Here’s what you’ll learn when you read this story:

• Procter & Gamble funded a study of wash cycle length that found colder and shorter is better for clothes.
• Fabric dye density and lifespan is separate from issues like germs and bacteria in the wash.
• Cold, short washes reduced shed microfibers and transferred dyes.

Scientists from the University of Leeds—and, it should be mentioned, Procter & Gamble—say the best way to keep clothes looking fresh for as long as possible is to use the coldest, shortest wash cycle.

The detergent manufacturer joined with lead author and design school instructor Lucy Cotton (yes) on a study of the way machine washing causes fabrics to spray microfibers. These lost fibers can cause premature garment aging and weaken fabrics.

In the published paper, researchers used dozens of t-shirts from a specific U.K. activewear seller representing a handful of brands like Gildan, Russell, and Hanes. Scientists ran washing machines empty at first to ensure no ridealong microfibers were inside, then collected water from the entire cycle to make sure all newly released microfibers were captured.

The resulting wash water was evaporated, dried completely, and then weighed. The scientists measured dye hold and transfer using swatches of “receiver” fabric in each load, with their color gauged before and after the wash.

After a battery of tests with different colors and materials of t-shirts at different wash temperatures and cycle lengths, the results were clear. From the study:

“[T]here is significantly greater colour loss observed for the 40 °C Cotton Short (85 min) cycle in comparison with the Cold Express (30 min) cycle. These observations provide evidence that in a ‘real’ situation increases in washing time and washing temperature increase colour loss over repeated laundering.”

The scientists also measured how much dye changed from darker colors to lighter ones, which is what leads to greying t-shirts and dimming of colors on bright prints, for example.

“Considering the effect of colour transfer over repeated laundering, it was observed that for most white receiver fabrics, significantly greater colour transfer to the tracer fabrics was observed for the 40 °C Cotton Short (85 min) cycle in comparison with the Cold Express (30 min) cycle. These observations provide evidence that, in a ‘real’ situation, increases in washing time and washing temperature increase dye transfer.”

When it came to microfibers, the same relationship bore out: higher temperature and longer time meant more microfibers, whether the fabric of the t-shirt was cotton or a polyester blend. And the release of these fibers never let up.

“What is also evidenced is that on the eighth and [16th] wash that significant numbers of microfibres are still being released from the fabrics, suggesting that there is a consistent mechanism of microfibre generation and release throughout the life of the fabrics,” the researchers wrote.

These researchers conclude that the best wash cycle is a modified Leviathan: gentler, colder, and shorter. By reducing time and temperature, they say, we can reduce the amount of microfiber pollution released into the general water cycle, the amount of waste soap, and the carbon footprint of our washer activity.

Teaming with Procter & Gamble, which released its first cold-water detergent to much ballyhoo in 2005, is a canny financial move. P&G funded the research and added its two cents about its advanced detergents in the press release. But the research appears in Dyes & Pigments, a peer-reviewed journal, and constituted Cotton’s Ph.D. project—regardless of the corporate cold water.

Caroline Delbert is a writer, avid reader, and contributing editor at Pop Mech. She’s also an enthusiast of just about everything. Her favorite topics include nuclear energy, cosmology, math of everyday things, and the philosophy of it all.