Your garment has shrunk in the tumble dryer
Short answer: Heat makes the fibres contract. Dampen the garment again, gently stretch it back into shape while wet, and let it dry flat away from any heat source.
Why heat shrinks the fabric
During manufacturing, the yarn gets stretched, and that tension stays in the fibres. Heat and movement release the tension, and the stitches pull inward. That is why a garment shrinks the most the very first time it gets tumble dried hot, and less each time after that.
Stretching it back out
Soak the garment in lukewarm water with a little hair conditioner for twenty minutes, so the fibres turn soft and easier to shape. Press the water out without wringing. Lay it flat on a towel and pull it gently in length and width, a bit at a time, then let it air dry flat.
How much you can get back
Expect to regain most of one size if the damage is recent and the garment has only been through a hot dryer cycle once. Tumble dried hot many times over, the shrinkage sets in and stretching only gains a little back. Shirts and t-shirts respond best, ribbed trims respond worst.
Avoiding it next time
Wash at thirty degrees, tumble dry on the coldest program, and take the garment out while it is still slightly damp. Even better is letting it dry flat or on a line with no heat at all. See bamboo t-shirt for women and bamboo clothing for women.
Difference by cut and fabric
Closer fitting, densely knit styles generally shrink less visibly than loose, thin pieces, because there is less tension to release in the yarn to begin with. A wide dress or a loose set therefore shows shrinkage more clearly than a fitted t-shirt made from the exact same material.
Drying several garments safely at once
Sort laundry by fabric type before tumble drying, so thin bamboo pieces do not share a program with heavy towels or jeans that need more heat and time. A shorter, cooler drying cycle in a less full machine gives garments more room to move freely instead of getting pressed together.
Shrinkage relative to a garment's age
A brand new garment carries the most unreleased tension in the yarn and shrinks the most on that first hot tumble. After three or four washes at the right temperature, most of the tension has released naturally, and further shrinkage becomes markedly smaller even with an occasional too-hot cycle.
When only part of the garment has shrunk
Cuffs, hems and neckline are often knit tighter than the rest and therefore shrink differently from the main fabric. That leaves a garment that looks uneven even though it fits overall. Dampen and stretch exactly those tighter edges separately, while keeping the rest still, for a more even result.
See also
If this keeps happening with the same type of garment, choosing a quality that handles dryer heat better from the start can help. See bamboo clothing for men for alternatives with a slightly heavier knit and a more stable fit over time.
Frequently asked questions
Does bamboo viscose shrink more than cotton
They are fairly close in that regard. Both shrink the most from dryer heat, not from ordinary washing in water alone at a low temperature setting.
Can a shrunk garment be ironed back out
Only temporarily. Ironing smooths the fabric in the moment, but the fibres contract again at the next wash if the same high heat gets used.
How much does a garment typically shrink
Often around a couple of percent with correct washing at low temperature, and markedly more with high dryer heat, especially already on the very first attempt.
You can find the full range at Bamboo-Clothing.com.
