I only prewash when I feel the fabric may either bleed or shrink a lot, always prewash flannel, event the "best" quilters flannel will shrink, I do like the look of a quilt after it is washed which makes it look antique even when its brand new

100% cotton will shrink some, and not all fabric will shrink the same amount. Good enough reason to pre-wash?
I have found that I minimize the ironing needed by setting my washer for SLOW spin, then hanging fabric on the clothesline with pins every 10 - 12". Newer fabrics tend to wrinkle a lot less than older cottons. (I occasionally am given a piece I know is old by the 36" width -- they always wrinkle a lot more!)

No I don't prewash...I wait and wash when my quilt is finished. However, I always prewash flannel because of the shrinkage.

thanks

hands in air over this. if I wonder about color fast I will. found a new post here about a "bleeder" a fabric that will not stop from running.. so , wow.. would throw that out.. not worth the work to be hurt.
so, I do and I don't.. = no help !
but the reason I am posting is.. to warn you.. some fabric is just really safe, but not often found.

respect the nature of the fabric and wash or no wash accordingly. some shrink, some bleed and some do strange things....

If I am doing a planned quilt with only a few different fabrics, I prewash. For scrappy quilts I don't always do all the fabrics. When I wash my quilts I always throw a "color catcher" in the washer. So far has worked out okay. I'm probably due for a bleeding quilt!

i only prewash flannel.

i treat batiks with retayne.

if i had fabric from an unknown source (bought 2nd hand, gifted from some ones older stash) i would prewash it.

i feel very confident in the quality of the fabric i buy and dye and in 8 years have never had a single problem.