DAMAGE TO WOOL GARMENTS

Press, Volume LXXIV, Issue 22437, 25 June 1938, Page 15

DAMAGE TO WOOL GARMENTS

BACTERIA PROVED TO BE CAUSE PREVENTION METHODS DISCUSSED WORK OF DUNEDIN SCIENTISTS Investigation of some complaints about deterioration of wool garments has been made by the New Zealand Wool Manufacturers’ Research Association at laboratories in Dunedin. The cause of the damage has been found by Dr. C. E. Hercus, Professor of Bacteriology and Dean of the Medical School, to be bacteria, and work on chemical substances to prevent bacterial attack is now being carried out by the association’s research chemists.

“Until bacterial growth occurs the wool cannot be attacked,” said Dr. Hercus in an interview with “The Press” after a meeting of the association last week, when the experiments conducted so far were explained. “The wool fibre is an insoluble and unreactive substance and so cannot at this stage support bacterial growth, the most important requirement of which, experimentally and technically, are soluble nitrogenous organic substances. In used garments this factor is supplied by the body secretions, particularly perspiration. Under manufacturing conditions the soluble organic substances may be derived from the suinf naturally present, from decomposition of the wool constituents during processing, or from organic substances in the various solutions employed, either accidentally present or purposely introduced. A high humiditv, a high temperature, and an alkaline reaction all favour bacterial growth. “Theoretically, bacterial growth does not always result in damage to the wool fibre.' In practice, bacteria ca'pable of causing damage are always present in large numbers on the wool fibre and its surroundings, and in the dust which settles on them, so that conditions allowing bacterial growth result in damage to the fibres. Bacteria capable of attacking wool can only be eliminated and excluded in experiments conducted with bacteriological technique.” Action of Bacteria, The bacteria grow alongside the wool fibres and exert no mechanical action on the fibre. They can affect it only by liberating chemical substances, called proteolytic enzymes, which diffuse to the fibre and act upon it. They act first on the cementing substances which bind the constituent cells of the wool fibre. This results, first, in a loosening of the scales which cover the surface. As the action proceeds, the cortical cells, which make up the bulk of the fibre, are loosened and the fibre falls apart. The broken end of such a fibre shows microscopically a “brush” appearance; like the frayed ends of a rope. The cause of the damage was investigated over a period of years on garments submitted to Dr. Hercus. The human skin is a suitable medium for bacteria to grow upon, because the perspiration, secreted continuously, provides the necessary moisture and food material.

Experiments with Clothing On the other hand, in the experiment on singlets done at the Medical School, it was found that as long as these were kept reasonably clean there was no sign of damage that could be definitely attributed to bacteria. Felting occurred at the aimhole, but this was to be expected, because of the rubbing of the damp garment on the skin. When singlets were worn for tennis and then left lying about dirty, bacterial attack was apparent. Some interesting work was done on damaged bathing costumes returned from the baths at Rotorua. At first it was thought that the water of the hot pools might have had a deleterious effect on the wool. However, an examination of the costumes proved bacterial attack. Evidently the costumes were stored or left lying about damp, and this, combined with the high summer temperature, caused the damage. Improper treatment of the garment possibly explained the rapid deterioration of other bathing costumes returned to the manufacturers with complaints of holes appearing alter a few weeks or months of wear, the researchers consider. Instead of being well rinsed and dried as soon as the swimmer came out of the water, the costume was worn for sun-bathing; and the warm, damp wool then made an excellent incubating ground lor the bacteria of the skin. Treatment of Fibre “It might be expected that some treatment could be found which would make the wool fibre more durable and resistant to enzyme action, in the same way that the tanning of greenhide results in the more durable leather,” stated Dr. Hercus, who has carried out the bacteriological research for the association, which is directed by Dr. F. G. Soper, Professor of Chemistry in • the University of Otago, with Mr H. V. Peryman as chemist. “We have studied the action of formaldehyde and of chroming. It was found by the association that formaldehyde entered into combination with the wool, but the resultant fibre showed no increased resistance to bacterial or moth attack. Chroming showed a relative resistance to bacterial attack. It is uncertain whether this Is due to an increased resistance of the fibres to enzyme action or whether the relative immunity is entirely due to a lessening of the amount of water soluble substances which are necessary for bacterial growth. Another method directed to increase the resistance to attack is processing so as to retain as far as possible the natural resistance of the .wool fibre. It has been found that drastic chemical treatments, such as peroxide treatment and chlorination, produce a permanent damage which renders the wool more susceptible to bacterial attack. Exposure to ultra violet radiation produces a susceptibility which is removed by washing. It appears that chemical damage does not necessarily result in increased susceptibility. Chemical substances are now to be tested by the association with special reference to New Zealand needs. Most of the work done abroad on antiseptics for textiles has been directed towards the prevention ot mould growth and an antiseptic that is strongly toxic to moulds may have little effect on bacteria, the Dunedin research workers report.