Alkaline residues and over wetting could result in what in rayon fibers?

Browning occurs in rayon fibers as a result of alkaline residues and over-wetting. Rayon is a semi-synthetic fiber made from cellulose, and it is particularly sensitive to alkaline conditions and excessive moisture.

When alkaline cleaners are used or if the fabric is subjected to overly wet conditions, the rayon fibers can undergo a chemical reaction that leads to a discoloration known as browning. This discoloration is often the result of the fiber reacting with moisture and alkali, which can cause degradation of the dyes used in the fabric. In addition, over-wetting can also cause the fibers to swell and absorb more color, which can enhance the browning effect.

In contrast, other options like fading, stretching, and cracking do not directly result from alkaline residues or over-wetting in the same way that browning does. Fading might occur due to prolonged exposure to light rather than the specific chemical reactions involved with alkaline and moisture. Stretching pertains more to physical damage due to mechanical forces rather than chemical reactions. Cracking could occur in some materials when they dry out after being saturated with water but is not a typical consequence of alkaline residues or over-wetting in rayon fibers. Thus, the best answer is browning as it directly addresses the effects of alkaline