Casper's mattress testing is so thorough, it even invented a special machine to simulate back sweat

When Casper first launched three years ago, it was a small startup with a single engineer working on product development.

Three years later, cofounder and chief product officer Jeff Chapin leads a team of 35 people at Casper's new research and development lab in San Francisco.

The lab handles nearly every aspect of testing Casper's lines of mattresses, which now includes the new Casper Wave. While Casper outsources some of its ergonomic testing, everything from prototyping to heat testing takes place in-house.

"One of the things that was really important to us was to have better tools and better space for building, prototyping, and testing," Chapin told Business Insider. "We hope to double in size here in the next six to 12 months just to be able to do all the things we want to do."

Here's everything housed inside Casper's lab:

• Collaborative space for checking out bedding samples and new materials, do project planning, and host strategy meetings
• Space for foam fabrication, textile and pattern cutting, packaging fabrication, and wood and metal shops for furniture projects
• Test labs for the how the memory foam holds up in terms of firmness, durability, comfort, rebound, and recovery
• Thermal testing labs for dry and humid heat

What Casper is trying to understand with all of its tests is how its products behave over time, and whether they can stand up to the elements. Chapin said Casper even invented a new, very specific machine to test mattresses: The sweating thermal sacrum machine, AKA a lower-back-sweat simulator.

The lower back is typically the hottest, sweatiest part of your body when you sleep, according to Chapin, so the machine has hot plates that leak a small amount of moisture over time. That way, Casper can see if its mattresses hold up for hot sleepers.

Casper also uses human subjects to test out its mattresses, using test kits both at its in-house bedroom in San Francisco and at the homes of employees, their friends and families, and a group of Casper testers. The company measures things like how humidity levels in the room affect the mattress and what the temperature is like under the covers. Casper even knows how often and at what time its subjects typically get out of bed at night, and whether they're too hot or too cold while they're sleeping.

All of this goes into designing and building Casper's mattresses, which landed the company $200 million in sales last year.

Despite the company's success - and something of a cult following - Chapin acknowledged that all that testing can seem a bit over-the-top to an outside observer: "It's a lot for a big chunk of foam."