A fabric, white or ivory, made of finely woven cotton. It can be painted or dyed to produce a backdrop or treated to be made semi-translucent. Muslin shrinks when it is painted. Muslin comes in a great variety of sizes. Fabric stores typically sell it in widths of 36" to about 102". Theatrical suppliers sell it in widths up to 39 feet! Muslin is very flammable. If you are using muslin purchased from a fabric store you should treat it with flame retardant before using it on stage. Theatrical suppliers can sell you muslin that is pretreated with flame retardant for only a dollar or two more per yard.