Is a Silk Bonnet Hot to Sleep In? Wearing One Through Summer

A 1970 US Army survival manual warned that 40 to 45 percent of your body heat escapes through your head. The figure most likely traced back to test subjects in arctic survival suits with only their heads left bare. So how much can a thin silk cap really hold in?

Not much, going by the two doctors who took that number apart in the BMJ in 2008. Had the same subjects been in swimsuits, they reasoned, the head would have accounted for no more than about a tenth of the heat lost. The face, head and chest are more sensitive to changes in temperature than the rest of the body, so your head may be quick to notice a new layer. The heat it holds in is another matter, and a thin layer of silk over your hair is unlikely to add much to it.

Is a silk bonnet hot to sleep in?

Not for most people. Silk is thin, smooth and light, and a bonnet covers only your hair, leaving your face and neck open. Our Medium and Large bonnets are double-lined, with two full layers of 19-momme mulberry silk, and together those layers weigh about 4.9 ounces per square yard, in the range of ordinary T-shirt fabric. Like anything on your head, a bonnet holds a little warmth. For many people that's more than made up for by what it takes away: a heavy curtain of hair lying across a warm neck and a warm pillow.

As far as we can find, nobody has measured scalp temperature under a bonnet, so this is reasoning from how thin fabric and long hair behave, not a lab result. But if you've slept through August with long hair loose, you probably know the feeling of peeling it off the back of your neck in the middle of the night.

Is silk a good fabric for a summer bonnet?

It's a good one to sleep in. Silk feels cool for the first moment it touches your skin, which is a pleasant way to start a hot night, and it's a natural protein fiber with a smooth, fine surface. Many people find it less clammy than polyester satin on a warm night, and silk vs satin bonnets explains why that may be, though nobody has tested it in a bonnet. Satin bonnets work well for plenty of people. If yours has felt stuffy in July, silk is worth trying.

No bonnet will cool your head down, and we don't claim ours does. Silk simply adds very little. Silk clothing in summer is a separate question, since it hangs away from the skin with air moving around it, and that's covered in is silk hot to wear?

What's a silk bonnet like on humid nights?

Humid nights are the hardest on everyone, bonnet or not, because humid air slows down one of your main ways of shedding heat. Sweat cools you as it evaporates, and as the National Weather Service explains, evaporation from the body slows when relative humidity is high. In Houston, the average dew point in July is about 72°F, and average morning humidity runs above 90 percent.

Those are also the nights long hair sticks to your neck. Tucked up inside a bonnet, it stays off your skin and off the pillow, which is a fair trade for a thin layer of silk on top. Go to bed with dry hair, loosen the opening a notch, and point a fan across the bed. Moving air helps sweat evaporate, which is what a sticky night needs most.

What about dry heat in the Southwest?

Dry heat is easier on a bonnet. The normal low in Phoenix in July is 84.5°F, but in air that dry, sweat evaporates quickly, so a silk cap is less likely to feel clammy. Evaporative coolers, which work best in the dry parts of the country, add moisture to a room as they cool it, so a house running one can feel somewhere between Phoenix and Houston at night.

Does air conditioning make a bonnet comfortable?

Yes, and most American homes have it. In the federal government's 2020 household energy survey, 88 percent of US households used air conditioning, rising to 93 percent in the South. A Cleveland Clinic sleep psychologist suggests keeping the bedroom at 60 to 67°F, and anywhere near that, a thin silk cap is unlikely to be what you notice.

How do you stay cool in a silk bonnet on hot nights?

A few small changes can make a summer night in a bonnet more comfortable.

1. Get the size right and loosen the opening. The Medium fits heads about 19.5 to 23.5 in (50 to 60 cm) around, the Large 21.5 to 25.5 in (55 to 65 cm), and both have an adjustable opening. A band that leaves a line on your forehead is too tight in any season.
2. Give long hair room. Coil it loosely rather than packing it in hard. If your hair is long or thick, the Extra Large has the same opening as the Large with extra depth through the crown, so the silk isn't pulled tight against your head.
3. Go to bed with dry hair. Damp hair under any covering stays damp for hours, and sleeping with wet hair has problems of its own.
4. Cool the room. Turn the thermostat down before bed if you can, run a fan and switch to lighter sheets.
5. Wash it more often. In hot, sticky weather, wash your bonnet every 4 or 5 days rather than weekly. A second bonnet means there's always a clean, dry one for bedtime.

One thing a bonnet shouldn't get blamed for: if you regularly wake with your nightclothes or sheets soaked, talk to your doctor. Mayo Clinic separates repeated drenching sweats from waking up sweaty because the room is hot or you have too many blankets, and the first can have a medical cause.

Can you wear a silk bonnet all year round?

Yes, and many people wear theirs every night, summer included. What a bonnet does for your hair overnight doesn't stop in July: less rubbing against the pillow, which many people find means fewer tangles and less frizz in the morning, and a style that may keep more of its shape until morning. Do silk bonnets really work? goes through what to expect.

See LS Silk bonnets, each with an adjustable opening →

The Army's 40 to 45 percent is still being repeated more than 50 years on, mostly to children in January. Your head was never where half your heat went, and a thin layer of silk over your hair has little to hold in. On the first hot night of summer, loosen the opening, turn on the fan, and leave the bonnet on.

Frequently asked questions

Do silk bonnets make you sweat?

Not usually. Silk is thin and light, and a bonnet covers only your hair, not your face or neck. On a humid night without AC your hairline may feel damp whatever you wear, so loosen the opening a notch and run a fan.

Is a silk bonnet cooler than a satin bonnet?

Many people find silk less clammy than polyester satin on a warm night, and it feels cool to the touch at first. Neither fabric cools you down, and as far as we know nobody has tested them side by side in bonnets. If satin has felt stuffy, silk is worth trying.

Can you wear a silk bonnet in summer without AC?

Yes. Go to bed with dry hair, loosen the opening, coil your hair loosely inside, and point a fan across the bed. Moving air helps sweat evaporate, which matters most on humid nights.

What's the coolest way to sleep with long hair?

Off your neck and off the pillow. A bonnet does both: coil your hair loosely on top or at the back of your head and tuck it in. If your hair is long or thick, the Extra Large has extra depth through the crown so it isn't packed tight.

How often should you wash a silk bonnet in summer?

Every 4 or 5 days in hot, sticky weather or if you sweat in your sleep, and about once a week otherwise. Hand wash it cold, or machine wash it on a gentle cycle in a mesh bag with mild detergent, then hang it or lay it flat to dry.

Why does my head sweat at night?

A warm room or heavy bedding is the usual reason, and turning the room down is the first thing to try. If you regularly wake with your nightclothes or sheets soaked, see your doctor, because repeated drenching sweats can have a medical cause.

Related reading: The Silk Bonnet Guide · Silk Bonnet vs Silk Pillowcase