The Science Behind Cool-jams Sleepwear

The Science Behind Cool-jams Sleepwear

What Is Kottinu?

Kottinu is a technical synthetic (engineered polyester microfiber) built for moisture management, durability and cooling. It was made for demanding professional uses such as firefighter base layers and medical scrubs, and is now crafted for hot sleepers and for nights with night sweats or hot flashes. Kottinu is the fabric behind the Cool-jams NightCool collection (formerly known as Classics). It feels like super soft cotton, but it behaves like a performance fabric: it pulls sweat off your skin, dries in minutes, and carries body heat away with it.

This page is the technical explanation of how that works. If you just want the short version and the specs, see our Kottinu fabric page.

How Was Kottinu Developed?

Kottinu was engineered as a technical performance fabric long before it reached sleepwear. The brief was a fabric that looked and felt like cotton but added wicking ability, temperature regulation, quick drying ability, antimicrobial longevity and effectiveness, anti-pilling, washability, breathability and wearability. That combination is why it was specified for firefighter base layers worn under turnout gear and for medical scrubs, where fabric has to perform shift after shift and survive industrial laundering.

That same engineering was later brought to sleepwear. Our customers tell us that once they've tried Cool-jams moisture-wicking performance sleepwear, they will never sleep in anything else again.

Moisture Transference System (MST)

MST microfiber technology uses very fine fibers which are made into long strand fibers called filaments. Each filament is less than 1 decitex in measure, finer than a strand of human hair. Five to 8 filaments, each filament having slightly different performance capabilities, are twisted together to form a fine thread. Due to the unique blend of filaments, and their configuration within the thread, this creates a greater surface area for moisture to travel along the thread. These threads are then knitted together in a specific pattern which increases the speed of moisture movement through the material.

MST is a three step process:

  1. as the body perspires, moisture is transferred through the material from the skin to the outer layer of clothing, a process called moisture absorption or wicking;
  2. the moisture spreads over the surface area (moisture transport or disbursement);
  3. the disbursement process allows the outer air to evaporate the moisture (moisture drying or evaporation).

As moisture is pulled away from the body it carries with it the body's built up heat, helping to regulate body temperature. This is an invaluable process as it also minimizes excessive temperature swings in the body during sleep. MST technology provides body heat regulating while minimizing energy expended to keep the body cool and comfortable. For a plain-language explainer, read how moisture-wicking fabric works and what moisture-wicking really means.

Cool-jams fabrics disperse moisture across a large surface area for faster drying and wearer comfort. The primary benefit is the MST technology, which keeps moisture moving away from your skin through the night.

Why Kottinu Lasts Up To 6 Times Longer Than Cotton

Kottinu is engineered to last up to 6 times longer than cotton sleepwear. That durability is not a coating or a finish that washes out. It comes from the fiber itself, and it is the direct result of building sleepwear from a technical performance fabric instead of a natural one.

  • Higher tensile strength. Kottinu is a continuous engineered filament. Natural fibers like cotton are short staple lengths spun together, so they shed, thin and weaken with every wash and wear cycle. A stronger fiber simply survives more of them.
  • Anti-pilling by design. Knit cotton and knit bamboo pill as loose surface fibers tangle into bobbles. Kottinu's microfiber structure lets distressed surface hairs break away cleanly, so fresh fiber sits at the surface. The fabric keeps its smooth hand instead of turning rough and bobbled.
  • It keeps its strength when wet. Regenerated cellulosics such as viscose and viscose from bamboo lose a significant share of their strength when wet, which is precisely when sleepwear is under the most stress: night sweats, and the wash cycle itself. Kottinu does not weaken this way.
  • It holds its shape and color. Because the fiber resists abrasion and stretching, necklines, hems and prints stay sharp instead of sagging and fading after a season.

This is why performance fabrics dominate activewear and professional workwear, and why we brought one to sleepwear. Cotton and bamboo knits are comfortable on day one. Kottinu is built to still be comfortable, smooth and the right shape years later.

Kottinu vs Cotton vs Bamboo: How Sleepwear Fabrics Compare

All three feel good in the shop. They behave completely differently once you actually sweat in them.

  Kottinu (technical synthetic) Cotton Viscose from bamboo
Moisture handling Wicks sweat to the fabric surface Absorbs and holds it against skin Absorbs and holds it against skin
Dry time Minutes Slow Slow
Strength when wet Unaffected Holds up well Loses significant strength
Pilling Resists pilling by design Pills with wear Pills with wear
Garment life Up to 6x cotton Baseline Shorter than cotton
Best for Hot sleepers, night sweats, hot flashes Mild sleepers who do not sweat much Those who want softness above all

Note on bamboo: fabric sold as "bamboo" is chemically viscose, and the plant's original properties do not survive that process. It is an absorbent fiber, not a wicking one, which is why bamboo sleepwear can feel clammy once a night sweat starts.

Capillary Action and Air Flow Management

Capillary action is the movement of moisture (liquid) along the surface of the fabric (solid) caused by the attraction of moisture molecules into the fabric molecules. Maximizing the capillary action of the fabric increases its ability to absorb moisture off the body to its outer surface. Cool-jams fabrics disperse moisture over a large surface area. Once on the surface of the fabric the vaporization of moisture molecules begins.

MST technology can be constructed to suit the performance characteristics for the conditions of use. Fabrics can be constructed to reduce or accelerate air flow (e.g. in cooler conditions where tighter weaves and increased density allows for warmth to be captured and retained while allowing for moisture disbursement).

Kottinu MST diagram showing the three step moisture transference system: moisture absorption, moisture transport and moisture drying, plus the Bact-Out antibacterial finish

Antimicrobial Technology

Cool-jams® proprietary antimicrobial technology enables superior odor and fiber degradation resistance in our fabrics through the use of a powerful yet natural antimicrobial agent. The Cool-jams® antibacterial treatment is integrated into the fabric in a manner which allows for complete protection of the fabric and has been proven to be consistently effective with no tendency to cause discoloration. It is environmentally friendly and EPA approved.

The superior performance of this new generation antimicrobial technology has been achieved by combining application expertise with proprietary nano-technology manufacturing processes. The ultra-fine particles adhere more effectively to the fabric for longer protection and is 100% environmentally friendly.

Laboratory results confirm that the antimicrobial properties of our proprietary antibacterial agent remain strong after 50 or more machine washes, a powerful benefit for consumers of sports and leisurewear. In trials, using typical application processes on Cool-jams fabrics, the bacterial kill rate after 50 machine washes was 99.9%.

With Cool-jams® technology your Cool-jams NightCool sleepwear will always stay fresh and odor free. Want to keep performance fabric at its best between washes? Here are tips on how wicking clothing works and how to keep wicking clothing fresh and odor free.

Shop the Fabric

Frequently Asked Questions About Kottinu Fabric

What is Kottinu fabric made of?

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.

Does moisture-wicking sleepwear really keep you cooler?

Yes. Instead of absorbing sweat and holding it against your skin the way cotton does, Kottinu pulls moisture to the surface and lets it evaporate quickly. As that moisture leaves, it carries body heat with it, helping regulate your temperature and reduce the swings that wake you at night.

Does Kottinu really last longer than cotton?

Yes. Kottinu is engineered to last up to 6 times longer than cotton sleepwear. As a technical performance fiber it has higher tensile strength than cotton and resists pilling by design, so it keeps its smooth feel, shape and color through far more wash and wear cycles. It also holds its strength when wet, unlike viscose and viscose from bamboo.

How is Cool-jams fabric different from cotton?

Cotton absorbs moisture but dries slowly, trapping 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. You can read a full fabric comparison with cotton and polyester for the details.

Is Kottinu better than bamboo sleepwear for night sweats?

They behave very differently. Viscose from bamboo is an absorbent fiber, 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 evaporates. If your issue is softness alone, bamboo is pleasant. If your issue is sweat, a wicking fabric is doing a different job.

Is Kottinu breathable?

Yes. Breathability is engineered into the knit construction, not just the fiber. The fabric architecture allows continuous air movement across your skin rather than trapping a layer of warm, humid air the way dense weaves do.

Is the fabric soft, or does it feel like a typical synthetic?

It feels like soft, lightweight cotton, without the sticky hand-feel of many synthetic wicking fabrics, which is exactly what the fabric was engineered to achieve.

Does the cooling and odor control wash out over time?

No. The wicking performance is built into the structure of the fabric, not a coating, and lab testing showed the antimicrobial protection remained 99.9% effective after 50 machine washes.

Is Cool-jams NightCool Right For You?

Cool-jams NightCool is sleepwear, not a medical treatment. What it does is manage moisture and heat, which is why it tends to help in any situation where you wake up hot, damp, or both. Here are the situations customers ask us about most.

Are Cool-jams good pajamas for night sweats?

Yes, 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 then wake up damp, and often cold once the sweat cools. Kottinu pulls that moisture off your skin and out to the fabric surface where it dries in minutes, so there is far less of the damp-then-chilled cycle that breaks up your sleep. Read more on what causes night sweats.

Are these good pajamas for perimenopause?

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. Cool-jams NightCool will not change what your body is doing, but it does change what you are lying in: sweat gets moved off your skin and dried instead of pooling in the fabric. Many customers tell us the practical win is not having to get up and change in the middle of the night. Start with our menopause and perimenopause cooling pajamas.

Are these good pajamas for menopause and hot flashes?

Yes. A hot flash produces a rush of heat and then sweat, and the discomfort afterwards usually comes from the sweat sitting in your sleepwear. Because Kottinu wicks and dries in minutes, and because evaporation carries body heat away with it, the fabric works with your body's own cooling process instead of against it. See our guide to the best sleepwear for hot flashes and our menopause sleep products buyer's guide.

Are these good pajamas for women who sleep hot?

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.

Are these good pajamas for men who sleep hot?

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. If you want the background, read what causes night sweats in men.

Are these good travel pajamas?

Yes, Kottinu 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 because it dries in minutes you can rinse a set in a hotel sink at night and have it dry by morning. The Bact-Out finish also helps the fabric resist odor so a set stays fresher between washes, which matters on longer trips and when you are packing light. See our travel-friendly pajamas and what to look for in travel sleepwear.

Are these good pajamas for nursing mothers?

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.

Are these good pajamas during cancer treatment?

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. Our sleep solutions guide for patients undergoing cancer treatment covers this in more detail.

Are these good for hot climates and summer?

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. Kottinu also works without air conditioning, which is why it travels well to warm destinations.

Can you wear NightCool in winter, or is it only for hot sleepers?

You can wear it year-round, and a lot of customers do. Temperature regulation works in both directions: the fabric stops 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.

Should I choose NightCool or DayBasics?

Choose NightCool if your issue is heat or sweat: night sweats, hot flashes, perimenopause, or simply sleeping hot. That is what Kottinu is engineered for. Choose DayBasics if you want soft, lightweight everyday sleepwear and loungewear without the performance layer. Our DayBasics vs NightCool guide walks through both.

Care and Practical Questions

How do I wash Cool-jams NightCool sleepwear?

Machine wash warm or cold with like colors, no bleach, tumble dry low or hang to dry, and iron low if you iron at all. No special detergent is needed. Full instructions are on our sleepwear care page.

Can I use fabric softener?

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 fiber itself.

Do Cool-jams pajamas shrink?

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.

How quickly does the fabric dry?

Minutes rather than hours. That applies both to sweat during the night and to washing, which is what makes it so practical for travel and for anyone doing frequent laundry.

What sizes does Cool-jams NightCool come in?

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 sleepwear size charts for measurements before ordering.

Do the men's and women's lines use the same fabric?

Yes. Both the men's and women's NightCool lines are made from the same Kottinu fabric with the same MST moisture system and Bact-Out finish. Only the cuts and styling differ.