Why sweat breaks elastic down
Short answer: Sweat contains salt, acid and fat. The salts draw water out of the thread, the acid attacks the bonds, and the fat softens the material. Together they shorten the life of the elastic.
Salt dries out the thread
When sweat evaporates, salt crystals are left in the fabric. They draw moisture out of the elastane and make it more brittle. A brittle thread cannot draw back the way one in good condition can, so the waistband slowly loses its ability to hold its shape after a day of sweat.
The acid works on the bonds
Sweat is mildly acidic, and over time that weakens the chemical bonds in elastane. It happens slowly but steadily, each time a garment is worn and not washed afterwards. Nothing shows from one day to the next, but the effects add up and finally appear as slack elastic. See bamboo sweatpants for men.
The fat softens the material
Sweat also contains fat from the skin. The fat settles in the fabric and softens the material, so the elastane becomes less springy. It sits in the fabric together with the salt and acid, and it is an ordinary wash that removes it, more than a quick rinse in water.
Why sweaty clothes must be washed
Leaving a sweaty garment until the next day gives the salts and acid many extra hours to work. A quick rinse helps, and a proper wash is better. The shorter the time sweat sits in the fabric, the less damage the elastane takes. Do not leave it in a damp gym bag or in the laundry for days. See bamboo underwear for men.
Rinsing as a stopgap
If you are out and cannot wash straight away, rinse the garment in water. That removes some of the salt and is better than nothing. A rinse does not remove the fat, though, so wash the garment properly as soon as you get home. Hang it up to dry instead of stuffing it in a bag.
Sportswear takes the hardest hit
The elastic gives up first in sportswear because sweat, heat and stretch all strike at once. Sweat pulls in one direction, heat in another, and movement stretches the thread on top. All three work against the elastane at the same time, so sportswear is often the first to lose its shape. See bamboo tank top for men.
Rotate between several pieces
If you have several pieces, each one rests between wears and the elastane can draw back together. If the same piece is worn day after day without a break, sweat and strain build up. So rotate between several, so that each has time to recover and dry fully in between.
Wash at a low temperature
Wash sweaty clothes at a low temperature and avoid the tumble dryer, because heat is an extra strain on elastane on top of the sweat. Let clothes dry fully before they go in the drawer. The better a garment is looked after, the longer the elastic lasts and the longer it can be worn without losing its fit.
Frequently asked questions
Is it enough to rinse in water
As a stopgap, yes. A proper wash also removes the fat, which a rinse does not reach, so wash the garment properly as soon as you can.
Why does the elastic go first in sportswear
Because sweat, heat and stretch strike at once. The three work against the elastane together, and that wears it faster than everyday use does.
Does it help to wash straight away
Yes. The shorter the time the salts sit in the fabric, the less damage. Wash at a low temperature and let clothes dry fully before wearing them again.
You can find the full range at Bamboo-Clothing.com.
