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Wattle-Barks in General.

(a). Time of year for stripping.

Wattle-barks are often gathered all the year round, whereas they should only be stripped for three or four months in the year; (the months recommended are September, October, November, and December)note out of that season there is usually a depreciation of tannin in the bark. In these months, also, the sap usually rises without intermission, and the bark is easily removed from the tree. The impression appears to have prevailed amongst bark-strippers that whenever the bark would strip it possessed full tanning properties, but this is erroneous. After a few days of rain during other seasons of the year, a temporary flow of sap will cause the bark to be easily detached from the trunk, but then it is greatly inferior in quality. (Report Victorian Board).

Mr. A. L. Thrupp, in a paper read in March, 1890, before the Congress of Agricultural Bureaux in Adelaide, carefully warns tanners and others against receiving wattle-bark damp, pointing out that bark in that state engenders mould “of a most virulent form,” is liable to spontaneous combustion if stacked in the hold of a vessel, and, while bark received green will tan hides as fast as bark received dry, still, there is the undeniable fact, in nine cases out of ten, that leather produced from bark so received, so stacked, and used for tanning purposes is spotted, and therefore of second rate or third rate value.

Apart from the intermittent supply already alluded to, it is owing to the greedy and indiscriminating way in which wattle-bark has been gathered, and the moist condition in which it has often been shipped, that purchasers in England, finding the quality variable, have not entered into its regular employment as largely as might have been expected.

It should be purchased in the stick or bundle. “In this form its quality can be more readily judged; but when the supply of mature trees became diminished, nearly all the bark was chopped or ground prior to shipment, good and inferior being bagged together.”

Mr. Thrupp states that if the bark of a wattle-tree of three or four years be slit down on the south side with a sharp knife, from root to first branch. the increase in the bulk of the bark will be considerable. This has been tried in the Montacute District of South Australia successfuly for years. Spring is the proper time for this work. (Journal, South Australian Bureau of Agriculture, November, 1889.) A correspondent of mine, engaged in wattle cultivation in the Blue Mountains, has also practised this method with success. He has instituted comparative experiments, and is convinced of the advantage of the process in increasing bulk of bark. He performs the operation in the early winter (May or June).

The best wattle-barks contain comparatively little fibre. A good bark will, as a rule, grind to an impalpable powder, while one which with the same treatment forms a fibrous substance is, as a rule, to be avoided. I have not, however, come to any conclusion with respect to the connection between percentage of tannic acid and fibre.

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(b). Age and Size of Trees.

Wattle-bark should only be procured from mature trees, i.e., from those whose bark possesses the full natural strength. The Victorian Board states, as has already been noted, that bark-stripping may profitably commence at the end of the fifth year, and returns undoubtedly commence not latter than this period. Mr. J. E. Brown strips his wattles at about 6 years of age, but the exact period can only be decided by the cultivator's common sense. Mr. A. Bucknall mentions that wattle trees mature in seven years in the Majorca plantation, Ballarat. Mr. W. Ferguson of Victoria makes the general statement that none should be cut under 5 inches in diameter,—a reasonable suggestion which might be enforced, on Crown lands, by legislative enactment.

Some people fell their wattles before stripping, and use the wood for firewood. Bark-strippers as a rule leave about a third of the bark on the tree, besides leaving unsightly dead trees. It should also be borne in mind that dead and decaying trees are a source of danger to the plantation, owing to the harbour they give to insect pests. The matter of utilizing the bark on the twigs, &c., will be alluded to below.

Mr. Thrupp states, as his experience, that greater weight of bark can be produced in five years when cultivated, as against 8 year old bark grown in its natural state (Journ. S. A. Bureau Agric., April, 1890). It is to be hoped that farmers and others will institute some experiments with the view to estimate the improvement in quantity and quality of wattle-bark under cultivation, but such experiments, to be conclusive, must have the data carefully checked, in order to make sure that the comparisons of wild and cultivated trees are as fair as possible.

(c). Export, Packing, &c.

In regard to the preparation of bark for export, the following letter from a well-known London firm of brokers, which appeared in the Leather Trades' Circular and Review of the 8th March, 1887, is valuable:—

“In reply to a question as to the best form in which to ship mimosa (wattle) bark, we beg to state that the trade, as a rule, prefer it ground, so long as they can be sure it is not adulterated. Some few, however, cannot be satisfied unless they grind it themselves. We should recommend shipments of well ground, with a few parcels chopped or crushed in bags, but as we know that freight is heavier on the latter, and buyers expect a reduction of from 10s. to 20s. per ton to cover cost of grinding, the former will generally be most satisfactory to shippers. We think that the strength is better preserved in the chopped than in the ground, but there is nothing we can suggest as an improvement on the best standard marks of Adelaide ground. If shipments of chopped be made, it should on no account be shot loose in the ship's hold.”

Barks are sent into commerce in one or more of four forms:—

  • 1. In the bundle.
  • 2. Chopped, i.e., into pieces a few inches in length.
  • 3. Ground, forming a substance something like “tow;” and
  • 4. Powdered, that is of course, if the bark is not too fibrous to permit of this being done. It is not desirable to push the process of grinding too far, as wattle-bark is no exception to the generality of powders, in forming “balls” when thrown into water when too finely ground.

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The preparation of extracts causes an immense saving in freight, but an extract is chiefly valuable in that it enables us to utilize everything. The following is an account of a process as carried on in South Australia a few years back, and is suggestive:—“Messrs. Barrow and Haycroft have established, at Echunga, a manufactory of tannage, which, from the methods employed, is almost pharmaceutical. About 10,000 tons of wattle-bark are sent annually from South Australia alone, and it is calculated that the waste in stripping is about four times this amount. The new factory converts the branches, too small to pay for stripping, into a strong fluid extract called tannage, which contains water 60 per cent., and soluble tannin 38·2 per cent., according to an analysis by Mr. G. H. Hodgson of samples from the first 80 tons recently shipped to England. The wattle ‘trash’ yields 12 to 16 per cent. of tannage. Two men can often cat and load 5 tons, and the waggons can bring in two loads a day, equal to 5 or 6 tons; and at the price (£1 a ton) which the firm is paying for thinnings and tops and branches, so much is offering that the patentees are obliged to distribute their order. The trash is tied up in large bundles and carted into the factory. It is there weighed, close beside the machine which cuts it up into ‘chaff.’ This machine is very much like an ordinary steam-plane, the chisels revolving at a high speed, and cutting through 2½-inch saplings quite readily. The chips are shovelled into large wooden hoppers, into which steam is introduced from a large Cornish boiler. There are three steam-heated vats, and the liquor is transferred from one to the other, pumped into elevated tanks, and thence allowed to flow from a tap on to steam-heated evaporating pans, about 30 or 40 feet in length. The evaporation is so rapid that in traversing the pans from the one end to the other the liquid is converted into a thick, tenacious, treacly extract. At the end of the pans it flows into a cistern, and thence by a kind of treacle-gate into the casks, each of which will hold about 10 cwt. All that now remains to be done is paste on a label, put in a bung, weigh the cask, and send it off to market. In the process of evaporation a certain portion of the tannic acid is destroyed. The plant can be easily moved from place to place. It does not pay to cart the trash far, but a few square miles of wattle country will keep a factory going. The utilization of thinnings allows the cultivation of the tree thickly on waste ground, and to begin cutting the third year. European tanners are quite accustomed to the use of such extracts, but it is said that it will be very hard to introduce it into the colonial tanneries.”—(Chemist and Druggist, 1886.)

I believe that these works are now working with diminished output, as the extract was found to contain too much mucilage, and therefore did not find favour with the tanners. Wattles are rich in gum and mucilage, and some cheap process, which will get rid of these substances and leave the tannic acid uninjured, is a desideratum.

The preparation of wattle-bark extract is no new thing.

“The first shipment of tanning was made from Sydney to England as far back as 1823, in the shape of an extract of the bark of two species of mimosa (Acacia), which was readily purchased by the tanners at the rate of £50 per ton. One ton of bark had produced 4 cwt. of extract of the consistency of tar.note

“In 1843, 3,078 tons of mimosa bark were shipped from Port Phillip to Great Britain. The price then realized in the London market was £12 to

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£14 per ton, but it has since (1854) declined to £8 a ton. The price of chopped mimosa bark in Australia, for export, at the close of 1846, was £2 5s. a ton. Bark valued at £912 was exported from Van Diemen's Land in 1848.

“The imports of mimosa bark have only been to a limited extent within the last few years, reaching 350 tons in 1850, against 110 tons in 1849, 230 tons in 1848, and 600 tons in 1847. The prices realized were £10 to £11 for chopped, £12 to £12 10s. for ground, and £8 to £9 per ton for unchopped bark. Whilst the imports were 3,900 tons in 1844, they dwindled to less than 400 tons in 1850. (Simmonds' “Commercial Products of the Vegetable Kingdom,” 1854.)

In the instructions given (1821) by the Admiralty to Sir James Ross, when proceeding on his Antarctic expedition, his attention was particularly drawn to the astringent substances adapted for tanning, and to the various extracts of barks, &c., imported into England from the Australian Colonies, and which are employed by the tanner.

The quotations I have made have not historical interest merely; they show how in time past as well as now, distant countries have been only too glad to get our wattle-bark, but local requirements must first be met, and since we have abundance of hides, the value of an abundant supply of wattle-bark to the Australian Colonies can scarcely be overrated.