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The New Zealand Railways Magazine, Volume 10, Issue 7 (October 1, 1935)

The Kauri Gum Industry

page 43

The Kauri Gum Industry.

Not merely because it is peculiar to this country, but also because of the very definite flavour of romance which invests the activities of the lonehand gum digger, the kaurigum industry is probably the most interesting in New Zealand.

Kauri-gum is the matured resin of the kauri-tree (Agathis australis), the largest tree in the world, the habitat of which is confined to the Auckland Province. There are two essential varieties of gum, the most valuable of which is fossil resin, dug out of swamps which mark the sites of buried kauri forests. As is well known, the common method of locating gum below the surface of the ground is to probe with light, slender steel spears, which vary in length from a few feet to twenty-four feet. The experienced digger has little difficulty in differentiating between gum and any other hard substance struck by his spear, the “feel” of the blow telling him at once whether he has located a find or not. Of late years machinery has been used with some success, and improved systems (such as “close paddocking” and various washing processes) have superseded to some extent the haphazard methods of the old-time digger; however, progress in this connection has not been made to the extent which one would imagine.

The bleakness and desolation of a gumfield must be seen to be believed; in the first place, the soil is, without exception, poor, consisting mainly of white clay or yellow sandstone, with black peat predominating in the swamps; the only vegetation which appears to be able to wrest an existence from the soil is manuka, fern and rushes. The ground is pitted with holes made by the diggers, whose shanties of timber, sods and corrugated iron add little beauty to the landscape. The greatest extraction of gum takes place during the summer and autumn months—i.e., from December to May.

Besides fossil resin, an appreciable amount of gum is obtained from the living kauri tree by the process of “bleeding” or “tapping,” which is identical with that used in the extraction of resin and turpentine from coniferous trees in the U.S.A. and other countries. “V”-shaped cuts are made in the bark of the tree, horizontally across the barrel. The cut is called the “tap” and is deepest at the apex, where it almost reaches the sap wood. Taps are cut across the limbs and barrel of the tree, and are spaced eighteen inches horizontally, the interval between such rings of taps being about six feet. The gum is then harvested every six months. There are two systems of tapping; in the first case the forests are leased for bleeding purposes shortly before being cut, with the stipulation that no taps are to be made in the barrel of the tree; in the second case the trees are tapped and bled from head to foot. The first system is called “bleeding heads only,” the latter “bleeding heads and barrels.” The gum obtained from the living tree, however, is not nearly as valuable as fossil resin.

Although to the uninitiated there is little difference to be discerned between one heap of raw gum and another, no fewer than thirty-three classes and sub-classes were defined by the Kauri Gum Commission, in 1921. These were based primarily on a division into four main classes, depending partly on colour and partly on origin—viz., white gum (ranging from “dial” or “bright gum” to “diggers’ dust”); white swamp gum (“bold—with heart” to “dust”); black gum (“rescraped” to “washed dust”); and bush gum (“rescraped limb bush” to “bled bush”). The harder, paler and more transparent gums yield a clearer and more valuable product than the sugary or dark gums, so that commercial preference is in favour of the former, and their value is correspondingly high.

Maoris on the kauri gum fields, North Auckland, New Zealand. (Rly. Publicity photo).

Maoris on the kauri gum fields, North Auckland, New Zealand. (Rly. Publicity photo).

In literature, the first mention of kauri-gum appears in the Journal of Captain Cook for the 16th November, 1769; but although it was again noted during the next few years by M. M. Monneron, L'Horne and Du Clesmeur, its commercial value was not generally known for over 70 years; as late as 1841 Governor Hobson made no mention of it as a possible article of export, but by 1845 a brisk trade in the commodity had sprung up. At first it was used in the manufacture of sealing wax, and then as a stiffener for high-class candles; later it was employed for the adulteration of shellac. However, it was not until the gum was found extremely suitable for the manufacture of high-class varnishes, that the trade assumed sizeable dimensions. The lower grades are used at the present time in the manufacture of linoleums.

Up till 1865 the actual collection of the gum was restricted almost solely to the Maoris, the only gum gathered by the Europeans being obtained by settlers who unearthed it in the course of ploughing. For many years the finest grades of gum were abundant in large masses on the surface of the ground, but in time this surface gum disappeared, and resort was made to the buried gum. The first gumfield thus opened was at Papakura, the next at Henderson's Mill, and the next at Riverhead, all within a twenty-mile radius of the City of Auckland. About 1891, Austrians from Dalmatia and adjacent Slav provinces entered into competition with the colonials and page 44 Maoris, and, although in 1898, legislation was enacted to exclude aliens from extensive tracts (some quarter of a million acres) of gum lands, these men to-day still dominate the industry.

For the first 40 years the diggers produced only gum of good quality—white “range gum” (i.e., from the hillsides and claylands) and every lump had to be most carefully scraped to remove any encrusted dirt or outside coating of gum of inferior quality. About 1885 the first “black gum” came on the market, and commanded a price of £1 per cwt. “It was hard, solid black of the best quality, showing none of the softer ‘streak’ which characterises so much of the present output of black.” With the steadily increasing demand for kauri-gum, however, the exploitation of even less valuable grades, such as “washed nuts,” “chips” and “dust” became profitable. Soft gums of poor grade, variously termed “sugar,” “chalk” or “sooge-sooge” by the diggers, many thousands of tons of which had been burned and wasted, began to command a fair price. The peak was reached in 1922, when the average price obtained for gum was no less than £98, as compared with the £4/10/0 obtained for the finest gum in 1847. The greatest export in any one year was 11,116 tons, in 1899. Up to the close of last year, the total value of gum exported amounted to an aggregate of no less than £22,000,000.

As to the future of the industry, the outlook is not, at the moment, particularly bright. Kauri gum is not the only fossil resin used in the production of varnish; other competing resins are animi, copal (of various kinds) and manila. The most serious competitor of all, however, is China wood-oil, an extract from the nut of the tung tree. Although a good demand still exists for the poorer grades of gum, the increasing competition has had a deleterious effect on sales of the better grades to manufacturers of lacquer and varnish. It was reported recently, however, that during a visit by the Prime Minister (the Rt. Hon. G. W. Forbes) to the British Research Association, the director, Dr. Jordan, stated that kauri-gum, produced by a new solvent process, undoubtedly had a future as a standardised material in the paint, varnish, lacquer and linoleum industries, and that commercial production along the special lines indicated should be established as soon as possible. Developments in this connection will be watched with interest in this country, particularly by gum diggers of the North.