Muslin is 100 percent cotton , and so many different grade available . There are bleached ( white) and Unbleached ( natural) . and there is a PFD ( prepared for dyeing). RonLov is one of the major manufactures of muslin , and has as many as 6 -8 muslin grades in both bleached and unbleached. Each of the grades has a code on the end of the bolt. If this is a fabric you think best , keep the code in your purse , so you can buy the same one each time.
This is the link so you can see the types that are manufactured by this company. Almost every store has RonLoc muslin in one type or another, the key is knowing which you are really getting.
This companies PFD muslin is number 408 called Natures Way .

http://www.roc-lon.com/products/muslins.html

Yes, muslin is cotton & can be dyed but if you buy just regular muslin, you have to prepare it for dying to get out the chemicals. They sell some called muslin pfd (prepared for dying).

Thank you both Lori S and BKrenning, this will solve my problem.

Ecology cloth is wonderful!!!!! I use it when doing scrappy quilts and have also used it for a background fabric. Great stuff

I prefer the perm. press muslin. I don't like the feel of the the cheap thin stiff muslin. The wide backing print muslin is nice. A good quality muslin will be about $3 - $4 a yard and never below $2, unless on a good sale.

This Quilting board is the best. Always a wealth of information! thank you

It is great used with 1930's prints in block designs.

Whatever you use it for, don't go cheap! Get a good quilt shop quality muslin. Stay away from Wal-Mart. I hear it falls apart after awhile.

Here is a very interesting article about muslin:

http://www.quiltersreview.com/articl...t/010820_b.asp

I use muslin if I'm changing the size of blocks in a quilt - make the blocks to be sure my math was right before I start in on the good fabric. I make some of my jackets and I'll make one with muslin first to be sure it fits correctly. Backing for table runners and a lot of wall hangings. Usually buy Kona or a good quality muslin. It's just handy to have around.