Australian Wool Textile Research (continued)

At Melbourne, two processes[10] had been developed for recovering wool from sheepskin pieces and broken skins. They yielded much better products than the traditional procedure which caused considerable damage and discolouration to the wool. One of them, which was based on controlled bacterial digestion, was an inexpensive process and therefore widely applied in Australia and overseas. In some instances, the quality of recovered wool and its auction price were equal to those of shorn wool.

A problem that had been of concern to the wool industry for decades was the removal of sheep branding products from raw wool. This was near to solution when, in 1950, the Geelong laboratory released a formula[11] for a sheep-branding fluid based on lanolin, designated LBE (lanolin-based emulsion). Until this time, all types of materials, ranging from paint to sump oil and tar, had been used by farmers to identify their sheep. These products had quite significant cost disadvantages, both in discounting to the farmer for the contaminated wool and in the subsequent manual removal of the 'stained' fibres at various stages in processing. These losses were estimated to be at least $3 million[12] in the early 1950s, or 2 per cent (worth about $40 million in 1983/84) of the total value of the clip. Provided it was applied as recommended, LBE was scourable, so the losses were avoided. Not surprisingly, it was quickly adopted by industry.

LBE, however, was not perfect, needing several hours to dry on the sheep, otherwise it would run if there were immediate rainfall. Further research eventually led in 1954 to a new, improved formulation, and this was released as Si-Ro-Mark.[13]

LBE had not been registered as a trade mark, and some manufacturers had introduced their own 'improvements', with dire effects. To ensure that the recommended directions were followed, CSIRO registered Si-Ro-Mark as a certification mark. There were 20 licensees in the first year, and each licence was subject to initial and follow-up tests by CSIRO. Some States introduced legislation making the use of Si-Ro-Mark compulsory but, even without this, manufacturers had ceased making the older fluids voluntarily.

Si-Ro-Mark is still manufactured today, with a production averaging over 400,000 litres per annum over the past decade. In hindsight, it was a relatively simple idea (utilising a by-product of wool scouring (lanolin) as a medium for light-stable pigments), yet the requirement was for a very delicate balance between scourability and durability under sometimes severe weather conditions. It is heartening to note that the cost savings accruing to the wool industry through this one development have paid many times over for the total investment made in Australian wool textile research.

Although over the previous century wool scouring had progressed from river washing to continuous operation, at that time not much was known about the science underlying the process. These were days before the widespread use of synthetic detergents, and the scouring medium was water containing soap and soda. Similarly, while the value of wool wax had long been appreciated, techniques for its removal from the waste scouring liquors and for its subsequent processing were by no means optimised.

The mechanics of scouring were relatively simple (Fig. 13). The wool -immersed in scouring liquor -was moved through a series of bowls, typically of about 8000 litres each, by long-tyned rakes. Greasy wool was delivered by a feed hopper into the first bowl which contained the soap-and-soda liquor at a temperature hot enough to melt the grease. The wool progressed through the bowl by mechanical action, arriving at the delivery end after one or two minutes, where it was mechanically lifted to a pair of squeeze rollers. From there it was fed to the second bowl. This also contained similar soap solution to the first bowl. Subsequent bowls were water rinses, and after the final bowl (the fourth or fifth) the wool went to a dryer. Liquor flowed counter to the direction of travel of the wool, compensating for the abstraction of water by the scoured wool, as well as for the liquor carried away with the effluent.

13 A typical scouring bowl of the 1950s. The machine normally comprised four or five cast iron bowls, fitted with perforated false bottoms and separated squeeze rollers. After the machine has been filled with the scouring liquor and raised to the appropriate temperature the wool is fed into the first compartment on a short brattice A. It is conveyed over a false bottom by the reciprocating movement of a harrow B. the forks attached to the harrow move as a group and are operated by a combination of cams and cranks so that the wool is advanced about one foot during each forward movement. The forks are then lifted out to move backwards to the original position ready to repeat the cycle. the solid dirt is detached in the first bowl and falls through the perforations in the false bottom C into a trough from which it is continuously removed. There is a channel at the base in which a shaft D fitted with spiral fins rotates, bringing the sludge to a central point where it can be discharged automatically through outlet valves. The liquor removed from the first bowl is replenished by a counterflow system.

Australian Academy of Technological Sciences and Engineering