How Warm Is Wool?
A SCOTSMAN stepped one day into a shop in Edinburgh to buy a new plaid. As he fingered the goods the salesman showed him, the following delightful exchange of frugal syllables took place.
Scotsman: ‘Oo?’
Salesman: ‘Ay, oo.’
Scotsman: ‘Aa oo?’
Salesman: ‘Ay, aa oo.’
Scotsman: ‘Aa ae oo?’
Salesman: ‘Ay, aa ae oo.’
And the Scotsman bought his plaid, satisfied that it was wool, all wool, and all one wool.
Typical of the traditional regard for wool is this story of Scotch caution; indeed, for so long as wool has been known as a textile fibre it has been credited with the possession of unique qualities. Our grandparents believed there was some subtle magic about red wool flannel, for instance, and in that revolutionary period when long winter underwear began to fall into disrepute it was still somehow believed that death by pneumonia lurked in winter wear of anything but wool. Even to-day in the infant-wear department of any store you will hear, repeated again and again like some incantation, ‘A bit of wool over a baby’s chest and tummy!’
Wool, all wool, is worshiped wath a devotion only second in degree to the lack of knowledge as to why it is so worshiped. For, in spite of the general belief that a fabric is warm in direct ratio to its wool content, few consumers could tell why. Even wool manufacturers and retailers are usually at a loss to explain why they too believe it, and seemingly none can prove it.
Against this background of conviction and demand set this strange situation, that for years past there has been a steadily if stealthily increasing substitution for wool in the fabric field. To-day it has reached the point where the very thing the consumer public demands, expects, and usually believes itself to be buying, is among the really scarce commodities. Certain trade experts say they believe that not much more than 20 per cent of the woolen and worsted fabrics being made to-day are all wool, and textile technicians accustomed to testing the annual production from the woolen mills say that in the middle and lower price fabrics there is from 40 to 80 per cent of fibre other than wool. A well-known Boston wool merchant, troubled by this state of affairs, said flatly, ‘We know that as much as 50 per cent of rayon is now going into cloth that is later sold in so-called all-wool suits.’
Plainly this opens up an avenue of serious thought. Winter clothing accounts for a large section of the American family budget, and in many parts of the country it is a very important factor in health and well-being for rich, middle class, and poor. Yet, curiously enough in this presumably civilized and scientific age, the problem of warmth in relation to fibre sources and mixtures is one of the least studied and least understood of all consumer subjects.
The surprising fact is that warmth in a fabric is due, not to any inherent warmth quality of a fibre itself, but rather to the lasting thickness and cellular construction of the cloth. Silk, wool, cotton, or rayon may create fabrics equally warm at the start if of identical thickness and structure. For warmth is largely due to the trapped air held in the cells within a fabric weave; the more intricate the meshing of these fibres, the more air cells — consequently the more air held within the cloth and without motion. A second point is interesting, too. Warmth in a room without air currents is a very different problem from warmth outdoors in a gale. In the first situation the prime necessity for warmth is a fabric with the most possible air cells, to provide insulation against outer cold and a barrier against the escape of bodily heat. Closely meshed spongy weaves, which make layer upon layer of fine cellular insulation and which radiate back upon the human body the heat transferred from it to the fibres without conducting it away and out of the garment, are the ideal type of fabric for indoor warmth. In the open air, with a wind blowing, or in active motion such as skiing, skating, and so forth, there must be, in addition, a windbreaker layer. A close, tight weave — perhaps thin, but highly resistant to air passage — is the thing; a suède or leather jacket or a garment of specially woven cotton may be used. A fur coat, as you may see, offers the trapped air insulation through its thick fur side and windbreaking quality through its pelt. Weight and cost must play a part in the wise selection of the proper fabric for each particular need.
There appear to be three general classes of fabrics with a capacity to trap and hold insulating air for warmth in clothing and blankets. They may be compared in turn to a comb of honey, a loaf of fresh bread, and a sponge. There are fabrics which, like the honeycomb, have a cellular construction, with air trapped and held inside them. But in use — that is, when worn, washed, and ironed — these cells tend to break down rapidly, flattening out and ‘spilling’ the trapped air just as a crushed honeycomb spills its honey; and no more than you can rebuild the broken honeycomb can you rebuild the flattened fibre cells. The second type of fabric resembles the loaf of fresh bread; compress it, and afterward it will push back a little into shape, regaining some of its cellular insulation, but never again its original structure. Finally there is the fabric which, like the sponge, may be flattened in use but immediately or shortly regains its size and shape, the expanding air cells again filling with the insulating air.
It requires no master mind to deduct that the last-named type of fabric must be the warmest in actual use, no matter what the others may be in the store or the laboratory. And the next question obviously is what fibres or combinations of fibres create fabrics of this type.
Although wool fibre has in itself no warmth property, it does have to a unique degree the rare and valuable quality of resiliency, which creates a fabric with the greatest capacity to trap and hold air over the longest period of time under use. Add to this the fact of the peculiar structure of the individual wool fibres which makes for felting or meshing, and there you have the reason for our thousands of years of respect for wool as a warmth provider. No other fibre has these inherent qualities to anything like the same degree. Cotton is like the honeycomb, its cells easily broken down and flattened permanently. When cotton is mixed with wool, the effect is partially nullified, but to no great degree. Silk, while having great natural elasticity and resiliency, does not have the same property of felting. Rayon, in its more familiar form, — that is, as a continuous filament from the spinneret, — has virtually no resiliency and certainly no felting characteristic. Linen cannot be woven into the same constructions as wool to be commercially salable.
But of real importance to consumers is the appearance of a new form of rayon called spun rayon, known to the trade as rayon cut staple. Although known for years as a by-product of rayon, only recently, in this country at least, has it attained major proportions for textile use. In 1935 our consumption of spun rayon was 6,661,000 pounds; in 1936 it was 25,400,000 pounds; and its production and use are still leaping ahead by enormous bounds. Japan is the largest producer of rayon, both in the continuous filament form and in the cut staple form. In 1936 we produced some 12,000,000 pounds of spun rayon ourselves, and imported 14,000,000 pounds, of which half came from Japan; even under the present tariff she has been able to sell her product here at a price with which the domestic rayon producer, much less the wool manufacturer, cannot hope to compete.
Spun rayon is no more than the continuous filament rayon cut into short lengths similar to wool or cotton fibres and spun into yarn, as either wool or cotton is spun. The resulting yarn looks and feels like wool. Fabrics made wholly or partially of it cannot be distinguished from all wool except by experts — and not always then. It creates novel and attractive fabric effects, and, since its production cost is far below that of good wool, it should offer a practical new item in our consumer price structure. But consumers everywhere are asking: Does it behave like wool? Has it the inherent characteristics of wool?
Frankly, wool manufacturers generally do not appear to know. Some are honestly concerned about the situation, but the majority seem to prefer not to know what effect the introduction of spun rayon is having on their woolen goods — perhaps because there is a greater margin of profit in manipulated goods with a concealed rayon content than in the all-wool or wool-and-cotton goods. The wool growers, of course, are disturbed, but the wool manufacturers, especially in the underwear field, have shown small enthusiasm for the current consumer campaign for fibre identification.
The man who has done the most research on the subject, and can best evaluate the worth of spun rayon as a substitute for wool, is Dr. Frederic Bonnet, chief technician of the American Viscose Company, this country’s largest producer of rayon. Dr. Bonnet states frankly that spun rayon in its natural form, untreated, does not have anything like the warmth qualities of wool, at least under consumer use; but he believes that, treated with one of the new resins being evolved to reduce crushing of textile fibres, a fabric of spun rayon may go far toward equaling the qualities of wool.
The resin treatments are now in use for treating rayon velvets in particular, and, as Dr. Bonnet warns, many of the processes are worthless. Some destroy the strength of the fibre, some spoil the texture, some are only temporary. But, with expert technicians and laboratories at its command, the rayon industry may be expected some day to evolve a spun rayon which will have a practical and safe consumer use.
In the meantime, as consumers we are faced with the fact that a vast amount of spun rayon is already in use in the fabrics we buy. Although, in October 1937, the Federal Trade Commission made it mandatory for the rayon content of fabrics to be disclosed to the consumer buyer, the labeling is proceeding slowly and with some reluctance among certain sections of the garment industry. In self-protection the consumer who wants the greatest warmth must demand a guarantee of all-wool content in the fabrics he buys, and where less warmth is required it is necessary to ask for complete identification of all fibres present, since rayon requires particular handling and treatment in use.