One of the draws of denim—arguably its main draw—is how it ages. No other fabric breaks in quite the same way, leaving a history of the wearer on its surface in faded indigo.

Levi’s and other denim manufacturers go to extraordinary lengths to give brand-new jeans this patina, recreating the wear patterns they find on vintage pairs. And one of their most valuable tools to do this is potassium permanganate. It’s an oxidizer, similar to bleach but with a shorter life that makes it easier to control and safer on fabric. It’s “used on almost every jean that’s processed in the world,” says Bart Sights, Levi’s vice president of technical innovation. Denim brands use it to lighten jeans and give them that perfectly broken-in look that has drawn generations of shoppers to denim.

The chemical has its drawbacks, however. It can irritate workers’ skin and lungs if they aren’t wearing their protective equipment, and can be harmful to aquatic life if it isn’t treated properly before being disposed. A couple years ago, when Levi’s started its Screened Chemistry program, to identify and eliminate undesirable chemicals from its supply chain, the first one it realized it needed to phase out was potassium permanganate. “We were like, ‘Oh boy,'” says Sights of the team’s reaction. It was so widely used and so critical to finishing denim that quitting it would present a serious challenge.

Oddly enough, trying to solve the chemical problem caused Levi’s to stumble upon a labor-saving technological innovation that is transforming the way it designs, makes, and sells its jeans. Its replacement for potassium permanganate has turned out to be powerful digital tools and lasers that let it create precisely worn-in jeans quicker than ever—in about 90 seconds to be exact. The new model, called Project F.L.X. for “future-led execution,” has cut the chemicals needed for finishing down from thousands to dozens, and will make Levi’s far faster and more flexible in how it delivers its products to market.

Levi’s is introducing its new innovation at its major factory partners across the world, says Liz O’Neill, the company’s chief supply chain officer. ”This is not just something we’re experimenting with and certain programs are going to be made this way,” she says. “We’re fully rolling this out.”

Lasers and Levi’s

To understand the scale of the change in how Levi’s makes its jeans, you have to first understand finishing. When the designers at Levi’s create a new pair of jeans, they sketch the body, deciding on the silhouette and details such as where the pockets will be. But they also develop a finish, which includes color fading to the indigo, as well as all the distressing and wear marks that make a pair of brand new Levi’s jeans look like they’ve been lived in for years.

“The finishing process is the most intense part of the design process for denim,” O’Neill says. Thirty years ago, there were three finishes: dark, medium, and light. Today, Levi’s offers more than 1,000 finishes each season, sourced from real wear patterns on vintage Levi’s or dreamed up by designers. They’re so much a part of what Levi’s does that the company considers them one of its competitive advantages.

To create a prototype involves back and forth discussions with designers and could take anywhere from two to five days, depending on the complexity of the “recipe.” Levi’s Eureka Lab, which Sights heads up, has to figure out how to impart all that whiskering and fading on a fresh pair of denim.

And then there’s a greater challenge: They have to work out with Levi’s supplier factories how to mass-produce several thousand pairs, keeping the look and quality as consistent as possible across all of them. Traditionally, Levi’s might sponge or spray on chemicals, such as potassium permanganate, to lighten certain areas, and manually distress them with sandpaper, using dremel tools to create holes. At a Levi’s supplier in, say, Mexico or Turkey, the result is a room full of workers doing the “dry processing” jobs of manually hand-sanding or distressing jeans one by one, based on a sample pair hanging in front of them. On average, a worker makes two to three pairs per hour.

Now, in roughly 90 seconds, a laser does the same job, and does it exactly the same each time.

What it’s actually doing is burning away a very fine layer of cotton and indigo, much as a layer wears off through rubbing during regular washing and wear over time, or when sanded by hand. When the laser is in action, the jeans smoke. “If you want a hole in it, it’s actually going to catch on fire,” O’Neill says. They have to wash the jeans after to clean off the thin layer of ash left over, but they use the opportunity to apply any tint they want, if they’d like to give the color a greenish or brownish cast for instance.

The designers no longer need to spend days going back and forth with physical prototypes. They design everything digitally, using tools Levi’s developed itself to allow them to work with photo-realistic samples of jeans that don’t physically exist yet. The digital file contains instructions for the lasers, so there’s no longer any need to worry about how to replicate the look in mass production.

The change has cut development time for a new pair of jeans in half. “In the past, when a recipe might be 15 to 20 different steps of manual and machine applications, now all of our recipes are three steps,” Sights says, “one of those being a laser.”

How Levi’s stumbled into its big innovation

All of this came about because of potassium permanganate, or rather Sights’ and the team’s efforts to get rid of it. “Laser was an alternative. It’s not a chemical. It’s safe to use,” Sights explains. “But we couldn’t get it as white as permanganate, and then sort of by accident we saw that you could get it as white as permanganate if you did it on a garment that was already washed.”

That realization set off a chain reaction that led to what Sights describes as their “radical breakthrough” with Project F.L.X. Sights, O’Neill, and the others involved understood right away that if you can keep a stock of jeans in different washes available that you can finish quickly with lasers, you don’t have to decide which finish they’ll have until much later. The business benefits of that simple shift are huge.

Normally, Levi’s would have had to choose the finish on a pair of jeans right at the start, since they were time-consuming to create. The lead times to produce a style, from concept to market, could be more than six months, meaning Levi’s was forced to guess ahead of time what shoppers would buy, then invest time and money to produce all the jeans up front. If they didn’t sell, Levi’s would discount them, eating into its margins. And if a style was selling well, Levi’s couldn’t quickly restock it.

Under its new operating model, Levi’s says lead times can shrink to weeks, or in some cases just days, giving it the flexibility to see what shoppers are buying first, and then finishing inventory to match. At its partner factories, it plans to keep a stock of anywhere from three to five base washes, depending on the fabric, for each style of jean the factory makes. The factories can do the finishing with lasers as needed.

Levi’s expects the change to dramatically mitigate the problems of inaccurate trends forecasting, and keep margins fat. A similarly agile, responsive supply chain is a key part of Zara’s astounding success, and a goal that leading brands such as Nike and Adidas are actively chasing to improve their operations.

Levi’s has already built a giant finishing facility in the basement of its Sky Harbor distribution center outside of Las Vegas. “We can stock 511s in our distribution center and literally as we get new orders or as we’re chasing products or filling in sizes, we can send those base washes down to the laser area and actually have them in and out, fully finished, and boxed and ready to go, within six hours,” O’Neill says.

To make their idea into reality took more than just deciding to use existing technology in a new way. Though denim makers have been working with lasers for about 15 years, typically they would just use them to start a wear or distress pattern on a pair of jeans. “The laser process just didn’t look quite natural,” O’Neill explains. At Levi’s factories, it still took human hands to smooth it out and make it look right. (Some Japanese factories, it’s worth noting, were already using similar technology to finish denim entirely with lasers.)

Levi’s says the digital imaging software it had access to was also less than ideal. It provided what looked like a cartoonish, graphic representation of jeans, not a detailed digital replica.

So Levi’s built new tools itself, working with its partner, Jeanologia, a Spanish firm that makes lasers and other products for denim finishing. For the last 18 months Levi’s has worked to create a digital platform that lets its designers see and manipulate wear patterns and distressing on a photo-quality representation of a garment. The digital jeans look much like a high-resolution product image you might see at an online retailer, except with these, they can change them any way they like, and then send instructions electronically to a laser to create them.

The rollout and its impacts

If you’re looking to get a pair of jeans finished entirely with lasers, you won’t be able to find them on the market just yet. The company says it will roll out the new digital platform over time, and expects to have it fully scaled in 2020.

Levi’s has already been testing the process at its own factories, though. (It owns two: one in Poland and one in South Africa.) It’s also working with its major partners right now to get their operations ready. Of Levi’s many suppliers (pdf), about 20 form the core the group responsible for making most of the brand’s jeans. Most already had lasers but they weren’t using them this way. Sights says the factories will have to increase their investment in lasers as Levi’s scales the new operating model.

The workers at these factories are sure to feel the change, too, and there will be fewer jobs for humans. ”It’s not just a one-to-one transition from the hand-sanding to the lasers. You aren’t going to need as many people,” O’Neill admits. But she said she doesn’t anticipate layoffs because “there are plenty of other places in the factory for anyone who wishes to stay to actually get retrained.”

Manual finishing, part of the dry processing stage in a factory laundry, is just one role among many. There are jobs managing materials, cutting fabric, sewing, working in the laundry, and packing and shipping. Hand-finishing is also a highly repetitive and physically demanding task, and Sights says it’s not a great job to begin with.

O’Neill adds that there’s a lot of turnover and moving around to new jobs in apparel factories, too. “This is very common in the factory setting,” she says. “As processes change, especially in the laundry, there’s sort of a constant retraining and repurposing of the workforce.”

At the Eureka Lab in San Francisco and at the Sky Harbor facility, the company has already had success quickly retraining workers to use the lasers, so they’re optimistic the transition will be relatively smooth in their supplier factories too.

Authenticity, brought to you by technology

A digitally produced wear pattern replicated thousands of times over by a machine might seem somehow distant from the folksy appeal of broken-in denim. Denim purists who buy their jeans raw and wear them to get fades as unique to them as a fingerprint might not love Levi’s new laser process (though plenty of denim obsessives buy pre-distressed jeans too).

But Sights and O’Neill insist that designing digitally and finishing jeans with lasers won’t have an affect on the authenticity of Levi’s products. If Levi’s was already artificially distressing jeans in a production line, then what’s the difference?

“Designers are still fully obsessed with the heritage and authenticity of Levi’s, and all of this protects quality of our product as well,” O’Neill says. “We’re just really transitioning our designers from a physical iteration to a much more modern, digital way of doing that development stuff, which is actually far more efficient and far faster.”

Sights remains fixated on preserving what makes worn denim feel so special. He says even the lighter base shades start dark, and the company still washes them to slowly rinse out the dye, rather than just making them in a lighter-colored fabric. “The beautiful thing that we like about jeans, whether we realize it or not, is the contrast in the seams,” he explains.

“What we love about denim, whether we realize it or not, is all the high-lows, the ropiness of the seams, the texture,” he says. “The thing that we’ve gone all-in on now is we’ve placed on ourselves the constraint that we will drive all these different finish attributes only with the laser file. That led us to the need for a tool, and as Liz said, there’s a lot of digital tools out there but none of them look like this on denim.”

Levi’s feels it has solved that problem. The company that made its name as the creator of the first modern blue jean, the original outfitter of miners, cowboys, and rebels, will be blending the past and present in every pair of laser-etched denim.

This story has been updated to reflect that Japanese companies had previously used similar laser technology to Levi’s.