Ditto from my sewing room. Never a problem.

I've used JoAnn's premium muslin for both the backing and for pieced blocks and have never had any problems.

I have used Joann's premium muslin for several backs recently and do not prewash my backs. I find that if I do prewash the back, it slips a little more and I get puckers on the back. I pin-baste (hate the spray glue) on a bed or large table and I quilt on my Elna Excellence 720. If you do prewash, I recommend you starch the backing well.

I made curtains from it .I found that it shrank at least 1.5 inches per yard in length when I washed it.

I prewash everything.

I used it once for a backing of a top I made from 1930s (or reproduction) fabrics that my kids bought at an estate sale; it seemed fitting. As I remember -- it's been a few years....and that quilt is still not quilted! -- I pre-washed because someone warned me about shrinkage.

Please think about a pretty back. To me, muslin is a cop out. Your top is probably beautiful and required lots of time and talent. Put pretty on the back as well. Just my opinion.

For muslin, I would prewash it. I don’t think it will matter if the top fabrics has been prewashed or not. The muslin will probably shrink a little bit more.

I don’t think muslin is a cop out. It is a matter of choice. I like to use it on the back of my vintage quilt tops. It is more with the time period than something “pretty”. It also showcases the quilting (if that is what is desired).

I would have to disagree with Suz as well. A muslin back is not a cop out. In addition to the reasons Ellen 1 has mentioned another big factor is cost. I would say maybe the biggest factor. Depending on the size of the quilt buying up to 8 yards of premium LQS fabric at $10-$13 a yard is a lot of money.