Of course there’s a never-ending debate regarding whether to prewash fabric and I’ve been back and forth several times over the years. I usually resume prewashing when something fades and runs in a finished quilt, but I mostly don’t prewash. My theory is that most (not all!) modern fabrics are colorfast. Of course cotton fabric shrinks, but most people expect quilts to be crinkly due to cotton batting, so it doesn’t really matter if the fabric shrinks, too.

Here’s a quilt in which cotton batting produced even crinkles
Enter my class with Tara Faughnan, which I’ve found very useful. Tara advised prewashing because different colors of fabric shrink different amounts! She also noted that prewashing then starching makes the different weaves on the market (think Kona solids vs Cotton Couture solids) behave similarly when you get around to sewing them.
I just said ho-hum and went on my way. Then this happened:

Yikes!
Well! Those are 2″ squares, so the amount of shrinking in that middle one is kind of alarming. Furthermore, it appears that warp and weft shrink differently, which is not actually a surprise. The cause of the shrinkage in this case was just ironing with water spray.
So I got out all my solids to pre-wash. I washed in color-coordinated loads, with color catchers. There was a little bit of fading with the reds, but otherwise nothing faded. I didn’t try to evaluate shrinkage.
So I’m back in the pre-wash camp. Where are you this week?