From the Tropics

Hawke's Bay Herald-Tribune, Issue 51, 16 March 1937, Page 13

From the Tropics

Delicate Timber and its Problems

T?ROM the Baltic comes wood oi the 1 ptoe— the xed deal known to the builder. From within our own shores, from America, Europe and Japan comes the oak, so prized for strength and beauty (writes Dr. F. Y. Henderson in the Manchester Guardian). But from the tropics come the exotic woods, light and dark, the source of some of our most beautiful decorative woodwork. It is in the sphere of decorative work that timber remains unchallenged, ahd there is no material which is its serious competitor in panelling and similar uses, as no other material possesses the same beauty of figure and colour. Particularly, ifc is from the so-called hardwoods obtained from broad-leaved trees like oak, walnut and mahogany that the flnest figured timber comes, whether used in the solid or as a veneer upon some other wood, but the number of new species in use Increases every year as the resources of Ihe tropics are discovered and their beauty exploifced. * • • T>UT it is a far cry from the tropical D f0rest to the flnished panel, and even a brief accoimt of the vicissifcudes passed through and the calamities avoided in the brlnging of a log to England reads like a chapter from the "Odyssey." To begin with, the fact that the tree exists at alh a flourishing member of a dense and overcrowded tropical forest, discloses a history of successful campaign against competitors in the struggle for light and nourishment, against enemies and disease — a campaign carried on, mayb'e, for three or four hundred years before the tree is big enough to attract the eye of the forester and to be marked for extraction. The unsuccessful have gone down before the attack of burrowing beetles, which destroy the growing and sap-con-ducting regions of the inner bark, or wood-destroying fungl, which, entering perhaps, through some insignificant wound caused by wind or antaal, rot the heart of the tree and- ulttaately kill it. Before it has been felled, then, a tropical tree has had the possibility of troubles enough, but those to come are worse, for the tree once felled is defenceless and can neither put up resistance nor effect repairs. It is then, in fact, ' nothing more than a mass, however taposing, oi alowly dying vegetation. * * * YLTHIIiE lying on the ground it is particularly susceptible to the attacks of two kinds of beetles, the long-horned beetles and the pin-hole borers. The ship-worm is the worst enemy of the floating log: it is a relatioa of the

mussel and or taae common soau, du* jo has a long round indiarubber-like body, commonly about eighteea inches long and half an inch thick, armed at one end with a pair of shell-like gnawing organs, which it uses to honeycomb the timber with large tunnels, in which it lives. Ifc is fond of clear, warm seawater, and quickly attacks submerged or floating timber. Its name is explanatory enough, and we know that it caused great damage to ships even in Colombus's time. Once on board shlp and stowed away in the holds— if these are properly ventilafced— the timber is safe until it is ipiloaded at the home porfc. Bufc if the ventilation is poor and the air is not permitted to circulate properly a stagnant condition of the atmosphere soon develops, and the damp logs are- open to attack by a fresh group of enemies — those fungi which infest damp timber. ♦ • • rpnERE are three groups of fungi con- •*- cerned, and any or all of these may begin to grow on the log: those which form moulds, those which stain the timber internallx, and those which actually destroy the wood itself. The moulds are those same organisms which cause the familiar white and green mould of jam and the like, and in fact they do not actually damage the timber. But they render the logs unsightly, and a prospective buyer may rightly deduce that if the timber has been kept damp enough to allow these moulds to form, then other and more dangerous fungi may have gained a footing. • * ♦ npHE logs after delivery to the yard are sawn up into thick planks or they may at once be made into veneers. The timber is now stacked in piles for seasoning, and this seasoning or gradual dry-ing-out must be carefully watched, for if it be too slow stain or decay will likely develop in the wood, and if it be too fast the unequal rate of drying of the inner and outer portions of the log will cause serious "shakes" or splits to occur, with a consequent loss of good ttaber and of money. Usually, however, with care, and after perhaps two or three years of slow evaporation, the proportion of water in the wood has fallen to .about 20 per cent., and the large planks are now taken to the kiln, perhaps after having been resawB to smaller sizes. The last operation to which the timber is subjected before its final shaping is that of kiln drying. The percentage oi moisture left in a ttaber even after Iona air-seasoning is too high for the safo use of the wood in a building, particularly if the building is cent-rally hea-ted