Fiber contamination is a serous and expensive problem for the mills. This includes stickiness from insect sugars, grass and bark and synthetic fibers.
Stickiness is caused by insect sugars on the fiber forming sticky deposits on the surfaces of mill machinery with which cotton comes into contact. The same deposits are often seen in gins (especially roller gins) and they can make ginning very difficult, the same way they make carding, drawing and spinning difficult for mills. Ginners can use a textile over-spray (containing a textile lubricant) to make the gin run smoother but the effect of the lubricant does not carry over into the mill. Increasing dryer temperatures to drive out any moisture is the easiest method to process sticky cotton. Control of late season insects is the only way to prevent the deposits of various tacky sugar compounds on the fiber.
Grass and bark enters the system during the harvesting and field storage process. Once this material gets ground up, it can resemble fibers and is difficult to separate from the cotton. The keys are to keep it from getting in to the seed-cotton or remove it before ginning. Classers look for grass and bark while grading the cotton and it is discounted based on the level of material in the sample. When grass and bark are problems, ginners must provide good pre-cleaning of seed cotton before ginning.
Foreign fibers or other contaminates can enter into the cotton during harvesting, field storage and ginning. Module covers and tie downs have been major source of fiber contamination. Once this material gets into the gin or the mill, it is distributed through out the fibers and is difficult to remove. It is very difficult to detect until the fabric has been dyed. Ginners must be aware of the problems with contamination of cotton and instruct workers of the same.