The easiest test is to hold the fabric up to a window. Real muslin has an open, loose weave, so you'll see small, even gaps between the threads where light comes through. Run your hand across it too: the surface should feel soft and a little textured, not slick or shiny. A lot of fabric sold as muslin is actually a tightly woven synthetic blend, and checking whether a fabric is genuine muslin cotton or a synthetic look-alike is a good next step if the weave test alone doesn't settle it.
Wash is where the difference really shows. Real muslin cotton creases easily, and that's normal, not a flaw. It also gets noticeably softer after every wash, since the loose, open weave lets water and air move through more freely. That same openness is why muslin breathes better than a tighter weave like regular cotton. Synthetic imitations tend to stay stiff and resist wrinkling, no matter how many times you wash them.
Epic's clothes are double-layer muslin cotton. They're pre-washed so they arrive soft instead of stiff off the shelf, and sewn with flat seams, finished with child-safe dyes and no harsh finishes. If you want to see how muslin stacks up against the fabric already in your drawers, a side-by-side comparison of muslin cotton and regular cotton for babies covers the differences in weight and breathability. Wash cold on a gentle cycle, then tumble dry low or hang to dry. Skip the fabric softener and high heat: both flatten the weave over time. Sizes run roughly newborn to 4 years. Epic is a small family business run by Vanessa and Bob, who design in Bali, and it ships worldwide with tracked delivery and takes unworn returns within 30 days.