What is momme silk, and why does it matter?

Momme is the unit silk gets weighed in. The luxury silk industry has spent twenty years selling at 19 momme while pretending the number doesn't matter. It matters.

If you're shopping for a silk pillowcase and you've never heard the word momme, the brands have done their job. Without the number, all silk feels like a vague luxury, soft, smooth, expensive enough to be premium. With the number, you can tell which is which. Here's what it measures, what it changes, and how to test it yourself.

The definition, simply

One momme equals 4.34 grams per square metre, or, more usefully, the weight in pounds of 100 yards of silk fabric that's 45 inches wide. The unit comes from Japan, where silk weighing dates back to the 8th century. Pronounce it "MOM-ee" or "moo-mee" depending on which textile veteran you ask.

For pillowcases and sleepwear, the practical range is 12 to 30 momme. Below 12 you're holding scarf material, too thin to take a wash. Above 30 you're holding upholstery weight, too heavy to drape over a pillow. The sweet spot for face-contact textiles sits between 19 and 25.

What the number actually changes

Higher momme silk has more Bombyx mori protein per square inch. That density does five specific things:

• Thicker drape. Higher momme silk hangs heavier. You notice this the first time you slip a new pillowcase over your pillow, the way it falls.
• Deeper color. Density absorbs more dye uniformly. A 22 momme charcoal looks deeper than a 19 momme charcoal in the same dyebath.
• Less translucency. Hold both up to light. The 19 lets through visibly more. The 22 reads as solid.
• More wash cycles before thinning. 19 momme pillowcases show wear at 80–100 washes. 22 momme survives 200+.
• Higher seam integrity. Threads in denser silk hold seam tension longer. Cheap silk seams pull apart at the corners; dense silk doesn't.

None of these differences scream from across a room. They show up over months. The 19 vs 22 difference is what separates a pillowcase you replace every two years from one you keep for six.

Why 19 became the standard

It's a margin play. Silk weaving is constrained by Bombyx mori spinning speed, silkworms produce filament at a fixed pace, and denser silk needs more of it per metre. Going from 19 momme to 22 increases material cost by roughly 18%. Going to 25 increases it by 35%.

Luxury brands settled on 19 in the early 2010s because it was the lowest weight that still felt unmistakably silk, past polyester satin but below the upmarket threshold where margins compress. Slip launched in 2013 at 19. Most peer brands matched within two years. The category froze there.

22 momme exists at brands that charge $130+ retail (Drowsy, Manito, a few smaller mills selling direct). At our $88 we're below that retail tier because we don't pay distribution markup, we sell direct, finish in our own workshop, and source from a single Italian mill rather than a global procurement chain.

Brand comparison, what each actually uses

If you're considering a brand not on this list and they don't disclose the momme weight, assume 19. We've never found a luxury silk pillowcase that hid its momme number and turned out to be at 22 or above. The brands above 19 want you to know.

How to test a pillowcase yourself

You probably can't measure momme at home without a precision scale and an exact 100-yard sample. What you can do is the relative test, compare two pillowcases side by side. Three quick checks:

• Hold them up to a window. Lower momme passes more light. Place both flat against a sunny window. The 22 reads opaque; the 19 reads slightly translucent at the same scale.
• Pinch and release. Roll a corner between thumb and forefinger. Higher momme bounces back faster and feels denser, like there's more material at the same surface area.
• Weigh on a kitchen scale. A Standard pillowcase at 22 momme weighs around 80 grams. A 19 momme Standard weighs around 65 grams. The 15-gram delta is consistent with the momme math.

The window test is the most reliable visual one. The weight test is the most reliable absolute one. If you're shopping in-store (some department stores stock luxury silk), do the pinch test on the display sample.

What we use and why

Casa Hush's Silk Pillowcase is 22 momme mulberry silk. We source from Setificio Mantellassi, a third-generation family mill in Como, Lombardy. Bombyx mori silkworms, no degumming shortcuts. Each Standard pillowcase weighs 80 grams (95 g for King). We disclose this on the product page, on the care card, and on the dust bag.

We went with 22 specifically because it's the practical maximum for daily-use pillowcases. 25 momme exists but trades a noticeable jump in cost for an only marginal increase in face-feel. 22 is where the curve flattens.

One more thing

Momme weight is only the headline number. Other things that matter alongside it: the silk's grade (6A mulberry is the highest), whether it's degummed properly (raw silk feels grippy and uncomfortable), the dye fixing process (cheap dyes wash out the first time), and the closure (envelope vs. zipper, zippers scratch faces). A 22 momme pillowcase from a sketchy mill is worse than a 19 momme pillowcase from a good one.

For more on what to look for, see our silk vs satin comparison and our care guide. For independent certification of textiles tested against the skin, see OEKO-TEX Standard 100, the global standard our materials hold.