In the early 1970s, two Boeing engineers used a sandwich press to put a slice of foam between two pieces of airtight nylon and invented the self-inflating sleeping pad for campers. Therm-A-Rest still uses that basic principle today, just the sandwich machine has given way to an entire factory in Seattle. This is that production process today.
Step 1: Hadouken
These huge blocks of foam arrive at the Therm-A-Rest factory in Seattle from a local supplier. There, they immediately undergo various karate kicks, martial arts combos and WWF-worthy body slams courtesy of the staff. This isn't technically part of the production process.
Step 2: Slice The Foam
The blocks of foam are loaded onto what's basically an air hockey table. A cushion of air enables them to slide onto the platform effortlessly and, when switched from blow to suck, it then securely holds the foam brick as the platform rolls back and forth through that horizontal bandsaw blade you can just see stretched between the machine's two red towers. Starting at the top and working to the bottom, the foam is sliced into the final thickness required by the pad.
Step 3: Stamp The Shape
The next machine is basically a big cookie cutter, stamping the foam into the various lengths, widths and shapes required by the company's product range. There isn't exactly a huge industry out there producing self-inflating sleeping pads, so Therm-A-Rest has to design and make all this tooling in-house.
Step 4: Stretch The Foam And Cut The Holes
Without pre-made, bought-in solutions, Therm-A-Rest starts with its desired result, then engineers its tools backwards. Holes in the foam save weight, but if they go straight up and down, they will spoil the insulation.
So, the giant machine you see in the background here locates each piece of foam on a one-ton pallet, then compresses that foam, stretches it lengthwise, then stamps holes into it that, when the pad returns to its shape, actually pass through diagonally. That way, when you sleep on it, you "close" the holes with your bodyweight.
That simple result requires that one-ton pallet to be lifted up overhead and across for each pad stamped, starting at the bottom left and moving to the top right. It's a ridiculous amount of effort, but the result it a lighter pad that retains its warmth.
Step 5: Collect The "Dots"
The foam doughnut holes are sucked out of the press, into the duct that runs up and over the walkway, then blown into giant plastic bags. Rather than waste them, Therm-A-Rest uses the oddly shaped little pieces of foam to fill its range of camp pillows.
Step 6: Ready The Outers
Polyurethane-coated nylon in various weights and finishes arrives at the factory and is cut to size.
This lady applies the Therm-A-Rest decal, then inspects each outer for defects on a light table.
Step 7: Weld The Layers
These two guys stack each piece of foam between the top and bottom layers of PU-coated nylon, then insert them in what's basically a big sandwich press. Hot oil flows through the machine from the white pipes you see on the wall behind and around the outer perimeter of the pad. The two layers of nylon are pressed together with that heat and permanently bonded.
Step 8: Cool The Pads
The pads slide out of the sandwich press and onto this bank of box fans, where they cool for a brief period.
Step 9: Insert The Valve
This machine inserts the valve hardware, a plastic block that holds the valve and allows air to pass through the welded perimeter, then mounts the screw-on valve you'll be familiar with operating.
Step 10: Trim The Excess
The extra nylon is trimmed by hand, resulting in the final product.
Step 11: Test Inflation
Every single pad that Therm-A-Rest makes is inflated to 2psi, then stored inflated for 36 hours. If it doesn't hold that pressure, the pad is recycled. As you can see in the top photo, the factory floor is quite literally full of pads undergoing that test period.
Step 12: Dunk Test
The valves are dunked in a bucket of water to ensure their air-tightness. Any bubbles and they start over. This is one of the newer, more expensive NeoAir pads, but all Therm-A-Rests are tested the same way.
Step 13: Compress Pads For Shipping
Following the 36-hour test, the pads are placed in this wooden press, which compresses them to the minimum possible thickness. The tubes you see on the bottom right attach to the valves and vacuum the air out.
Step 14: Roll And Box
The pads are rolled by hand into a plastic sheath. The valve is left open to account for changes in pressure and temperature during shipping.
Pads are then boxed and shipped to retailers around the world. When you get yours, you just unroll it and the foam will expand, drawing air into the pad. Top that off with one or two breaths and you're ready for a good night's sleep.