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Description: COTTON DUCK CLOTH (INDIAN) - Investigation into the causes of discoloration of a shipment of Indian duck cloth revealed that the discoloration was not due to mold growth. Exposure to ultra violet light did not reveal the presence of mineral oils Qualitative tests indicated that the yellowish discolorations observed were due to natural oils and waxes which had not been removed in that part of the bleaching process of the cotton fabric known as the lye treatment. Quantitative tests revealed that the ether-soluble materials contained in the fabric amounted to over 1%. This suggests that a small amount of other naturally occurring matter, apart from waxes, extracted in the ether, since the maximum content of oils and waxes in cotton is approximately 1%. After ether extraction, a few yellow spots still remained on the fabric. These were probably calcium and/or magnesium soaps. When cotton fabric has undergone efficient lye treatment the ether extract from the material should not exceed 0.01%. The lye boiling is the most important operation in the bleaching process. Briefly it consists of boiling the goods with a dilute solution of alkali in order to remove such impurities as oils, waxes, mineral oils, proteins, etc. Owing to incomplete lye boiling, yellowish discolorations occur because of unremoved oils and waxes. Unremoved wax may not be apparent directly after the bleaching process, but when the goods are stored; it works its way to the surface, giving the goods a yellow tint. The light gray and yellow discoloration observed in the cloth under test was possibly due to incomplete bleaching of the fabric owing to the presence of unremoved waxes. A treatment somewhat similar to that carried out in the lye boiling was performed on the sample in the laboratory. An extremely high loss in weight occurred. Although a loss was due to naturally occurring impurities, the greater part of the loss was probably due to substances used in the bleaching process and unremoved from the duck. From the above findings the analyst was of the opinion that the discoloration was primarily due to incomplete removal of oils and waxes in the lye boiling. See also FABRICS. See also IMDG Code & US CFR.
Index: 816

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