Fran Kozen and Larissa Shepherd, experts in fiber science and apparel design at Cornell University, say snow washing appeals because wool is prone to shrinkage and rugs and blankets can be difficult to launder, but note there are caveats to consider.

Benefits:

• “As the wool will not be wet, there is no danger of shrinkage.” (Kozen)
• “When washing wool, you don't want much agitation and heat because that can cause the scales to open and, if allowed to dry with heat, it would felt.” (Shepherd)

Works best when:

• “It must be very cold, and the item should be cold before it is put in the snow.” (Kozen)
• “The snow must be the dry, fluffy sort.” (Kozen)
• “Brushing the item lightly with the slightly abrasive dry snow crystals helps remove light surface dirt.” (Kozen)
• “Snow washing likely wouldn't work well on scoured or mercerized wool, where the lanolin has been removed.” (Shepherd)

What it won’t do:

• “Snow washing will not remove stains and heavy soil.” (Kozen)
• “It won’t do anything for synthetic activewear, which holds odors.” (Kozen)
• “The most-used natural fiber, cotton, has a ribbon-shaped structure that is good at trapping dirt; snow washing may remove some surface dust, but not deep stains.” (Shepherd)

If snow isn’t in the forecast:

• “In many countries bedding is hung out to air regularly. Snow washing may give the same effect as a little shaking and UV exposure.” (Kozen)