KAURI GUM

KAURI GUM

by Jeanne Hannington Goulding, Botanist's Assistant, Auckland Museum.

KAURI GUM

Kauri gum is formed when resin exudes from a crack in the bark of the kauri (Agathis australis) and hardens on exposure to air. Pieces of various sizes, some weighing several pounds, collect in the axils of the branches and in the debris at the base of the tree. The colour of the gum ranges from pale yellow to reddish-brown and even black. Fossilised gum is harder, and usually paler and more translucent than that found in living forests. Buried at various depths, fossilised gum has been found on sites of long-extinct kauri forests. In the Auckland area it has appeared in strata older than the local volcanic rock. It is obtained north of 38° latitude, under lake beds, swamps, and sand dunes, as well as from higher ground. The discovery of two or three layers of gum in the gum-fields of the north indicates that a succession of kauri forests had flourished and disappeared centuries ago, each leaving its quota of gum buried at different depths.

Captain Cook in 1769 must have seen kauri gum on the beach at Mercury Bay, although he wrote in his Journal that the resinous substance he found there came from the mangrove trees. In 1819 Samuel Marsden reported pieces of gum lying on the ground near Ohaeawai, the site of intensive gum-digging 50 years later.

Maori Uses

Before the European settlers came to New Zealand, the Maori had several uses for kauri gum, which he collected from the surface of the ground. It made good fuel, and was also carried alight as a torch. The soot from the burnt gum was used in the tattooing process. Fresh gum was chewed, and sometimes softened by heating before becoming “chewing gum”.

Early Export Trade

A small cargo of kauri gum arrived at Sydney in the schooner Brothers in 1815. The early traders exchanged nails and blankets for kits of surface gum collected by the Maoris. Edward Markham, walking from Hokianga to Kerikeri in 1834, saw lumps of kauri gum, and recorded in his Journal that “it requires so much oil to make it soft, so as to be able to pay the bottom of a Boat, or do the Outside of a House with it as renders it nearly useless”. Charles Darwin, writing about his visit to Waimate in 1835, said that kauri resin “is sold at a penny a pound to the Americans, but its use is kept secret”. It is claimed that James Busby and Gilbert Mair were the first to export gum to America about 1838. The Auckland firm of Brown and Campbell made early shipments to England (1844 or 1845). In 1848 kauri gum dissolved in “Oil of Wood” was mixed in paint – presumably for ships – at Hokianga. It was recognised overseas as a suitable resin for manufacture of a slow-drying varnish with a hard finish. In 1853, 829 tons of gum were exported, and over 4,000 tons, averaging £40 a ton, went overseas in 1870.

Gum-digging

When all the kauri gum lying on top of the ground had been collected, Maoris and Europeans began to dig up the big lumps near the surface. Spades were the first implements of the gum-diggers; then the spear and hook were devised. The “gum-spear” was a long steel rod, tapering from one quarter of an inch thickness to a sharp point – the rod attached to a spade handle. An improved model, which went into the ground more easily, had a coil of fine wire fixed above the point. The “hook” – also fitted with a spade handle – was a length of inch piping with a steel hook welded on to the bottom of it. It was used to hook up the lumps of gum located by the spear. The spear and hook were particularly useful in swamps. A pikau, or sack, for carrying gum, completed the “tools of trade” of the early gumdigger. In 1885 about 2,000 diggers were at work, mainly in areas north of Auckland, although the best gum came from the Coromandel Peninsula. British subjects were able to procure licences (5s. a year) to dig on kauri gum reserves; private land owners charged £1 or more. Storekeepers who owned gumland insisted that gum dug from their land be sold to them or bartered for stores. The diggers scraped and sorted the gum. The highest export for any year was reached in 1899, with 11,116 tons.

By 1900, hundreds of Dalmatians – immigrants from Europe – were on the gumfields. They camped together in groups, digging the swamps in summer and the hills in winter. An increasing demand for poorer grades of gum, used in making linoleum, made it profitable to search for smaller gum: “nuts”, “chips”, “seeds”, and “dust”.

Mining for Gum

A primitive apparatus, used in 1915, to extract fragments of gum from the soil, consisted of an iron tank with a perforated base, and a paddle on a shaft in the centre. Gum-bearing soil was shovelled into the tank, water poured in, and the paddle worked by hand until most of the soil had broken up and passed through the holes in the bottom of the tank. The remaining material was thrown into a heap, dried and hand-winnowed, to remove any fibrous matter, and the gum collected. Subsequently more elaborate forms of this “hurdy-gurdy” were used. A large machine was designed by C. Suttie to work swamp material, and was used near Dargaville. At Poroporo a steam plant was employed, and near Awanui a dredging plant installed. The vacuum-salt process, invented by J. S. Maclaurin, was recommended by the Kauri Gum Commission in 1921 as being the most efficient method evolved to remove dirt and foreign matter from kauri gum.

Gum from the Living Trees

Gum was collected from the living kauris where it had lodged high up in the branches. There was a time when “bleeding” was practised too. Armed with climbing hooks, spiked boots, ropes, and tomahawks, men would climb the trees and cut V-shaped “taps”, 18 in. apart round the barrel of the tree at intervals of about 6 ft. The exuded gum was harvested every six months. “Bleeding” was discontinued in State forests when the Department realised that it was injurious to the trees.

Gumland

The gumlands were generally unsuitable for farming after the diggers had finished. “Potholes” and trenches remained unfilled – “tailings” piled beside them – and the continual burning off of manuka and fern, left nothing but bare clay. Gorse, hakea, and other introduced weeds displaced the stunted manuka, and large areas were useless until modern machinery, lime, and suitable fertilisers were available for land development.

Market and Uses (1900–62)

Although the export price had risen to £61 a ton in 1900, good-quality gum was harder to find, and a market therefore developed for the poorer grades, used in the manufacture of linoleum. Fluctuations in export quantities, rather than prices, were noticeable over the next 20 years. The drop to 4,500 tons exported in 1915 was a result of the restricted European market during the First World War. In 1920 the United States bought 3,244 tons as against the United Kingdom's 2,544 tons, the average value being £86 a ton. Export prices dropped to £25 a ton during the depression of the thirties; and although unprecedented values were reached in the forties (£101 a ton in 1948), demand for gum became less. Quick-drying synthetics had superseded kauri gum in the manufacture of varnish. Substitutes were also used in linoleum manufacture, and low-grade gum failed to interest overseas buyers.

Since 1947, “range” or “pale” gum from high localities has been exported for use in the dental trade. One ton shipped to England in 1962 realised more than £300. This market takes only “bold” gum – clean pieces with the outer coat removed. There has been a revival in the use of “brown” gum, from swamps and low-lying ground, due to a demand from the United Kingdom, U.S.A., Italy, Germany, and Sweden. The last three countries use it in varnish.

The supply of fossilised kauri gum is not exhausted. Lumps are often turned up when new land is developed, and good-quality gum can bring a high price.

In 1961, 91 tons of kauri gum valued at £13,183 were exported; the 1964 exports were 53 tons valued at £11,481.

by Jeanne Hannington Goulding, Botanist's Assistant, Auckland Museum.

  • Diary (typescript), Hobbs, J. (1848)
  • Researches in Geology and Natural History, Darwin, C. (1839)
  • The Gumdigger, Reed, A. H. (1948)
  • New Zealand or Recollections of it, Markham, Edward, McCormick, E. H. (ed.) (1963).

KAURI GUM 22-Apr-09 Jeanne Hannington Goulding, Botanist's Assistant, Auckland Museum.