Here’s why.

While polyesters and synthetic fabrics don’t tend to shrink, natural fabrics like cotton and linen often shrink 3-5%.  Depending on the tightness of fabric weave, shrinkage can be as high as 10%. 

The greatest shrinkage for natural fabrics happens during the first wash and dry cycle. Lengthwise shrinkage is unrecoverable.  Crosswise shrinkage may ease with wear – such as your favourite pair of jeans just out of the dryer. 

By not pre-washing/shrinking your fabric before cutting/sewing, there is a very real risk of significant garment shrinkage.

Another important reason is to wash out the dirt / remove chemical sizing / starch treatments / excess dye from the production process. 

These processes make it easier for the manufacturers to handle the fabric during production. It strengthens the yarn for weaving and allows for the end fabric to look great on bolt! Washing your fabric softens the fabric. It also saves wear and tear on your tools. Scissors, cutting blades, needles can dull quickly. Excess dye/dirt debris on your sewing machine can lead to more maintenance.

It’s best to wash and dry the fabric like you’ll wash and dry the final garment. If you plan on hand washing or machine washing, pre-wash your fabric using that method. Dry either by air or in your dryer.  

When not to pre wash fabric?

100% synthetic fabrics do not need pre washing to prevent shrinkage, but it is still a good idea so you are working with a clean material.

For dry clean only textiles such as wool or knits, you can simply steam the fabric prior to cutting/sewing to help pre-shrink. Hover the iron above (not on! ) the fabric. 

The exception to the pre-wash rule on natural fabrics might be raw indigo denim. Creases and folds from washing the fabric may lead to white lines on your fabric.  You can open up the fabric, lay flat in bathtub, shake it out so it’s smooth. Air dry as a single sheet – not folded. 

Tips to Consider for Machine Pre-washing.

Unfold your fabric prior to putting it in the machine.

It’s best to wash the fabric on its own – not mixed in with other items.

Don’t overcrowd the washing machine and and don’t skimp on water.  Overcrowding and insufficient water, particularly with natural fabrics can lead to some areas of the fabric not getting full water coverage. You may end up with streaks in your fabric that usually are permanent.

The excess dye will wash out and could stain other items in the wash.

Shake out the fabric prior to placing in dryer or hanging to dry.  This ensures no permanent wrinkles or creases are created through the drying process.