The science behind Cool-jams sleepwear

Kottinu is a technical synthetic, an engineered polyester microfiber. It was developed for professional performance uses such as firefighter base layers and medical scrubs, and is now used in Cool-jams NightCool sleepwear for hot sleepers and for nights with night sweats and hot flashes.

Instead of absorbing sweat and holding it against your skin the way cotton does, Kottinu pulls moisture to the surface where air can reach it and it evaporates. Evaporation takes heat with it, which is the mechanism behind the cooler feeling. What the fabric changes is what you are lying in, not what your body is doing.

It is built to. As a technical performance fibre it has higher tensile strength than cotton, it resists pilling by design so it keeps its smooth feel, shape and colour through more wash and wear cycles, and it holds its strength when wet, which viscose and viscose from bamboo do not.

This answer used to carry a multiple. We have taken it out. The engineering behind the durability is real; a wash-cycle test we can put in front of you is not something we have, so the number should not have been on the page.

Cotton absorbs moisture but dries slowly, so it traps dampness next to your skin, and it wears down comparatively quickly. Kottinu is a technical synthetic that wicks moisture away, dries quickly and resists pilling, so you stay dry rather than damp and your sleepwear lasts. Section 04 above is the molecular version of the same answer.

They behave very differently. Viscose from bamboo is an absorbent fibre, so it soaks moisture up and holds it, which is why bamboo sleepwear can feel damp and clammy once you actually sweat. Kottinu is engineered to move moisture off your skin to the surface of the fabric where it can evaporate. If your issue is softness alone, bamboo is lovely and our own BambooSoft line is made of it. If your issue is sweat, a wicking fabric is doing a different job.

Yes, and the breathability is engineered into the knit construction rather than into the fibre. The fabric architecture allows continuous air movement across your skin instead of trapping a layer of warm, humid air the way dense weaves do. In the 2021 testing our fabric measured the highest air permeability of the five fabrics tested under ASTM D737-18, which is the number in section 06.

It feels like soft, lightweight cotton, without the sticky hand-feel of many synthetic wicking fabrics, which is exactly what it was engineered to achieve. It is not the softest fabric we sell. Our own fibre guide rates it Good for softness where the cellulosics rate Excellent, and the graph in section 06b shows that trade rather than hiding it.

The wicking does not. It is the structure of the fabric and not a coating, so there is nothing on it to wash off.

The freshness is a treatment. Bact-Out is applied to the fabric to inhibit the growth of odour-causing bacteria on the fabric, which is what keeps a garment smelling fresher between washes. It is not a health product, and it does nothing to bacteria on your skin.

We used to publish a percentage and a wash count for that treatment. Both are gone. The mechanism is described in section 05 and it is described precisely, which is the version we can stand behind.

Yes, and this is the single most common reason people find us. During a night sweat your body produces more moisture than cotton can move, so cotton soaks it up and holds it against your skin. You wake up damp, and often cold once that sweat cools. Kottinu pulls the moisture off your skin and out to the fabric surface where air can reach it, so there is far less of the damp-then-chilled cycle that breaks up your sleep.

Yes, and perimenopause is often when people start looking. Temperature swings, hot flashes and night sweats can begin years before menopause itself, and they frequently show up at night first. NightCool will not change what your body is doing, but it does change what you are lying in: sweat is moved off your skin and out to where it can dry, instead of pooling in the fabric. Customers tell us the practical win is not having to get up and change in the middle of the night.

Yes. A hot flash produces a rush of heat and then sweat, and the discomfort afterwards usually comes from that sweat sitting in your sleepwear. Kottinu moves it off your skin and out to the surface where it can evaporate, and evaporation carries body heat away with it, so the fabric works with your own cooling process instead of against it.

Yes. You do not need to be in perimenopause or menopause to run hot at night. Plenty of our customers simply have a warm bedroom, a partner who radiates heat, a memory foam mattress that traps it, or a body that runs warm year-round. The women's NightCool collection covers nightgowns, nightshirts, tops, bottoms and full sets, so you can choose the coverage that suits how you sleep.

Yes. The men's NightCool collection uses exactly the same Kottinu fabric as the women's line, cut in relaxed styles built for sleep: crew neck and tank tops, boxer shorts, pants and matching sets. It is made for men who run hot year-round, sleep under a partner's preferred number of blankets, or wake up sweating.

Yes, and it is one of the most practical travel sleepwear fabrics you can pack. It is lightweight and compresses down small in a bag, it resists wrinkling so it comes out ready to wear, and it dries fast enough to rinse a set in a hotel sink at night and wear it the next one. The Bact-Out treatment helps the fabric resist odour, which matters on longer trips and when you are packing light.

Yes. Night feeds and postpartum temperature swings are a common reason customers come to us, and the same wicking and quick-dry behaviour applies. Our snap front and button front nightshirts and tops are the easiest styles for nursing access, and the fabric handles the frequent washing that comes with this stage of life.

Many of our customers are going through cancer treatment, which can bring night sweats and temperature swings. Cool-jams NightCool is sleepwear rather than a medical product, so it will not affect treatment in any way, but wicking sleepwear can make those nights considerably more comfortable and means less getting up to change.

Yes. In a warm or humid bedroom the problem is that sweat has nowhere to go, so it sits on your skin and in your sleepwear. A wicking fabric moves it out to the surface where air can reach it. It also works without air conditioning, which is why it travels well to warm destinations.

You can wear it year-round, and a lot of customers do. Temperature regulation works in both directions: the fabric helps stop you overheating under a winter duvet, and because you are not lying in damp fabric afterwards you avoid the cold, clammy feeling that follows a night sweat in cotton. Long sleeve tops, full length pants and long nightgowns give you cooler-weather coverage in the same fabric.

NightCool if you wake up hot or damp. It is the performance line and it is the fabric this whole page is about. The honest limit: it is function first, so if your goal is purely lazy-Sunday softness rather than sweat management, one of the other two will suit you better.

BambooSoft if you want luxurious softness and an eco-conscious fibre. It is viscose from bamboo. The honest limit: it is a comfort fabric, not a performance one, and it is weaker when wet and needs gentler washing.

DayBasics for simple, comfortable, value-friendly lounging and sleep. The honest limit: like BambooSoft, it is not engineered as a night-sweats solution.

Machine wash warm or cold with like colours, no bleach, tumble dry low or hang to dry, and iron low if you iron at all. No special detergent is needed.

No, and this is the one care mistake worth avoiding. Fabric softener leaves a waxy residue that coats the microfibers and clogs the fabric, which reduces how well it wicks. Kottinu keeps its soft feel without softener, because the softness is built into the fibre itself.

No. Because Kottinu is an engineered synthetic rather than a natural knit, it is dimensionally stable and holds its shape and size through washing, unlike cotton knits, which commonly shrink and relax over time.

Faster than cotton, and fast enough to matter both on a hot night and in a hotel sink. In the 2021 comparative testing our fabric recorded the fastest drying rate of the five fabrics tested under AATCC 201-2014.

We used to answer this with minutes. We have stopped, because drying time depends on how wet the fabric is, how warm the room is and how much air is moving, and no test on file measures it in minutes. The rank is the part we can show you.

The collection is cut and sized for real bodies and runs through a full range of sizes, including extended sizes on many styles. Check the size charts for measurements before ordering.

Yes. Both lines are made from the same Kottinu fabric, with the same moisture transference system and the same Bact-Out treatment. Only the cuts and the styling differ.