Long live spiders. Or more accurately, longlivespiders. That’s the password to gain access to the guest wi-fi, as indicated by a little sign on the conference room’s whiteboard. Hanging from the ceiling is a huge lighting fixture that looks like a cumulus cloud floating in midair, but it’s actually made from hundreds of silkworm cocoons that have been wired together — each comprised of two filaments of silk nearly a mile long. The conference room is named “Silk,” too. This is the Bay Area headquarters of Bolt Threads, the fast-growing materials innovation company best known for making a synthetic spider silk, called Microsilk; it’s a fabric that’s been called “stronger than steel and more tear-resistant than Kevlar.” It’s spider silk, sans the spider.
“Spider silk is a much stronger natural fiber than traditional silkworm silk,” said Jamie Bainbridge, the vice president of product development at Bolt Threads. But aside from their strength, the two silks are very similar: smooth, lightweight, lustrous fibers that dye beautifully and have a natural resistance to water. The reason that traditional silkworm silk — more specifically, Bombyx silk — is so popular today is because it comes from a creature that can be domesticated, so it’s a readily available material. Silkworms can be farmed. You’ve probably never seen spider silk in a garment because it’s impossible to farm spiders. Under the conditions used to farm silkworms, spiders eat each other — which makes it near impossible to harvest spider silk naturally.
At the Bolt Threads headquarters, there aren’t any living spiders from what I can tell. Nor are there silkworms, despite the light fixture hanging in the conference room. Situated on the fourth floor of an inconspicuous brick building, the 32,000-square-foot facility feels like a small-scale labyrinth. It’s split into open-plan offices with diagonal ceiling lights, glass conference rooms that are named after fabrics like silk and tweed, and seven science labs that give off the nostalgic vibe of a high-school chemistry class, white lab coats and all. It’s here where funding and science collide, and man creates silk.
Making synthetic spider silk involves several simple ingredients and very meticulous science. Sugar, water, and yeast cells infused with spider DNA are combined and left to ferment in large stainless-steel tanks. The mixture is then centrifuged, purified into a powder and mixed with a solvent. The resulting liquid silk protein, which looks like glue, is in the same natural state as the liquid protein that actual spiders extrude from their silk glands and then form into fiber. Instead of using spiders, however, Bolt Threads has a system of devices that turn this silk protein into long continuous filaments of synthetic spider silk. Then comes the interesting part: figuring out what to make with this potentially revolutionary fiber.
Bolt Threads and synthetic spider silk have garnered some serious hype. The company, still in its infancy, has raised well over $200 million. In the past year, Bolt Threads bought Best Made Co., an artisanal outdoor-apparel company based in Brooklyn that is known for its sweaters, canvas bags and colorful custom axes. Bolt Threads has also partnered with high-end fashion designer Stella McCartney and outdoor juggernaut Patagonia. For all this hype, however, there’s been a surprising dearth of apparel made with synthetic spider silk. Stella McCartney created a one-off dress that was displayed at the Museum of Modern Art. Best Made Co. released a hundred winter beanies in 2017 that were 40 percent synthetic spider silk and sold for $198 each. And Bolt Threads itself sold a limited run of 50 neckties that were made of 100 percent Microsilk. They went for $314 a pop. The Patagonia collaboration has yet to bear fruit.
“We can design everything from the ground up and be more focused on the more sustainable, better-for-the-environment chemistries that you wouldn’t otherwise get in your standard textile processes. You get both performance and sustainability without sacrificing on either end.”
Part of the problem, frankly, has been that a great many things can go wrong when making synthetic silk proteins. It’s a fermentation process, not too dissimilar from making beer, and subtle changes in temperature, pH levels and the viscosity of the liquid protein can ruin the batch. And the risk of something going wrong increases, according to Dan Widmaier, cofounder and CEO at Bolt Threads, when you try to scale up the process to make larger quantities. The optimism for synthetic spider silk comes with the knowledge that once the process is perfected, all that’s needed to make larger quantities of silk is more fermentation tanks.
“The reason that biology is the manufacturing solution of the future is because you feed [the protein] sunlight or sugar, keep it roughly the right temperature, and, in our case, [add] yeast, and every four hours it doubles, ” Widmaier explained. “So you get twice as much material as you had before, and that works from a single cell to growing metric tons of cells.” The next step for Bolt Threads is acquiring larger vessels — that’s the way to move forward.
The biggest fermentation tank in its Bay Area facility is 200 liters, but Widmaier said the company has rented out larger facilities in the Midwest and Florida, and they can now make metric tons of synthetic spider-silk protein, meaning metric tons of apparel. (For reference, one metric ton of protein can make 6,500 shirts that weigh 150 grams each.) “We’ve had to learn how to methodically go about this process,” Widmaier said. “It’s expensive, hard, but potentially very rewarding in the capabilities of the product that we can deliver.”
For brands, the thing that’s appealing about synthetic spider silk, maybe just as much as its inherent properties like strength, stretch and softness, is that it’s a new material. And that’s because as of late, there’s been little innovation with materials in the apparel industry. Cotton, wool, polyester, nylon, spandex and Kevlar — all are more than 50 years old. So if you invent a new material, it’s going to drive interest simply because it’s new. In years past, having a material like Gore-Tex, Cordura or Lycra in your apparel made you different. It was a protectable and tangible benefit to the product that you were selling, but that’s largely gone away. Pretty much any brand on the planet can use those materials now.
Consumers want to know where synthetic spider silk fits in the greater landscape of apparel, and the truth is that Bolts Threads doesn’t know yet. Its best application could be underwear, outerwear or sewing silk. Widmaier said they’re hoping the apparel brands will figure it out. “We’ve learned that when you have new materials,” he explained, “what you really want to do is get smart people who make cool products, find where they work, and then they’ll figure out how to put specs around that.”
That’s not to say they haven’t tried to figure out its best application. Take Best Made Co.’s beanie for example. They found that it was significantly warmer than anticipated. They hadn’t accounted for the fact that spider silk naturally shrinks when contacted by water — Widmaier said it gets “plasticized.” So when dew forms on the web in the morning, causing it to sag, the fibers tighten up and the web naturally fixes itself. They didn’t originally account for this super-contraction with the beanie, which was made of Rambouillet wool with synthetic spider silk. “We did the measurements, and it turns out it was like thirty percent warmer than anything else,” Widmaier said. “It has nothing to do with the strength property, but for some parts of consumer apparel, there’s pretty good value in that. Same weight of fabric, much warmer.”
Bainbridge, whose focus is more on the yarn- and textile-development side, and Mitch Heinrich, who is the director of special projects at Bolt Threads, told me that the fabric made with synthetic spider silk can make existing products lighter. When a material has a high strength-to-weight ratio, like synthetic spider silk, it can drastically reduce the weight of a product like a jacket while keeping it strong and durable. It has inherent stretch characteristics, too, which furthers its versatility. It could, in theory, be used as an alternative to traditional fibers like lycra, spandex, nylon and polyester to make all kinds of things, like workout clothes. “We believe that we can get to somewhere in that performance range, but in a totally sustainable material.”
And that’s a big draw for synthetic spider silk — sustainability. The textile industry is a historically filthy industry — it’s actually the third largest polluter of water on Earth, according to Bainbridge — and one of the goals at Bolt Threads is to change that. Synthetic spider silk, because it’s just sugar, water and yeast, is completely biodegradable. It’s a huge reason why brands like Patagonia and Stella McCartney want to partner with Bolt Threads today.
This sustainability ethos was one of the reasons that Bolt Threads bought Best Made Co. in the summer of 2017. The Brooklyn-based company tells natural-materials stories, as Widmaier described it, but the acquisition made sense for other reasons, too. It sold premium products and — news flash — synthetic spider silk isn’t cheap. It was mainly direct-to-consumer, so it could sell these high-end products at more affordable costs. And, maybe most important, it provided a channel for Bolt Threads to tell its own story, while simultaneously working with the product- development team at Best Made Co. to figure out how to best use the fabric. “We need to demonstrate to both designers and consumers that there is a virtuous cycle here,” Widmaier said, “that we can invent new things that create new benefits, that enable new products, that then go out into the world. And Best Made is really a way to break the supply chain.”
Bolt Threads isn’t the only company making synthetic spider silk, though. Japanese company Spiber has partnered with The North Face and Goldwin, and has already integrated its synthetic spider-silk material in proof-of-concept winter jackets. In Germany, AMSilk partnered with Adidas to create a pair of synthetic-silk sneakers. What makes Bolt Threads different is that it’s focused exclusively on consumer soft goods. Other companies are making medical devices, industrial products and car parts in addition to apparel. That’s great, but Widmaier wants Bolt Threads to have a narrower focus on products that “touch the human body.”
The potential for synthetic spider silk is huge, as is the anticipation of what the partnerships with Stella McCartney and Patagonia will yield. “At Bolt Threads, they are fusing fashion, sustainability and technology, offering a solution that we are just beginning to explore the applications of,” said Claire Bergkamp, the head of sustainability and ethical trade at Stella McCartney. But when you talk to Breslauer and Widmaier, you realize these partnerships that revolve around synthetic spider silk are actually just the tip of the iceberg for Bolt Threads. Now that the company has refined the process and can produce synthetic spider silk at scale, it opens the door to producing other scaleable silk fabrics out of protein. For example, instead of spider silk, they can now create a protein that expresses the properties of a squid’s beak, one of the strongest materials in nature, or the wings of a dragonfly, one of nature’s most flexible materials.
Making fiber-forming proteins that have different mechanical properties, such as high tensile strength, elasticity, durability and softness — that’s what Bolt Threads is good at. “We can design everything from the ground up and be more focused on the more sustainable, better-for-the-environment chemistries that you wouldn’t otherwise get in your standard textile processes,” Breslauer said. “You get both performance and sustainability without sacrificing on either end.”
The interest in synthetic spider silk, up to this point, has been based on people being amazed at how strong it was. Yet it’s possible to create other silk fabrics that are even stronger, stretchier and maybe even lighter or warmer — it all depends what other natural materials are mimicked. “When we look at the world, we actually see a platform of properties — it’s not like we just make spider silk,” Widmaier said. “We’re going to make many materials capable of making lives better in many different ways.”
Speaking of more materials, Bolt Threads isn’t limiting itself to protein-based silks. In April 2018, the company announced its second new material, Mylo, which is a synthetic alternative to animal leather. It’s grown using mycelium, or the root network of mushrooms, so there’s no fermentation or yeast involved like there is with Microsilk. The mycelium spores are placed in corn stover, or the ground-up biowaste of corn (like its stalk), and the spores are allowed to grow into a network of small fibers that create a soft foam. This foam can then be sliced, cured and tanned. The end product looks, feels and has comparable properties to natural leather.
“It’s not like we just make spider silk. We’re going to make many materials capable of making lives better in many different ways.”
Mylo is a joint effort between Bolt Threads and Evocative, a company that’s been working with mycelium for decades to make an environmentally friendly alternative to styrofoam. Unlike the mycelium packaging that Evocative makes, Mylo is grown in carefully controlled conditions (humidity, temperature, CO2 and oxygen levels) so that it’s a much more refined material, perfect for consumer goods. Mylo theoretically could be used in any product that’s traditionally made of leather: wallets, keychains, bags, jackets, etc. Like natural leather, Mylo can be dyed and will patina over time. Bolt Threads will release a limited-edition handbag, made entirely of Mylo, this July. There’s also another collaboration with Stella McCartney in the works.
Just like with Microsilk, Mylo is a new material that’s made with renewable resources — which is Bolt Threads’ ultimate goal. “The vast majority of the company still works on Microsilk and where that’s headed,” said Widmaier. “I think what [Mylo] is really a statement that we’re about, which is better materials for a better world, and we’re going to look anywhere and everywhere that we think we can achieve that goal.”
The real win for Bolt Threads, according to Widmaier, will be if they’re able to create new materials, like Microsilk and Mylo, with varying properties and bring them to market each year. “If you can do things much quicker, then you worry less about how one material has to supplant everything,” he said, “and more about how we can make better materials for each of the applications that show up in your life: in the things you wear, the things you carry around, your shoes and your accessories — all of that.”
It took Bolt Threads nine years to get to where it is now, but the company is in a fantastically optimistic position. It could potentially make multiple new fabrics, at scale, every year for the foreseeable future, each with properties that could alter some aspect of apparel, whether in canvas bags, cotton shirts, synthetic down jackets, shoelaces or anything else. And there’s the potential to create more leathers, like Mylo, with different properties, although Widmaier admits it’s still too early to know exactly what those could be. It’s a remarkable thing to think about, considering that it’s been nearly 50 years since there was a new fabric. Now, in the space of few years, Bolt Threads has invented two, with the potential for many more in the near future. And it was all inspired by an insect you’d probably want to squash.
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