It is frequently stated that one fabric dries faster than another, usually with reference to house hold conditions of drying on a line. However, the data of this report show that by and large all fabrics dry at the same rate under these conditions (rate being expressed as weight of water evaporating per unit area per unit time), but that the time of drying depends upon the amount of water originally held, so that some fabrics dry sooner than others. The main portion of the drying time shows this constant rate of drying, although there is a final period which is short compared to the main drying period, during which the rate of drying decreases. The water-holding capacity of a fabric depends upon how the fabric is supported (vertically or horizontally) and upon the mechanical treatment given to remove water. For simple drainage in the vertical position, the water-holding capacity of small samples is more closely correlated with fabric thickness than with fabric weight. The kind of fiber—i.e., wool or cotton-and large differ ences in moisture affinity, as shown with Vinyon, also affect the water-holding capacity. How ever, these factors have almost no effect on rate of drying, since this is controlled by the resistance of air layers to the passage of heat. The thickness of these air layers is sufficient under ordinary conditions to smooth-over the fabric surface irregularities, even when these are rather large, as in rib knits or in cellular or waffle fabrics. Increasing the hairiness of the surface in order to give more area for evaporation is sometimes proposed as a means of increasing the drying rate, but results show that this is without effect except for extremely high, open naps, for which the effect is the opposite-the thickness of the layers of still air is increased and the drying retarded.

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The surface of a wool fiber consists of a series of overlapping scales so arranged that when the fiber is rubbed from the tip towards the root it is considerably rougher than when it is rubbed in the reverse direction. Accordingly, when a material containing wool fibers is sub mitted to mechanical action such as occurs in laundering or in fulling processes the fibers tend to migrate in the direction of their roots. This migration tendency is recognized as one of the principal factors in the formation of the entangled mass known as a felt, and in the excessive shrinkage which wool materials exhibit during laundering. An instrument for measuring these surface frictional properties on individual fibers is described. Measurements made on many wool fibers indicate large variations in frictional properties. The relationship between friction and diameter was studied and no significant correlation was found. Measurements made in the dry state resulted in all cases in lower values than measurements made on the same fibers in the wet state. The coefficients of friction of a few varieties of wool and of human hair and mohair are described.

A simple, rapid procedure for evaluating the feltability of wool in the form of top is pre sented. The method consists of subjecting a sliver to controlled wet mechanical action, and measuring its change in length. It yields results which correlate well with the shrinkage during laundering of garments made from the top; the method thus provides a useful tool for con trolling the application of some chemical shrink-resistant treatments in the mill. In addition, this method shows promise of usefulness as a tool for investigating the nature of felting.

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