The Future for Domestic Wool

Harold P. Lundgren, Kenneth J. Palmer.

The United States produced 426,200,000 pounds of wool in 1939 and only 258,600,000 pounds in 1949. There are several reasons for the decline, but they do not alter the seriousness of the situation, especially in a time when we are faced with a growing demand for wool for our national defense.

During the past decade our production of wool has been increasingly threatened by the continuing development of synthetic fibers, which are the result of intensive research aimed to meet new demands, new fashions, and lower costs. By contrast, the costs of producing and processing wool have gone steadily up, and comparatively little progress has been made in streamlining the traditional rule-of-thumb procedures. For example, the wage cost of producing a wool textile fabric in 1950 was approximately double what it was in 1941.

We want to keep our wool industry vigorous because wool is essential to our national health and security; the Armed Forces consider wool a strategic and essential material. Domestic wool production, even in peacetime, has never been equal to consumption. Normally we produce only from one-fourth to one-third of our total requirements. To meet any emergency we should produce at least two-thirds of our normal requirements of apparel wool.

The problems before us are : How are we to develop the wool industry to keep pace with developments in other industries? How make sheep production and the marketing and processing of wool more efficient? How improve the quality of domestic wools and the spinnability of the medium grades to satisfy the increasing demand for worsted yarns? Can we find ways to impart new properties to wool to increase its usefulness?

Although wool meets many demands in quality ( notably its warmth, excellent resilience, and felting power), it has a number of weaknesses. Its lack of resistance to hot water and its vulnerability to micro-organisms and moths are well known. Its instability to alkalies, acids, and steam used in processing is encountered by the textile processor. From the chemical point of view, these weaknesses are the evidence that wool is itself a reactive chemical substance. The acids, alkalies, and steam react chemically with the wool structure to result in harshness, reduced wearlife, and lower strength of the fiber. But wool can be improved and its processes streamlined. It is entirely possible--through investigation of the chemical nature of wool, including its stability to chemical environments and its reactions with the host of new chemical agents to find a means of stabilizing wool to deleterious environments and to impart new properties of practical significance. Such developments would provide the basis on which to convert present empirical methods in the wool industry to efficient modern practice.

Working together to find the answers are the Production and Marketing Administration and the Agricultural Research Administration, of the Department of Agriculture, and several State agricultural experiment stations. An example of the cooperative work on wool is a project for improving the spinning qualities of the medium grades, which is supported by the Department of Agriculture and carried out by the Textile Research Institute in Princeton, N. J. The American Wool Council, the International Wool Secretariat, and wool growers here and abroad also sponsor the investigations. The Forstmann Woolen Company is under subcontract to process the wools for the project. The Western Regional Research Laboratory assists in mechanical and microscopic characterization of the wools. Scientists of the Bureau of Human Nutrition and Home Economics study the properties of the fabrics made from the wools.

TO THE CHEMIST, wool is an assemblage of molecules admirably suited for particular purposes. Because of its unique architectural design, wool is strong and yields to stress in a desirable manner. Basically, its molecular properties determine all its characteristics--moisture-absorbing property, felting behavior, affinity for dyes, draping qualities, and luster. Because wool can be modified chemically, the chemist disagrees with those who maintain that wool, being a product of nature, cannot be improved. It is true that wool possesses certain features, such as felting property, which the chemist has failed to reproduce in synthetics.

The application of chemistry to wool begins on the farm. The presence or absence of certain minerals can profoundly affect the quality of wool. A copper deficiency in the diet of sheep makes the wool stiff and steely and a cobalt deficiency also makes it markedly abnormal. The soil in certain areas, northern Wisconsin, for example, is deficient in cobalt. In some areas, as around Bakersfield in California, there is too much molybdenum in the soil and forage. An excess of that mineral in the diet of sheep causes the wool to lose its natural crimp. The wool from black sheep turns white when the diet contains too much molybdenum.

Alternate high and low amounts of molybdenum in the diet give corresponding white- and black-ribbed wool.

The chemical environment can also affect wool quality directly. Sheep that are kept in regions rich in alkali yield an inferior "alkalied wool," which is practically worthless. Sunlight, particularly in humid regions, can cause photochemical damage to the exposed tips of wool. Wool that is so damaged often takes dyes unevenly. Fortunately, chemists have learned to overcome the fault somewhat by treating the wool before dyeing.

Among the several unknowns of wool is why wools from Australia tend to be whiter after cleaning than do domestic wools. The problem is receiving increasing attention because of the greater use of light and pastel shades in fabrics.

The effects of a sheep's diet and environment on the quality of its wool are being studied at several State agricultural experiment stations and the Bureau of Animal Industry. The goal is practical information that will help the grower determine which feeds, environment, and breeds of sheep in specific areas will produce wools of maximum quality.

SEVERAL PROCESSES that involve chemical principles come between the shipping of wool and the time it is ready as a fabric. One of the first is the removal of contaminating grease, dirt, dried sweat, fecal matter, dried urine, and burs. Contaminants constitute 40 to 70 percent of the total weight. The farmer who sells his wool is paid on the basis of the yield of clean, scoured wool. What happens later may appear to be of little concern to him. Actually it is important to him that the costs of scouring and the other steps be reduced so that wool may better meet the competition of other fibers.

The chemist sees several possibilities for reducing scouring costs. First is the recovery of potentially valuable chemical constituents from the wool grease.

A second is to make more efficient the process, which for ages past has been largely done in the same manner by washing the wool with water mixtures of soap and soda. A small quantity of wool in this country is scoured by the more expensive method of extraction by solvents. This method has the advantage of easy recovery of the potentially valuable constituents of grease. However, chemists now are finding it possible to recover economically the grease from the soap liquors.

Chemical research is also throwing new light on the action of soaps. New types of soap and other detergents, with more efficient washing power for specific purposes, are being discovered. Just why soda makes the washing by soap so much more effective is being studied. Actually soda is undesirable to the extent that it is alkaline and, unless used with caution, has a deleterious effect on the quality of wool. To streamline the soap-soda method, chemists at the Western Regional Research Laboratory are studying the mechanism of the action of soap and soda in cleaning wool. One outcome of the research is the finding that certain nonalkalme agents are effective so effective, in fact, that scouring can be accomplished with only the natural soap present in the wool contaminants. These soaplike constituents are the dried perspiration, the so-called suint, which comprises as much as 30 to 40 percent of the contaminating impurities. It has been recognized for a long time that these suint salts might be effective for scouring. Europeans have used a process in which clarified water extracts of grease wool are used for grease removal. The process is not efficient.

The Chinese found that the recovery of grease by the water extracts is greatly improved when pig dung or urine is added. Recent laboratory findings support that discovery. The scouring efficiency of the neutral soaps in the suint is markedly improved when small quantities of certain chemicals, such as ordinary alcohols, are present,together with small quantities of table salt.

The findings are still on a laboratory scale and must be tested commercially before their practical value can be determined. No doubt they will be significant in the further improvement of the wool-scouring procedure. The ultimate aim of the research is the development of methods to give the best overall economy of scouring and recovery of valuable grease constituents, without damaging the wool fiber too much.

Wool undergoes many manipulations in processing. One of the most critical is spinning and preparation for spinning. Offhand, we might not expect chemical principles to be involved in such mechanical processes as carding and spinning, but when we look more closely into the matter we find that they are.

The characteristics of wool its toughness, its spinnability depend ultimately on its structure, both the large structural units that we can see under the microscope and the molecular structure of those units. When we look at wool under an ordinary microscope we find that the surface has scales not unlike the shingles on a roof. The scales are about 4/100,000 of an inch thick and overlap one another in irregular fashion. Because the exposed edges of the scales point in one direction, the frictional resistance to rubbing differs in the two directions along the fiber. This difference in frictional behavior accounts to a large degree for wool's unique felting property.

Under much higher magnifications, as under an electron microscope, the scales themselves appear to be covered by an exceedingly thin membrane, called the epicuticle. The epicuticular layer might have an important role in the dyeing of wool by limiting the rates of dye penetration.

Beneath the scales is another membranous layer. This layer surrounds the cortex which makes up the bulk of the fiber. The cortex consists of elongated cells, the so-called spindle cells, which are approximately 4/1,000 of an inch long and about one-tenth as wide as they are long. The spindle cells are simply bundles of long, thin fibrils bonded together with a cementing material that is believed to have the same chemical composition as the rest of the wool constituents in the cortex.

Some wool fibers have an inside core of porous structure, the medulla, but it appears to have a minor effect on the physical and chemical behavior of wool. The response of wool to stretching is conditioned by the slippage of the scales and spindle cells, past one another, and ultimately by the slippage of the molecules comprising them.