A washing machine is designed to clean clothes efficiently, but the process can sometimes cause unintended damage such as shrinking, fading, or pilling, according to textile experts. Understanding how washing machines work and how different fabrics react to the process sheds light on why such issues occur.

Professor Muhammad Abdur Rahman Bhuiyan, from the Department of Textile Engineering at Dhaka University of Engineering & Technology, explains that effective washing relies on two key factors: detergent and mechanical movement. Detergents contain surfactants, molecules that attach to both water and oils, allowing greasy stains to be lifted from fabric fibers and dispersed in the wash water. Meanwhile, controlled movement inside the machine agitates the clothes to loosen dirt.

Modern washing machines typically allow water in through an inlet valve, mix in detergent, then move the clothes either by a rotating drum in front-loaders or an agitator in some top-loaders. Once washing is complete, soiled water is drained, clothes are rinsed to remove remaining dirt and detergent, and a high-speed spin extracts excess moisture.

While this process is effective at cleaning, the mechanical forces at play can also cause wear. Friction between clothes and the drum or other garments can loosen fibers, leading to pilling, weakening, and changes in appearance over time. Different fabrics respond differently; cotton and denim generally withstand regular washing better, though dyed cotton may fade and shrink. Polyester can retain odors despite washing and requires careful handling.

Wool is especially vulnerable due to the structure of its fibers, which have microscopic scales. When subjected to vigorous rubbing in water, these scales can interlock, causing the fabric to felt and shrink — a phenomenon likely responsible for some consumers’ experiences of their wool garments shrinking unexpectedly. This process is distinct from mere shrinking caused by heat.

Studies have shown that gentler washing methods can reduce felting. For instance, research comparing ultrasonic waves to hand washing revealed less fiber displacement and better stain removal with ultrasonic cleaning, though typical home machines were not tested. Nonetheless, these findings highlight the importance of how fabric movement is managed during washing.

To accommodate different fabrics, many washing machines now feature specialized cycles for cotton, synthetics, wool, and delicates, adjusting parameters like water temperature, drum speed, agitation intensity, washing duration, and spin speeds. Users are advised to follow care labels carefully, as some wool and silk items are treated to resist shrinkage and can be machine washed safely, whereas others require gentler handling.

Proper loading and detergent use are also crucial. Overcrowding the machine can prevent adequate water and detergent circulation, reducing cleaning effectiveness, while using excessive detergent can leave residues if not rinsed properly. The goal is to clean clothes thoroughly while preserving their fabric integrity.

Consumer experiences such as those of Lipi Akter from Dhaka, whose wool sweater shrank after machine washing, underscore the need for careful consideration of washing practices. While a washing machine’s primary function is to remove dirt, how it does so can significantly affect the longevity and appearance of garments.