When is cellulosic browning most likely to occur?

Cellulosic browning is a common issue that arises primarily when carpets made of natural fibers such as rayon or other cellulosic materials are subjected to excessive moisture. When a carpet is over-wet, it can create conditions that lead to the breakdown of cellulose fibers, which results in a brown discoloration on the surface of the carpet. This phenomenon is often exacerbated in situations where moisture remains trapped, fostering an environment conducive to browning.

In contrast, dry cleaning methods are designed to minimize the moisture level, thereby reducing the likelihood of browning. Similarly, the use of acidic cleaners is typically aimed at neutralizing alkalinity, which can actually help in preventing discoloration rather than causing it. Lastly, while hot water extraction involves significant moisture, the potential for browning occurs mainly when carpets are not dried adequately after such cleaning. Therefore, the scenario that poses the highest risk for cellulosic browning is indeed when a carpet is over-wet, as this directly influences the condition of the fibers.