Water and Mold Damage - Cotton, particularly in the raw state, mildews rapidly under damp conditions without necessarily being the subject of any fortuity such as wetting by fresh water, seawater, etc. The infection causing mildew, and possibly subsequent decay, may take place from the cotton field onwards, and it only requires conditions of sufficient moisture for this to develop. The formation of mildew is also favored by warm as well as moist conditions. Such damage, in cotton fibers, may result from the process of wetting before shipment. The chief result of damage by mold is the lowering of the grade because of stains and discoloration, but a chemical action is set up which causes decay in course of time. Heating will also result in decay.
Water, wither rain water, seawater or sweat, penetrates slowly owing to the density of the bale and causes staining and rotting of the fiber. Such damaged fiber, however, is not worthless, but can be used when mixed in small quantities with undamaged fiber during spinning. Water damaged cotton is not subject to spontaneous combustion, but contact with oil can be dangerous. The oil is absorbed and in the close confines of the vessels' hold the subsequent evaporation might easily produce an explosive mixture of air and oil vapor with a low flash point. The actual wetting of cotton fiber has no harmful effect, but unless dealt with promptly the initial wetting may result in mold, damage by staining, or, if treatment is unduly delayed, will cause decay.
The extent and rapidity with which deterioration of the cotton occurs varies according to the grade and density of the cotton and according to the conditions and extent of the wetting. The wetting of cotton will set up heat some days after the wetting has occurred or, if the bales are submerged, some days after being taken from the water. At temperatures below freezing there is little or no danger of decay, as the process is arrested at low temperatures. In some cases where delay in dealing with the cotton could not be avoided it has been put into cold storage to prevent the development of decay.
If bales have been thoroughly wetted, the cutting of the bands to release the pressure should be considered, as heating will increase in compressed cotton whereas the opening of the bales will arrest the process of deterioration.
Where wetting has not penetrated very deeply into the bales they can be left in the open under drying conditions, which should be sufficient to restore them, but if they are thoroughly wetted then the bales should be opened up and dried as soon as possible. Artificial drying may sometimes be detrimental to the final appearance of the cotton as it may become spotted or yellow stained. The natural process of drying, if available, is to be preferred, the main question in the case of wet-damaged cotton being to deal with it as promptly as possible.
Cotton consists of the unicellular seed-hairs of the bolls of the cotton plant (Gossypium hirsutum), which belong to the "plant hair" category. The cotton plant itself belongs to the mallow (Malvaceae) family. The fruits of the cotton plant burst when ripe, revealing a fist-sized tuft of cotton consisting of fibers up to 50 mm in length. Once picked, the cotton is dried in the sun and ginned (separation of seeds from fibers).
The plant fibers have a pronounced three-walled structure. The outer wax layer protects the primary wall. The most important element is the secondary wall, which consists predominantly of cellulose. The tertiary wall surrounds the lumen, which, in all cellulose materials of plant origin, is very well formed and filled with air.
The chemical composition of cotton is as follows:
- cellulose 91.00%
- water 7.85%
- protoplasm, pectins 0.55%
- waxes, fatty substances 0.40%
- mineral salts 0.20%
- Commodity Name:
COTTON AND COTTON GOODS