What is the natural fiber that darkens in color due to water based solutions?

Linen is known to be a natural fiber that can darken in color when exposed to water-based solutions. This phenomenon occurs due to the fiber's structure and its ability to absorb moisture. When linen comes into contact with water, it can swell and alter its light-reflecting properties, causing it to appear darker. This characteristic is particularly notable with darker dyes or during cleaning processes where water-based solvents may be used.

On the other hand, cotton, silk, and rayon have different properties and reactions to water. Cotton can also absorb moisture but typically does not exhibit the same degree of darkening as linen. Silk, while a natural fiber, is more sensitive to water and may suffer from damage or water spots rather than simply darkening. Rayon, which is a semi-synthetic fiber made from wood pulp, can absorb water and may change in appearance, but it does not do so in the same way as linen.

Understanding these properties is crucial for selecting the appropriate cleaning methods and for predicting how various fabrics will behave when exposed to different cleaning agents. This awareness also helps in maintaining the fabric's integrity and appearance.