Why is it important to pre-wash fabric before sewing?

Pre-washing fabric before sewing is essential primarily to prevent shrinkage and remove any residual chemicals or dyes. Many fabrics are treated with chemicals during production, including sizing agents that can affect the way a fabric handles and drapes. Washing the fabric beforehand ensures that these substances are removed and that any potential shrinkage is taken care of, preventing unpleasant surprises after the garment is completed. If fabric shrinks after construction, it can lead to a garment that does not fit properly or becomes unusable.

Additionally, many fabrics will shrink slightly when washed for the first time, so pre-washing helps to maintain the intended dimensions of the finished project. This step is critical for achieving accurate measurements and ensuring the longevity of the sewing project, giving you confidence that the final product will maintain the desired shape and size after being laundered.