Glerups slippers are made from a single piece of thick felted wool. When we first tested them, in 2017, we took our top four wool-slipper candidates to the textile-testing lab at the Fashion Institute of Technology, in New York. There, we cut swatches from each one and used FIT’s equipment to test the tensile strength, by measuring how much force it took to rip the fabric.
The sample from our Glerups slippers never broke. At 300 pounds of force, the fabric dented and then temporarily halted the device.
Many slippers have seams and glued-in insoles. A Glerups slipper uses a single piece of felt, so there are fewer spots that might rip or wear out. The wool insole is also felted into the shoe (a process in which the fibers are permanently interlocked), and therefore it’s much less likely to detach. Over time, the calfskin soles will get shiny, but after five years, mine have yet to pop a stitch. Another Wirecutter editor told me that after 3½ years of hard wear, her slip-ons started to unravel at the back of the heel. She opted to replace them with the boots and adores them.
Wool is a fantastic material for footwear because it repels dirt and odor. Sheep’s fleece naturally contains an oil called lanolin, so felted wool doesn’t absorb spills or stain like other slippers I’ve owned. I wear my light gray pair every morning as I sleepily splash coffee and milk and make my kid’s lunch, and they have no visible staining. If I do spill something major on them, I use a damp rag to wipe it away or run the slippers under the tap, and it usually comes right off. If you need more cleaning power, the company recommends using mild soap or vacuuming out dust.
Glerups recommends wearing its slippers with bare feet; wool absorbs moisture and keeps skin dry, so there’s little chance bacteria (and therefore odor) will build up. I prefer wearing them this way; the wool feels soft and smooth—never itchy—against my bare skin. However, other Wirecutter staffers like wearing their Glerups with socks, and they say pairs they’ve worn exclusively with socks seem to hold up longer.
