Most quilters are firmly in one camp or the other when it comes to prewashing quilting fabric. Sometimes because they believe strongly in the reasons for their side. And sometimes because that’s what they were taught and it’s become a confirmed habit. There are advantages to each practice.
Washing your fabric will let you know ahead of time if a color is going to run. It’s so upsetting to put hours and hours into finishing a quilt and then have a color bleed and ruin your work. Tossing a color catcher in the wash water with your fabric or your quilt can prevent a disaster…. it’s a small price to pay.
The wash water (and it can be just plain water, you don’t really need to add soap) will wash out the chemicals added when the fabric was produced. If you are sensitive to this kind of thing, washing first is a good idea. Both the washer and the dryer will cause the cotton fabric to relax and to shrink a bit. Your finished quilt will be more true to size if you have pre-washed.
Now, if you don’t prewash, you get to play with your fabric right away! Washing will usually require that you press the fabric…. no washing = no pressing (unless it was really wrinkled on the bolt). The fabric will also be a little stiffer because of the chemicals and because the fibers are still stretched from the manufacturing process. This means it will be easier to rotary cut.
And when you finish your quilt made from unwashed fabrics and run it through the washer and dryer it will come out all crinkly and puckery…. a ready made vintage look!
So which camp are you in? Do you prewash? Or do you just jump right in? Do you have any other reasons for which rule you prefer to follow?