From Cookipedia(Redirected from Butter muslin)
Cheesecloth is a loose-woven cotton gauze used in cheese making, such as to press cheese curds. Cheesecloth is also used in straining stocks and custards, bundling herbs, making tofu, and thickening yogurt. Muslin or other lightweight fine-weave cloths are good substitutes for a cheesecloth.
Cheesecloth is available in at least seven different grades, from open to extra-fine weave. Grades are distinguished by the number of threads per inch in each direction.
Wash cheese cloth in cold water first as hot water will 'cook' the cheese onto the cloth. It's worth boiling a cheesecloth in plain water if it has been washed in detergent as it may taint the cheese otherwise.
A cheesecloth has a similar function to a jelly-bag.