How drying time is measured in a laboratory
Short answer: Drying time is measured by weighing a dry sample, adding a known amount of water and placing it in a room with fixed temperature and humidity. The sample is then weighed at set intervals until it is dry again.
Why drying time is measured
Clothes that dry quickly are easier to live with day to day, both on the washing line and after a workout. But it is hard to compare fabrics by feel alone, because drying depends on so much. A laboratory measurement gives a number that holds across samples.
The sample is weighed dry first
You start by weighing the sample so you know the starting point. Then a known amount of water is added, so all samples start equally wet. Without that you would not know whether a fabric dried slowly because it was thick, or because it had simply been wetted more than the others.
The room must be the same every time
Temperature, humidity and air movement control evaporation. Without fixed conditions, two measurements cannot be compared. That is why the sample goes into a room where all three are held constant. A sample in a warm, dry room will always dry faster than one in a cool, damp room. See Bamboo Basics.
Weight is the clock
You follow when the weight is back at the starting point. The sample is weighed at set intervals, and each weighing is a point on a curve. When the weight has returned to the dry weight, the sample is dry. You do not have to guess whether it feels dry, since you can read it on a scale.
The curve shows the pace
The curve between wet and dry shows how fast it went. Some fabrics lose most of the water quickly and take long over the rest, while others dry evenly. Two fabrics can end up dry at the same moment but have taken quite different routes. You only see such details on the curve.
Thickness matters more than fibre
A thick fabric holds more water and dries more slowly, whatever fibre it is made from. So it is not fair to compare a thick jumper with a thin T-shirt and blame the fibre for the difference. To compare fibres, the thickness must be equal. See JBS and JBS of Denmark.
How much water is left
The more water in the fabric at the start, the longer drying takes. That is why it matters how hard the clothes were wrung or spun before hanging. The laboratory removes that variation by adding the same amount of water each time. At home, your washing machine decides the starting point.
Why the laboratory is not the home
The laboratory number does not correspond directly to drying at home. There, drying time depends on the room, the air and where the clothes hang. A number is best as a comparison between fabrics, not a promise of how many hours your clothes take. It tells you which fabric is fastest, not how fast.
How to dry clothes faster at home
Spin hard so there is less water to evaporate. Hang clothes with good space between them so air can move around. Choose a room with an open window or an airy spot. Thin clothes usually dry fastest, so hang thick items first and do not pile them together.
Frequently asked questions
Does the number match drying at home
Only as a comparison between fabrics. At home it depends on the room, the air and where the clothes hang. The laboratory tells you which fabric dries fastest, but not exactly how long your clothes will take.
Does thin clothing always dry fastest
Usually yes, because there is less water to evaporate. But air, warmth and where the clothes hang matter a lot too, so two equally thin garments can dry differently depending on where you hang them.
Does it help to spin harder
Yes. The less water that is left, the shorter the drying time. Spin as hard as the garment allows according to its care label, and hang the laundry up straight away.
You can find the full range at Bamboo-Clothing.com.
