Most fabrics shrink in the dryer, not from being washed. You could sew a block together, sew around the outside perimeter and measure it. Put it in a lingerie bag and dry it. Look and see if it shrinks all over or if the cottons are distorting it.

I would say use it only if you can't find any other cotton you like.

The only thing I know is that the poly is much thinner than the cotton. Also it may ravel a bit.

A while ago ... well, several years ago when I started quilting, I ran short of white cotton to finish a wall hanging and finished it up with a white poly/cotton I had on hand. Over the years, the p/c has turned a nasty shade of tan and it is right next to the 100% cotton. Every time I see it, I say to my self ... see, that's why we use 100% cotton! I don't know how black p/c will age but the choice is up to you. If your quilt will not be exposed to a lot of sun light, the chances of fading won't be as great. LOL

:hunf: i agree. along with hottest water, the drier is the culprit!!

Oh my goodness, with all the work and time involved in making a quilt I would buy the best fabric you can afford. You will not be sorry and you might be if you use something that is "iffy." I always use 100% cotton only in my quilts.

Before you attempt to finish the quilt with questionalble fabric, go to Keepsake Quiliting. They have high quality black fabric that is 100% cotton. I've used it in several quilts & have never been disappointed. Good luck!

there are reasons i prefer to work with 100% cotton. quality is NOT one of those reasons. polyester is not inferior to cotton. it is merely different.

you have two potential issues to consider: (1) fraying; (2) shrinking

any fabric of any content can fray. that is your only real worry. use your rotary cutter to trim a straight edge at one end of the poly/cotton blend. sew a 1/4" seam along that edge and then toss it into the washer. check to see whether or how much that end frayed in the wash. turn the seam right-side out and tug on it a bit to see if it comes apart. if the seam holds then worry 1 is worry none.

as to the shrink issue ... do you plan to always hang the quilt to dry? if you do, then use the fabrics you have.

if you were planning to chuck it into the dryer, just change that plan.