You've seen the label say "100% silk," but the pillowcase in your hands feels thin, clingy, and a little too shiny. Or maybe you're shopping online and the photos look identical to the real thing, but the price seems too good to be true. Telling genuine mulberry silk apart from satin (which is a weave, not a fiber, and is usually polyester or nylon underneath) doesn't require a lab. A handful of simple checks, done in under a minute, will tell you almost everything you need to know.
In this guide:
The Feel and Temperature Test
Pick the fabric up and press it against the inside of your wrist for a few seconds. Real mulberry silk is a protein fiber, and protein fibers conduct heat differently than synthetic ones. Genuine silk feels cool to the touch at first, then warms quickly to match your skin. Polyester satin, by contrast, tends to feel either slightly plasticky from the first touch or oddly slippery in a way that doesn't change much with your body heat.
There's a second part to this test: friction. Rub the fabric gently between your thumb and forefinger. Mulberry silk has a very faint, almost imperceptible roughness; it's smooth, but not glassy-smooth. Satin woven from synthetic fiber usually feels frictionless and slick, almost like it's coated in something. If you own one of our Silk Pillowcases already, this is a good moment to feel the genuine article and recalibrate what "real silk" actually feels like before testing anything else.
The Sheen Test
Hold the fabric up and tilt it under a light source, rotating it slowly. Mulberry silk fiber has a naturally triangular cross-section, which is why it refracts light at multiple angles and produces a soft, almost pearly sheen that shifts as you move it. It's lustrous without being blinding.
Polyester or nylon satin is engineered to look shiny from every angle at once. The result is a flatter, more uniform shine that often looks closer to plastic or glass than to fabric. If the sheen doesn't change much as you tilt the material, that's a signal you're looking at a synthetic weave rather than a natural fiber.
Pro Tip: Combine the sheen test with the feel test and you can usually form a reliable opinion in under ten seconds, even standing at a store shelf. If both point the same direction (soft shifting sheen plus a faint, warm-to-cool touch), you're very likely looking at genuine silk.
The Scrunch Test
Gather a section of the fabric in your fist and squeeze it tightly for about five seconds, then let go. Real mulberry silk creases, but the creases are soft and tend to fall out or soften again within a minute or two as the fiber relaxes. Press it gently and the wrinkles ease.
Synthetic satin behaves differently in one of two ways: either it barely wrinkles at all (a sign of certain coated polyesters), or it wrinkles sharply and holds those creases stubbornly, almost like paper. Neither of those is how a natural protein fiber behaves. This is also a useful test for anything woven from mulberry silk, not just pillowcases - it works the same way on a silk bonnet or a scrunchie.
The Burn Test
A safety note first: only do this on a small, already-loose thread snipped from a hem or an off-cut, never on fabric you plan to keep intact, and do it over a sink or a non-flammable surface, away from anything else that could catch. If you're not comfortable handling an open flame, skip this test and rely on the others.
Silk is a protein fiber, the same broad family as wool and hair. When a strand is touched briefly to a flame, it doesn't melt or shrink away from the heat the way plastic does. It singes, curls, and self-extinguishes almost as soon as you take the flame away, leaving behind a crumbly, dark ash that breaks apart easily between your fingers. The smell is distinctive too: burning hair or feathers, not melting plastic.
Polyester and nylon, being man-made from petroleum-based plastics, behave in exactly the way you'd expect from plastic: the thread melts, shrinks away from the flame, often beads up at the tip, and keeps burning with a sooty, chemical smell instead of self-extinguishing. If you test a thread from a bonnet or a pillowcase side-seam and see melting instead of ash, that's a conclusive result; this test rarely leaves room for doubt.
Reading the Label (and the Momme)
Before you even touch the fabric, the label and listing tell you a lot. "100% mulberry silk" is a fiber claim. "Silk-like," "satin," "silky," or "silk touch" are weave or texture claims, and they say nothing about the actual fiber inside - that fabric is very often 100% polyester. Read the fiber content line specifically, not just the product name.
Next, check whether a momme weight is stated at all. Momme (abbreviated "mm" and pronounced "mo-mi") measures the weight and density of silk per unit of area, similar to how thread count is used for cotton. A listing with no momme figure anywhere is a small red flag on its own - it usually means there's nothing favorable to report. At SilkWide we weave our pillowcases, bonnets, sleep masks, scrunchies, and hair curler from 23 Momme mulberry silk charmeuse, and we state that figure on every product page because it's a meaningful, checkable number, not a marketing word. You can read more about what the number actually means and why it matters in 7 Facts About Mulberry Silk You Need to Know.
One honest caveat: a stated momme number is not, by itself, proof of authenticity - a dishonest seller could print any number they like. Use it alongside the other tests here, not instead of them.
The Price Sanity Check
Mulberry silk is a genuinely expensive material to produce: it takes a large number of silkworm cocoons, a slow unwinding process, and skilled weaving to make a single pillowcase. A queen-size silk pillowcase that's priced like a basic cotton one is almost never real 100% mulberry silk at a meaningful momme weight - the economics simply don't work.
As a reference point, our own Silk Pillowcases, woven from 23 Momme mulberry silk charmeuse, are priced at €56.95-€59.95 depending on size and colour. That's a realistic range for genuine mulberry silk at that weight from a direct-to-consumer brand. If you see a "100% silk" pillowcase advertised for a fraction of that with no momme figure stated anywhere, treat the claim with real skepticism and run it through the other five tests before buying.
If you're ready to build out a full silk sleep routine rather than testing a single piece, our Silk Bedding collection covers sheets and duvet covers made from the same quality standard.
Can polyester satin ever pass the burn test for silk?
No. This is the most reliable test of the six precisely because the underlying chemistry can't be faked. Polyester and nylon are plastics, and plastics melt and shrink from heat; silk is a protein fiber that singes to a crumbly ash. There's no way to make a synthetic thread behave like a protein fiber under a flame.
Does "100% silk" on the label guarantee it's mulberry silk?
It guarantees the fiber is silk, but not which type. There are other types of silk (tussah or "wild" silk, for example) that are genuinely silk but coarser, less lustrous, and usually cheaper than mulberry silk. "100% silk" is honest about the fiber family; "100% mulberry silk" is the more specific and more useful claim to look for.
Is an OEKO-TEX certification proof that a product is real silk?
Not on its own. OEKO-TEX Standard 100 (which is the certification SilkWide holds) tests a finished textile for harmful substances and chemical safety - it's a safety certification, not a fiber-identity certification. A polyester satin pillowcase could, in theory, carry the same safety certification. Use it as a sign a brand takes manufacturing safety seriously, not as fiber-authenticity proof.
What momme weight should a real silk pillowcase be?
There's no single legal minimum, but anything under roughly 16-19 momme tends to feel thin and see-through, and won't hold up well to regular washing. Most reputable mulberry silk pillowcases sit between 19 and 25 momme; SilkWide's are 23 momme. Momme is a density measurement, not a brand name, so it's worth comparing across brands directly.
Can I safely test a silk item I already own without damaging it?
The feel, sheen, and scrunch tests are completely safe and leave no mark. The burn test should only ever be done on a loose thread you're willing to lose, snipped from an inside seam or hem, never on the main fabric - treat it as a last resort for when the first three tests leave you unsure.
