Here’s what you need to know about separating laundry: Separating by colour matters because dyes can bleed, with red and blue fabric causing the most trouble, according to Mary Zeitler, a consumer scientist at Whirlpool Corporation’s Institute of Home Science. “However, after a few washes, dyes become less likely to release and transfer to other clothing,” she explains.
Put simply, separating laundry prevents unwanted colour transfer—but only if the clothes are going through their first few washes.
How you wash your clothes also makes a difference: Dyed trousers (like jeans) will stay blue (or black) longer when they’re washed inside-out, because their outer-dyed surface won’t rub against as many other clothes. Using cool water in the wash can also help cut down on bleeding for all colours.
Of course, few of us actually consider separating laundry. For most of us, the way in which we do our laundry evolves as we mature into high-functioning Homo sapiens: the Neanderthal shoves as many dirty towels and undershirts into the communal washing machine as can possibly fit and hopes to remember to take clothes out of the dryer before an impatient cohort tosses them on the ground; the Cro-magnon begins to experiment with dry cleaning; and the fully evolved launderer considers colour, temperature and fabric before hitting the “permanent press” button.
But if separating laundry sounds like too much work, just wait until clothing joins the evolution game, and becomes stain-free and self-cleaning. If the science is right, we’re not far from it.