I—A SIMPLE TECHNIQUE FOR INVESTIGATING THE EFFECT OF HUMIDITY ON THE FADING AND DEGRADATION OF DYED FABRICS BY SUNLIGHT, AND SOME OBSERVATIONS ON DYED COTTON

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Abstract
A simple technique is described whereby dyed fabrics may be exposed to daylight in air controlled at any desired relative humidity. The exposure units, which consist of modified fruit jars, have been used to study the effects of humidity on the fading and photochemical activities of a large number of different dyeings on cotton cloth. The increase in the fluidity of the dyed cloth during the exposure (ΔF) has been used as an empirical measure of the photochemical activity of the dye, and curves relating ΔF to the relative humidity have been constructed for several vat, and a few basic dyeings exposed at different relative humidities between 0 and 100 per cent r.h. For a given exposure, the rise in fluidity of the basic dyeings increases steadily with humidity, but the vat dyeings show no such relationship, most of them appearing less active at about 50 per cent than at 0 or 100 per cent r.h. The extent of fading of the vat dyeings, on the other hand, increases continuously with increasing humidity. Concurrent exposures of 46 vat dyeings at 10 per cent and 90 per cent r.h. show that the dyes differ very greatly in their response to humidity, both as regards fading and photochemical activity; these two properties are closely correlated at a given relative humidity. Similar experiments have been made with 38 azoic dyeings, several of which proved to be photochemically active at the higher humidity. As with the vat dyeings, the greatest activity was shown by dyeings that faded the most rapidly.

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