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It may sound weird, but that’s because fabrics are already shrunken by nature. In fact, the big change takes place during the manufacturing process, when clothes go through machines that stretch their fibers, which are naturally shrunk. This means that all the clothing in the stores has its threads stressed and under tension. “But over time they tend to relax, recovering their original shape”, says engineer Paulo Alfieri, from the Faculty of Industrial Engineering (FEI), in São Bernardo do Campo (SP). With the beating of the machine or the tank, the fibers relax quickly. To avoid this undesirable effect, factories bet on pre-shrunk clothes, when the fabric goes to the store washed or compressed by special machines. These processes don’t work 100%, but they at least ensure that the fabric doesn’t shrink as much when it reaches the wardrobe.
However, the only way to eliminate the problem for good is to use synthetic fibers, such as nylon or polyester, which are much more stable and have more malleability. The downside is that synthetic fibers are not as soft as natural fabrics. To reduce discomfort, many manufacturers mix natural and synthetic fibers in the same garment. This is the case of Lycra-type clothes, which fuse cotton with elastane. “Imagine that a blouse made from these two fabrics has shrunk, say, 5% in width. If the elastane allows the garment to stretch by around 35%, it normally returns to the size it was before,” says Paulo.
In the first wash, the artificially stretched fibers come together
natural reduction
Clothes made with cotton, for example, leave the factory with the fibers stretched. In this situation, its molecules slide over each other, pulling the entire structure. After being washed, the fibers tend to return to their natural state, with the molecules closer together. The result is that the clothes end up shrinking. The same thing happens with all other natural fabrics, such as linen and wool, and some artificial ones, such as viscose and rayon.
synthetic immunity
Synthetic fabrics such as nylon or polyester are virtually non-shrinking. The secret is that these fabrics basically behave like plastics: their fibers are constructed from petroleum derivatives and can easily be molded in the factory. More malleable and stable, clothes made from synthetic fabrics arrive at the wardrobe with a fixed size. Their shrinkage is negligible, but they are much less soft than natural fabrics.