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There's an overwhelming amount of scientific evidence that tumble-drying does irreparable damage to clothes. Such is the price of convenience and lack of clotheslines. But how exactly does a dryer hurt your clothes? There are three distinctive ways dryers could hurt fabric: shrinkage, color transfer, and actual tears to the material. To fully understand how a dryer can negatively affect clothing, we researched some scientific studies detailing these effects of tumble-drying.
Did you get bigger or did your clothes get smaller?
Shrinkage is one of laundry's greatest problems. When you put in a pair of size 32/34 jeans, you expect them to come out that way, and when they don't, you're faced with a diet or trip to the mall. As an issue affecting the entire world, it was only a matter of time before people investigated shrinkage with the scientific method.
In a study, researchers took square pieces of cotton and cotton/synthetic fiber blended fabrics and marked several areas, noting the distances and angles between each mark. The researchers put the squares through various washes, following them with either an air-drying session, a high heat cycle, or a low heat cycle.
The study confirmed some common knowledge. Drying shrinks clothing twice as much as washing, and tumble-drying shrinks twice as much as air-drying.
But the study yielded some novel information: When washing or tumble-drying, temperature actually doesn't affect shrinkage. The hot washer cycle shrank just as much as the cold, and tumble-dry high shrank as much as tumble-dry low. As it turns out, the mechanical agitation and forced air was the culprit for shrunken clothing. Adjust your common knowledge accordingly.
These Colors Don’t Fade
After dimensional changes, color bleeding and fading are the next biggest problems that come with doing laundry. To investigate whether drying plays a role in color fastness, scientists tested dispersal dyes—the type used most in clothing today—to see at what temperature they sublimate. Sublimation is where a solid bypasses the liquid phase and goes straight to gas, so picture the fabric's solid dye molecules turning into gas, moving to neighboring fibers, and turning back into a solid dye. This is how bleeding and fading usually happens.
But according to the tests, most dyes don't sublimate until around 340°F. If you ever come across a dryer that gets that hot, we recommend leaving the building, since that dryer might actually be on fire. So dryers are off the hook for color fastness damage. Most dyes are just too permanent.
The Proof is in the Lint
While shrinkage and color running are the two immediately obvious negative changes dryers make to clothes, there's a more long-term and less obvious problem. Every time you put your clothes through the laundry, the system imparts microscopic damage to the fabric. By definition, microscopic damage is invisible to the naked eye, but it's easy to see the collective damage—just check your dryer's lint tray. Lint results from tiny tears in the fabric's fibers, and over time the sum of these tears cause clothing to fall apart.
Wear and Tear
To examine dryer impact on microscopic tears, researchers took hemmed cotton towels, rinsed them in a washing machine, and then tumble-dried them at high heat (150°F) and without heat. The study ran towels through 20 wet/dry cycles, measuring the tensile strength after each run. If a fabric is strong, it's in good condition.
The test results were alarming. After only 20 cycles of washing and drying, the fabric had lost about 50 percent of its tensile strength. Let's say that again: Drying fabric at 150°F only twenty times makes it twice as easy to tear.
But are your clothes safe when dried without heat? It turns out that tumble-drying without heat only results in a 24% loss, only half as bad as the hot cycles. However, it's clear that tumble-drying on low is no guarantee for longevity. To make matters worse, the tensile strength doesn’t seem to ever level out over time, so every laundry cycle pushes your clothes toward obliteration. As we saw with shrinkage, the mechanical tumbling action is the a main cause of fabric wear.
Tumbling towards the inevitable
Dryers may save you time, but at a cost your clothes must shoulder. Dryers shrink clothes, and hot tumble-drying in particular takes a toll on fabric. So if you want to try to balance convenience and protecting your clothes, you should stick to short cycle times and low heat, minimizing mechanical action and heat exposure.
Obviously, this puts dryer manufacturers into a predicament since cycle time and temperature are inversely related (the higher the temperatures, the shorter the cycle). With the current technology, their job has become finding that sweet spot where cycles are short enough to minimize damage, but not so hot so the fabric gets cooked. But until someone comes up with a better solution, we recommend keeping your most sensitive and valuable clothing away from the dryer and on the line.
Citations: Klausinger, S. L. et al., AATCC Review, 2012, pp. 51-57; Zimmerman, C. L. et al., Textile Chemist & Colorist, 1974, Vol. 6(11), pp. 52-54; Buisson, Y. L. et al., Textile Research Journal, 2000, Vol. 70(8), pp. 739-743
Photos by Flickr users snacktime2007, RaSeLaSeD - Il Pinguino, distillated, Sasha Trubetskoy