Drying wool flat rather than hanging it

Does it work?

Supported

Supported as a practice by the fibre's own trade body. The mechanism is not supported and is marked as interpretation — an unusual split worth preserving, because the instruction is reliable and the explanation everyone attaches to it is not sourced.

This is a verdict on whether the technique is effective. Whether it is safe on a particular surface is a separate question, answered below.

The proposed mechanism

The explanation below is what is offered for this technique. CleaningHQ has not found evidence establishing that this is what actually happens, and says so rather than presenting a plausible story as a finding.

Wool absorbs a large amount of water, and the weight of it acting on a fibre network that is free to deform is supposed to elongate the garment irreversibly. The account is plausible and is not stated by the source, which recommends flat drying without explaining it — so the practice is evidenced and the reason is not.

Background

A wet wool garment hung on a line or a hanger comes back longer than it went on, and the standard explanation is that saturated wool is heavy and the fibre yields under its own weight. The wool body's guidance recommends flat drying after washing, plainly and without qualification, which settles the practice. It does not give the mechanism, and CleaningHQ will not attribute one to it: the stretching account is an interpretation from general fibre behaviour rather than something the source states. What the same guidance does establish is the surrounding routine — machine washing on the wool setting, described as usually gentle action at 40°C, or hand washing in lukewarm water at approximately 30°C with a ten-minute soak, rinsed first in lukewarm and finally in cold water. And it makes one claim worth noticing about shrinkage: a Woolmark-approved machine-washable garment is stated to withstand machine washing multiple times WITHOUT shrinkage, which locates the risk in the garment's construction and approval rather than in wool as such. As always the item's own care label accounts for its dyes, trims and interlinings and outranks anything general about the fibre.

What it does not do

• The source recommends flat drying and gives no mechanism, so the stretching explanation is CleaningHQ's interpretation and is labelled as one
• The page gives no tumble-drying instruction, so no position on tumble drying may be attributed to the body
• It gives no felting or shrinkage mechanism either
• A specific garment's care label accounts for its construction and outranks general fibre guidance

What to use instead

• Wool detergent — A mild, near-neutral detergent without enzymes or bleach. What the wool industry body recommends, and what it recommends against is the more useful half.