Why there is elastane in bamboo clothing
Short answer: Elastane is added in small amounts to give stretch and to make the garment return to shape. Without elastane, underwear and socks in particular would quickly go slack.
What elastane does
Pure viscose stretches but does not pull back again. Elastane is the fibre that gives the recovery.
How little is needed
The proportion is typically a few per cent. That is enough to hold the shape without changing how the fabric feels.
Where it is used most
Socks, underwear and leggings have the most elastane, because they have to sit close. See bamboo leggings for women.
Where it is used least
T-shirts and bedding often have little or no elastane, because they are not meant to be tight. See bamboo bedding.
Heat destroys elastane
Elastane loses its grip through heat. That is the main reason the tumble dryer is advised against. See the washing guide.
Signs of worn elastane
When the waistband no longer pulls back after a day of wear, the elastane is used up.
See also
More on the material in is bamboo clothing stretchy.
Frequently asked questions
Why is there plastic in bamboo clothing?
Elastane is a synthetic fibre, but it is used in small amounts to hold the shape.
Can you get underwear with no elastane at all?
It exists, but it loses its shape faster.
What destroys elastane?
Heat. The tumble dryer and a high wash temperature are the two biggest culprits.
