Today I made three bags.
First—the fabric. Muslin is cheap and utilitarian, but it gets dirty, it doesn't protect the piece from (god forbid) water or even worse, and it is a pain to stuff a rolled quilt into and out of a muslin bag—kind of like shoving your flannel-shirted arm into the sleeve of a fleece jacket. A couple years ago one of our members suggested we use a slick fabric of some kind, that the quilts could easily slide into and out of. Brilliant. I found a bolt of slick, waterproof nylon on the sale table at a fabric store and bought several yards, which will keep me in bags for the foreseeable future.
It's kind of an odd blue-gray color (probably why it was on sale), but very sturdy, nice stuff. I actually like the color and I can easily identify my packaged quilt in a crowd.
For the ones I made today I measured the rolled quilts and cut, for each, a rectangle that was wide enough to fit loosely around the rolled quilt, including a seam allowance, by the length + 8 inches. I hemmed one end, creating a channel I could run a cord through, then, before sewing up the side seam I stitched an acrylic photo pocket to the outside of the bag. Into this I will put a small photo of the quilt that will go inside. You can imagine how helpful that becomes to the people organizing and hanging the shows.
Then I sewed down the side and across the bottom. I always finish those inside seams by zigzagging the edges because, otherwise, that nylon really frays. A note about the photo pocket—some of the artists sew a ziplock bag on for the pocket and that works fine, but, in my opinion, gets a little ratty looking over time. I like the nice clear acrylic. I bought a pad of it at the art supply store.
To close the bag, some artists use Velcro, some a tie around the top. I like to run a nylon cord through the hemmed edge, then use one of those spring-loaded, pinchy fastener things like are used to tighten up the hood and bottom of your rain jacket. (Cheap at the fabric store or save them off discarded clothing) If you light a match, you can seal the cut ends of the nylon cord so it doesn't fray, then slip the ends through the fastener gizmo and tie a knot.
My quilts get to go to more places than I do. I like to see them travel in style.