Why does cotton shrink after washing? Cotton shrinks because it is a natural fibre that gets stretched during fabric manufacturing.Cotton does not stretch like elastic during manufacturing, but it is held under mechanical tension during spinning and weaving. When washed, this tension relaxes, causing shrinkage.When exposed to water and movement during washing, the fibres relax and return to their natural length, causing shrinkage. Does all cotton shrink the same way? No. Pure