I used the Iris Knickers pattern from Tilly and the Buttons which may be the only underwear pattern anybody will ever need.

Why wool underwear? The first time I ever gave a thought to wool underwear I was in a shop selling high-end wool athletic wear. The socks (which is what I was there to purchase) and underwear were about the only things that didn’t feel wildly outside of my budget at the time. Socks sure, but underwear, I thought, why?! Cotton seemed to me to be the ideal fabric for underwear and under $20 (maybe even under $10) seemed like the ideal price. But it got under my skin and I’ve thought about it a lot ever since. It’s now ten years later and I can tell you, I have some concrete answers for the question, why wool?

Test subjects waiting for a workout. RWS merino wool and Paapii organic cotton jersey

Before I launch into why wool underwear let's talk about why not wool underwear. I had some misconceptions about the subject that I want to address right away. First and most obvious, the price. A pair of conventional ready-made wool undies will run about $30 and RWS (Responsible Wool Standard) wool undies about $35. The wool that we have available at Bolt that is suitable for underwear making is RWS merino knit. At a whopping $56 per yard, it’s easily one of the most expensive fabrics in the shop. However, with careful pattern placement, I was able to get 2 pairs out of a half yard. This puts the price at $14 per pair, slightly more with elastic trim. That’s less than half of what a ready-made pair of merino wool underwear will run you and about the same as what a ready made cotton pair might run. RWS wool costs a little more but it is more sustainably and humanely produced (I won’t cover the subject here but suffice it to say that bad things sometimes happen to sheep on conventional ranches).

My next doubt about wool underwear is that it would be maddeningly itchy. It’s true that some people are very sensitive to wool so it’s not for everyone. Merino tends to be less irritating, especially when it has been washed. This brings me to my next qualm, washability. In the name of science, I washed a 54 inch (1.5 yard) piece of our RWS merino knit, in warm water, and then tossed it into a low heat dryer. When it came out it was a little softer but, more importantly, it measured out of the dryer 53 inches. I pressed it lightly and it returned fully to 54 inches. I wash everything I make in cold water and air dry so I’m not worried about further shrinkage, but I feel pretty confident that these undies will be adequately washable and won't become unwearable if they accidentally wind up in the dryer.

Another concern that I had was more specific to the fabric that I was using. I was worried that the RWS merino we carry, which is relatively thin, would not be strong enough for underwear. After doing a little research though, I learned that merino is considered to be about 7 times stronger than cotton and has more natural stretch as well. I set about testing my washed merino comparing it to a comparable weight cotton spandex jersey. I cut two pieces of jersey, the merino and an organic cotton with 5% elastane to exactly the same size and then attempted to destroy them by stretching. The merino was markedly more stretchy and popped right back into exactly the same shape and measurements. The cotton jersey did not perform nearly as well.

It was not a good day for the cotton sample.

Lastly, my notions about wool apparel, back then, were that it’s only worth the expense if it’s keeping a critical part of me warm. Feet? Absolutely. Anyone who doesn’t wear wool socks in the winter in the Pacific Northwest is a masochist, in my opinion. But underwear? I just couldn’t imagine it would make a difference.

So, I’ve come to the heart of the question then, why wool underwear? It turns out that keeping you warm is not all that wool actually does. Wool does keep you warmer when it’s cold out but it also wicks sweat away from the skin keeping you more comfortable when its warm. Wool also resists odors, a handy feature for a pair of undies. In fact, wool has antimicrobial properties, which makes it an excellent choice for people who are prone to infections. But the reason I became obsessed with wool underwear is because I hike, run, bike, and snowshoe in the cold and damp Pacific Northwest. Cotton is about the worst thing you can wear if you are going to be in the elements, getting wet, from sweat and/or precipitation. Unlike wool, when wet, cotton loses any insulating properties it may have had and it takes a long time to dry. It winds up holding moisture against the skin. Wool stays comfortable, even when wet, and it dries quickly. Because I am a physically active person, there is actually a good amount of lycra in my life. I’ve been seeking ways to stop using products, like lycra, that produce microplastics and merino is a far more sustainable option for athletic wear. Wool uses significantly less water to produce than cotton and RWS wool in particular has a smaller environmental footprint overall.

So there you have it, all of the reasons I’m oddly obsessed with wool underwear. Do you own a pair? What do you think about them? Are you curious to try it?