Classic Gear: Therm-A-Rest

Camp on the Pacific Crest Trail in 1982, my Therm-A-Rest in the foreground

Fourth in the Classic Gear series that appeared in The Great Outdoors last year. This time, a mattress that revolutionised sleeping comfort.

Back in the 1970s, when I began backpacking, sleeping mats were all closed cell foam. These were bulky and not very comfortable but also nearly indestructible and good insulators. Bright yellow ones – the ubiquitous Karrimat – could be seen strapped on every backpackers pack. However the same decade saw change coming from far away Seattle in the Pacific Northwest, where, in 1971, climber John Burroughs suggested to two mountaineering friends that he’d like a better mat. At the time engineers Jim Lea and Neil Anderson had just been made redundant so they were able and keen to take up this idea.

Therm-A-Rest prototype in sandwich maker

The breakthrough that would lead to the first ever self-inflating mat came when Jim Lea was gardening and noticed that the foam cushion he was kneeling on let air out when he shifted his weight. Seal that foam in an airtight fabric and you’d have a comfortable mat he realised. To make a prototype he and Anderson used a sandwich maker to melt the fabric onto the foam. They then added a valve so the air could be sealed in and squeezed out and their first mini mat was complete. 

First series Therm-A-Rest

 

Further work improved and refined the design, which was patented in 1972. Two years later production began under the name of their new company, Cascade Designs, founded by Burroughs, Lea and Anderson. 

As with many innovative products in those pre-Internet days knowledge of the Therm-A-Rest mat was slow to spread and it didn’t arrive in the UK until the end of the 1970s. In the 1980s it became popular worldwide however. A manufacturing plant was opened in Ireland in 1984. In the beginning there was just one model, simply called the Therm-A-Rest. It was 47 inches (119cms) long and weighed 1lb 7oz (652 grams). This was considerably heavier than a closed cell foam mat. However the difference in comfort was so great that I took one on my Pacific Crest Trail walk in 1982 and found it excellent. It lasted the whole trip, was very comfortable and kept me warm sleeping on snow in sub-zero temperatures at altitudes above 10,000 feet (3050 metres). I also liked the fact that when compressed it was compact and could be stored inside my pack rather than strapped on the outside. I used one again on the Continental Divide Trail in 1985. 

Early Therm-A-Rest advertisement

That first mat had a solid foam core, a plain nylon shell, a metal valve and a rectangular shape. Today the name Therm-A-Rest covers a whole family of mats in different weights and lengths that have cored foam, curved sides, different fabrics top and bottom, plastic valves, and different models for women and men. The closest to the original mat is probably the Prolite Plus. The 72 inch (183cms) Regular size weighs 592 grams. 

Today there are many companies making self-inflating mats and it’s difficult to realise just how revolutionary the first Therm-A-Rest was. All the current mats derive from that 1972 model though and from the ideas of a climber kneeling on a gardening cushion. Without Therm-A-Rest wild camping would be far less comfortable.