pancreas in conjunction with ammonium salts. This bate has

been put upon the market in the form of a powder under the name of

Oropon.

[140] J.S.C.I., 1898, p. 1013.

[141] See Chapter VIII.

The approximate composition is:--

Per cent.

Ammonium chloride 65

Wood fibre 31

Dry pancreas about 3·5

The nitrogen unaccounted for by ammonium chloride is 0·32 per cent.

Its chief advantage is the simplicity of application, no previous

fermentation being required. About 5 oz. to 9 oz. are required per

100 lb. wet pelt, and it is recommended to soften the water by adding

a certain quantity of clear lime water to it previous to making up the

puer.

Its disadvantages are, that unless a previous bath is used, the

quantity of ammonia given off is detrimental to a proper bating action,

so that for good working a preliminary bating is required. Another

disadvantage is that the whole of the enzymes being in the bate their

action is more superficial and the grain may be puered too much while

the interior of the skin is not penetrated by the enzymes.

The author has made some experiments with an enzyme bate using ammonium

butyrate instead of ammonium chloride, and castor oil seed meal in

place of the wood fibre.

It was found that the amount of ammonium salts in solution in the most

effective bate was approximately one gram per litre. The bating liquid

was therefore made up as follows:--

Ammonium butyrate 1 grm.

Castor oil seed meal 2 "

Dry pancreas 0·01

Water 1000 c.c.

This liquid at 40° C. bated a skin well in one hour. On increasing

the quantity of castor oil seed meal to 4 grm. per litre, the bating

effect was not so good. Substituting 0·5 c.c. liquor pancreaticus

(Benger) for the solid pancreas, the bating effect was too powerful,

the thinner skins were attacked by the bate, and the grain destroyed

in patches in a very similar manner to over-puered skins. Further

experiments showed that a little more than one-tenth of this amount of

pancreatic solution per litre would be sufficient (70/100 c.c. liquor

pancreaticus per 1000 litres).

Castor oil seed contains a lipatic enzyme, and when shaken up with

olive oil will emulsify the oil. 75 grm. castor oil seed meal, and

10 c.c. of olive oil were shaken up with 490 c.c. of water and formed

a perfect emulsion, no fat being visible on the surface of the liquid.

The mixture was diluted to 7 litres, and a grain treated in it at

40° C. for half an hour; it was fairly well bated in this time, and

had a smooth slippery feel, such as skins have in the puer, but was

perceptibly “higher” than the skins bated in the new bate containing

pancreatin.

This experiment appears to confirm the fact that a mixture of enzymes

is necessary, or, at any rate, that a lipatic enzyme alone is

insufficient for complete puering.

*Dermiforma.*[142]--This is an American preparation, put on the

market by the Nowak Manufacturing Co. of Chicago, and is described as

a natural bacterial liquor of organic acidity. For 1200 lb. scudded

calf skins, 9 gallons of the liquid Dermiforma are used at 100° F.,

one-third being put in to start with and the remainder added gradually;

time required, about 3 hours. For sheep skin a less quantity is

required. This bate was found to be a preparation of whey, and contains

a certain quantity (18–20 per cent.) of lactic and other organic acids,

produced by fermentation; it is therefore to be classed as a drench,

and is not a true bate or puer, since tryptic ferments or bacteria are

not present.

[142] See Chapter VIII.; also J.S.C.I. 1906, p. 647.

*Puerine.*--Another bate, manufactured in America is advertised

under the name of Puerine, “the long-looked-for bacterial bate.” The

manufacturers give the following directions for use. To start a bating

liquor, 10 lb. of the dry powdered puerine is put into a half barrel of

warm water (100° F.), and allowed to stand for 3 or 4 days, maintaining

the temperature by occasionally warming the infusion with a steam pipe.

This amount is sufficient for each 100 galls. water in the bating vat

or paddle wheel, and will bate as many skins as can be turned in 100

galls. When the warm infusion of puerine has stood the required length

of time, in order to generate the necessary bacterial ferments, the

bating vat is run up with warm water say, 100 degrees in warm weather

and 110 in cold weather, and the infusion of puerine, including the

undissolved portion, is added to the bating vat, and the skins entered

into the bating liquor. As the action of the puerine on the skins is

exactly the same as a dung bate, the judgment of the operator must

determine when the skins are “low enough.” It is not necessary to

make a fresh bating liquor for each pack of skins, because the bating

liquor improves with age. With each succeeding pack of skins, enough

warm water is added to the bating vat to make up for the loss of liquor

which is occasioned by the removal of the previous pack, and from 3

to 5 lb. of puerine for each 100 galls. added directly to the bating

liquor; it is then in condition immediately to use again.

The bate was found to consist of

Sugar.

Gelatin.

Sodium }

Ammonium } Chlorides and sulphates.

Bisulphite of lime.

Meal.

As it is allowed to ferment without the addition of bacteria, it will

be seen that it acts in quite a different manner to erodin, being more

of a modified drench than a true bate, and is not in any way a perfect

substitute for the dung bate.

*Sucanine.*--This is a French bate, put on the market by Messrs. Muller

and Co., Rouen; it is described as “concentrated dog puer, chemically

clean, i.e., all foreign matters have been eliminated and it contains

only that which is really necessary.” The directions state that the

quantity to be used is the same as of dog puer prepared ready for use.

The paddle is kept at a temperature of 30° C.

This material was found to be a liquid containing ammonium sulphide,

phosphates and chlorides of sodium in solution, a considerable quantity

of solid matter in suspension consisted of calcium phosphate and

calcium sulphide. There was sufficient organic matter to permit of

bacteria growing in the diluted liquid.

It had no harmful effect on skins and “brought down” most sheep skins

in an effective manner; some resistant skins appeared to require

further puering.

*Purgatol* is a patent bate put on the market by Dr. G. Eberle and

Co., of Stuttgart. 1-3/4 lb. is said to be sufficient to bate 100 lb.

wet pelt in 1–2 hours at 38°–40° C. It is a dark brown liquid with an

unpleasant smell. When boiled with potash it gives volatile alkaline

products.

Distilled with sulphuric acid it gives an acid distillate consisting

of organic acids mostly of the fatty series. It contains amines and

volatile nitrogenous bases, but no enzymes or bacteria. It must

therefore be classed as a deliming agent and not as a true bate or puer.

*“Esco.”*--This recent artificial bate is of an acid character, and

is said to have an action intermediate between the bran drench and

pigeon dung; it contains no animal enzymes, but appears to contain some

vegetable enzymes of a lipatic character; it also contains 18 per cent.

of ammonium chloride in which respect it resembles “Oropon.” It is

manufactured by E. Stickelberger and Co., Haltigen, near Basle.

Other artificial bates are treated of in the next chapter under the

respective patents. There is also an interesting article on new bates

by Eitner in Der Gerber, Nos. 878 and 879, 1911. See also Collegium,

1911, p. 402.