The complete guide
The Buyer's Guide to 25 Momme White Silk Pillowcases
The problem with the pillowcase you already own
Most people never think about their pillowcase. It came with the sheet set, it is cotton or a cotton blend, and it does the job of covering a pillow. Then one morning you notice your hair is a mess in a way it was not the night before, or you see the sheet creases pressed into your cheek while you brush your teeth.
That is friction. A woven cotton pillowcase has a textured surface. Your face and hair press into it for seven or eight hours and drag across it every time you turn. The fabric grips. Silk does not grip in the same way, because the filaments are long, smooth and tightly woven. Hair slides across the surface instead of catching on it.
That is the whole pitch, really. No magic, no miracle. Just a smoother surface against your head for a third of your life.
What momme actually tells you
If you have shopped for silk at all, you have run into the word momme and probably skipped past it. It is worth two minutes of attention, because it is the single most useful number on a silk listing.
Momme (pronounced "mommy") is a traditional Japanese weight measure. For pillowcases it tells you how heavy the silk is per unit of area. Lower numbers mean a lighter, thinner cloth. Higher numbers mean a denser weave with more silk in it.
The market mostly sits between 16 and 25 momme. Below 16 the fabric gets thin enough that it starts to feel flimsy and wears out quickly at the seams. Around 19 momme is the common mid-range, and it is perfectly decent. At 25 momme you are at the heavier end of what is normally sold for bedding.
These cases are 25 momme. In practice that means the cloth has a bit of body to it. It settles over the pillow rather than clinging to every lump. It survives washing better, because there is simply more fibre there to take the wear. If you are comparing a best pure silk pillowcase against a cheaper one and the specs look similar otherwise, momme is usually where the difference hides.
The listing also quotes a 600 thread count. With silk, thread count is less meaningful than it is with cotton, because silk filaments are much finer and the numbers are not directly comparable. Treat momme as the headline figure and thread count as a footnote.
Silk on both sides, and why that matters
Here is a trick that shows up constantly in the budget end of the market. A case is advertised as silk, and it is, but only on one face. The other side is a cheaper fibre, often polyester or a satin blend. It keeps the price down and it looks fine in a photo.
The problem shows up at 2am. You flip the pillow over for a cool side, and suddenly you are lying on a different fabric entirely. Or you make the bed and the silk side is facing the mattress.
These cases are 100% mulberry silk on both faces. Either side up, same feel. It sounds like a small thing and it is a small thing, but it removes a small daily annoyance, and small daily annoyances are most of what good bedding solves.
Mulberry silk specifically means the silkworms were fed on mulberry leaves under controlled conditions, which produces long, even, uniform filaments. Wild silks have shorter, more irregular fibres and a slubbier texture. For a smooth pillowcase, mulberry is the fibre you want.
Getting the size right
This is where most returns come from, so take the extra minute.
These are cut to the American standard size, 20 x 26 inches (51 x 66 cm). In American sizing the three common cuts are standard at 20 x 26, queen at 20 x 30 and king at 20 x 36. The width stays the same across all three. Only the length changes.
Pillow sizes vary by region, and plenty of pillows sold outside the United States do not match any of those three cuts exactly. So do not assume. Take a tape measure, lay your pillow flat, and measure the long edge. If it comes in at or under 26 inches, standard is your size. If it is closer to 30, you want queen. If it is 34 or more, you need king.
A case that is slightly generous is fine. A case that is too short is not, because you will be wrestling the pillow in and the silk will be under tension at the seams every night.
The zipper question
These close with an invisible zipper set into the seam at one end. There are two schools of thought on pillowcase closures and both are reasonable.
A zip holds the pillow firmly. It does not creep out, it does not bunch, and the end of the pillow stays square when the bed is made. It is also easy to get the pillow in and out. The downside is that a zip is hardware, and hardware is one more thing that can fail on a well-used case.
An envelope flap has no hardware at all. It is a fold of fabric that tucks the pillow end in. It is simple and it lasts, but pillows do work loose over time, especially if you move around a lot.
If a secure fit matters more to you than absolute simplicity, the zip is the better option. Just close it before washing so the teeth cannot catch the fabric in the water.
Living with white
Solid white is the easiest colour in bedding, which is why hotels never deviate from it. It goes with everything. Charcoal sheets, navy duvet, floral quilt, bare linen, it all works. You never have to think about whether the pillowcases match.
White does ask for a little care. Any white fabric can shift tone over years if it is washed harshly or dried in strong sun. Skip the bleach, use a mild detergent made for delicates, and dry in the shade rather than on a sunny balcony. That is most of it.
Care, honestly
The stated care here is hand wash only. Not machine wash on delicate, not a laundry bag on cold. Hand wash.
For some people that is a dealbreaker, and it is fair to decide that now rather than after you have bought. For everyone else, it is about five minutes at a sink.
Fill a basin with cool water. Add a small amount of detergent made for silk or delicates. Swish the case through, give any marked spots a gentle rub between your fingers, and leave it two or three minutes. Rinse in clean cool water until it runs clear. Do not wring. Lay the case on a dry towel, roll the towel up and press to take the water out, then hang or lay it flat somewhere with air movement and no direct sun.
Skip the tumble dryer entirely. Heat and tumbling are rough on silk. If you want a crisper look, iron on low heat on the reverse side, though most people find silk drops its creases as it dries.
The two pack helps here. One on the bed, one in the cupboard, and you rotate. You are never stuck waiting for a case to dry.
Who this suits
If you have never slept on silk and you are curious, 25 momme is a good place to start because it is substantial enough that you actually feel the difference. If you already sleep on 19 momme and want something that lasts longer, this is the upgrade.
A pair of plain white cases is also the safe answer for a gift, because there is no colour or taste to guess at. And it is an easy choice for a spare room, where you want something that looks considered without having to coordinate anything.
The main people it does not suit are those who genuinely will not hand wash. Be honest with yourself on that point.
The short version
Two standard pillowcases, 20 x 26 inches (51 x 66 cm), in 100% mulberry silk at 25 momme on both faces, in solid white, with an invisible zip. Heavier than the usual 19 momme offering, which means more body and better wear. Hand wash in cool water, dry in the shade, no tumble drying.
Measure your pillow before you order. That one step prevents almost every problem a silk pillowcase buyer runs into.