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

Pre-washing fabrics before sewing is essential for several reasons, primarily because it helps shrink the fabric and remove any chemicals. Many fabrics can shrink after the first wash due to the relaxation of fibers that may have been stressed during the manufacturing process. By pre-washing, you ensure that any potential shrinkage occurs before the fabric is sewn into a finished garment. This is crucial to maintain the intended size and fit of the final product.

In addition to shrinkage, many textiles may also contain finishing agents or chemicals used during production that could affect the fabric's feel, appearance, or how it reacts when sewn. By washing the fabric beforehand, you can eliminate these chemicals, making the fabric safer and more pleasant to sew.

While there are other considerations when working with fabrics, such as accurately assessing color or testing for fraying, the primary and most significant reasons to pre-wash are to prevent shrinkage and remove potential chemical residues.