22 momme, if the mask is a single unlined layer of charmeuse. 19 is enough the moment a lining or a filled cup sits behind the silk.
The general weight guidance for small silk goods puts eye masks at 19-22 momme. That range holds, but the usual reason behind it does not.
Nobody has published a light-transmission measurement for silk at any momme weight. The number on the listing cannot be a darkness rating, because darkness has never been measured against it.
Weight genuinely predicts how long a mask lasts under a nightly wash routine. What controls darkness instead is the weave’s tightness, the depth of the colour, the number of layers, and whether a lining or a filled cup backs the silk.
Higher momme adds more silk per unit area, but the variables that govern how much light a cloth passes are weave tightness, open area between threads, and depth of dye.
No published study has measured light transmission through silk at a stated momme weight. Textile optical testing, architectural shading research, and sleep-medicine lux work were all searched. None returns a silk-at-momme figure.
A 2021 experiment at the University of Ljubljana wove four fabrics from the same non-silk yarn at the same thread density and shows why weight alone falls short. Mass agreed to within 3%. Air permeability differed by 2 to 2.5 times.
Equal weight, completely unequal cloth.
Colour is the cheapest lever a shopper can pull. In a separate UV-protection study on cotton, depth of shade moved measured protection further than any weight step at the same construction.
A charcoal mask at 19 momme and an ivory one at 22 are not making the trade the listing suggests.
Charmeuse, the satin weave most silk masks use, blocks better than twill or plain at equal tightness in cotton UV tests because it packs threads more densely. The mechanism is weave geometry, and it transfers across fibres.
Let’s cut through the marketing claims: a listing that promises total blackout next to a momme number is citing a measurement that has never been made.
19 momme reaches the same darkness the moment a lining, a fill, or a moulded cup sits behind the silk, because a different layer is doing the light-blocking work.
The heaviest silk mask on sale confirms this. It runs 30 momme, not as a heavier flat panel but as the facing on a filled cup about three-quarters of an inch deep.
The same maker drops to 22 momme for the strap. The heaviest cloth on the market went into the part held away from the eye.
Padding keeps the silk off the eyelashes and adds darkness, but the residual leak is always at the nose bridge, lined or unlined. A simple readjustment fixes that gap better than a heavier panel does.
Past roughly 22 on a flat unlined panel, added weight arrives as warmth over the eye socket and bulk at the lash line before it arrives as darkness.
A custom-specified mask pairs the weight and the lining as a single decision at the factory, which is how a mask is actually built rather than chosen by one number on a listing.
Strap tension, nose-bridge seal, and lash-line contact decide whether a mask is actually worn all night. Strap tension is also a light variable no listing mentions.
Stretching any woven fabric opens its structure. In cotton UV tests, repeated extension dropped protection by 30 to 75%. A head strap applies far less force, but the direction is the same.
A mask cranked tight to stop it sliding is a mask whose panel has been pulled open.
Side sleepers face a harder version. Gravity presses the mask sideways against the pillow, and the nose-bridge gap opens regardless of how well the mask fits face-on.
The build that holds under side pressure is the moulded cup, which also traps more warmth around the eye socket than a flat panel does.
The same strap-and-fit challenge applies to sleep bonnets and nightcaps: any small silk piece worn on the head must stay seated without cranking the elastic.
Wearers with lash extensions are asking a different question: how far the cloth sits from the lash line, not which momme. A contoured cup with a padded bridge holds the silk off the lashes. A flat panel at any weight does not.
22 momme, because a mask worn on facial skin and skincare residue every night is washed at several times the cadence a pillowcase sees.
Weight is the one variable that genuinely predicts how the cloth holds up. Fabric mass and thickness raise abrasion resistance in any fibre, up to a density ceiling where threads jam together and can no longer deflect.
Laundering lowers the resistance carried into every night that follows.
Charmeuse sits at both ends of this trade-off. In pilling tests on cotton across five weaves and three laundering intervals, satin performed worst at every stage.
After five washes at 150 rubbing cycles, satin reached grade 1 of 5 while plain weave still held grade 4. The dense packing that makes charmeuse block well comes from long floats, and those floats are why it thins first.
The honest truth about silk is that the momme number on a listing measures durability, not darkness. A 22 momme mask outlasts a 19 momme mask in nightly wear, and that is the real reason to choose it.
For a flat unlined silk eye mask worn every night, 22 momme charmeuse is the weight to buy. It will not last as long as 22 momme in a pillowcase because a mask is washed more often, but it will outlast 19 under the same routine.
When a lining, a fill, or a contoured cup sits behind the silk, 19 momme is enough. The lighter cloth sits cooler against the face and lies flatter under a pillow, and the layer behind it is doing the blocking.
The weight ladder stops paying somewhere near 22. Past that point, added mass arrives as warmth and bulk before it arrives as darkness. The heaviest masks on the market are not heavier flat panels but moulded cups with a fill inside.
Check the listing for what sits behind the silk before choosing a number.