– As fresh businesses inhabit long-vacant buildings in Detroit, an art once teetering on obscurity is increasingly used to set them apart.

"It's a craft that for many years ruled the roost," said Doc Guthrie, 73. "It started to go away at the advent of the computer."

Guthrie is a sign painter. His courses at a Los Angeles trade school impart the essence of original pieces using a hand and paintbrush, and they're increasingly sought-after — including by a couple of University of Michigan graduates who have since returned to Detroit to ply their new craft.

Kelly Golden, 28, and Jordan Zielke, 29, went full time with their Golden Sign Company in 2013. They have since created elegant, hand-painted works for many of the city's new storefronts and beyond.

The duo paint everything by hand. They don't have any employees, and their studio is in one of their apartment's rooms. Most of their marketing is through pictures they take of their work and post on Tumblr and Instagram.

"We were cold-calling and hitting the streets, handing out business cards at the beginning," Golden said, but now, "the phone's been ringing."

The owners of newly opened storefront businesses like the company's original, authentic approach to sign-making. It's a throwback, a nod to Detroit's legacy of handmade signs.

But it's also akin to the farm-to-table movement and the boom in locally made craft beers.

"There is a technological backlash and a turn to the more do-it-yourself in craft, in arts," Guthrie said.

The process for creating an artisanal sign usually begins with a rough pencil sketch. They consult with the client and come to an agreement on what it will look like. Then the image is either hand drawn or created through computer programs.

The pattern is made to scale on butcher paper. A machine is used to perforate along the lines, and they take the pattern to the work site. A bag of chalk is run along the perforations, creating a dotted line on the wall, window or other sign location. Then the image is painted using oil-based paint and brushes made of hog hair or squirrel hair, depending on the surface.

It was a process widely used during the mid-20th century. Faded, vintage signs are easy to spot in Detroit, although some brighter ones recently have been revealed as blight is knocked out.

Guthrie said the decline came as technology made it cheaper and easier for businesses to use vinyl or digital signs.

"And it all became homogeneous," he said. "Simple and boring."

The sign makers diminished. Guthrie, now in his 22nd year of teaching the craft, was lucky to have 25 students.

These days, he has 70 students and a waiting list at Los Angeles Trade Technical College. They come from across the U.S. and as far as South Korea and Australia.

"They remind us of who we were at that age," Guthrie said. "We're just weird people who love art, who love lettering, who love signs."

"Businesses are saying, 'I don't want that generic look — that stick-on look. I want that real look,' " he said.

Carhartt's Brian Bennett tracked down Golden Sign after seeing its work on Instagram.

"They're expensive, but they're worth what you pay for them," he said. "If you look at doing vinyl, it's more than twice [the price] to hand-paint it."

Their work included not just the Carhartt insignia, but a 55-foot-by-200-foot mural painted last August on the north side of the Detroit Carhartt, facing Interstate 94. The image of workers in Carhartt gear was inspired by Diego Rivera's Detroit Industry Murals, a highlight of any visit to the nearby Detroit Institute of Arts.

The project was a collaboration that also included Detroit-based illustrators James Noellert and Mike Burdick, he said.

Zielke said it took about 350 hours over 18 days as they worked to meet the deadline of the business' opening day after slowdowns with permitting.

"The Carhartt one is by far the biggest, most massive thing we've ever done, and that's just so cool to drive by it on the freeway," Zielke said.

Bennett said the couple's dedication is remarkable; they were humble and had an "extraordinary" work ethic.

"I just loved their chemistry," he said.

The two have been friends more than 10 years, and they have been dating about six years. They met in 2005 while attending the University of Michigan School of Art and Design in Ann Arbor.

"She sat right across from me in class," Zielke said. "Directly across from me, and I think we just struck up a conversation and became good friends."

After graduating they moved to Detroit.

"You get out of art school, and you're like, 'Ooh, what now?' " Golden said, adding that they sought to "make money doing something that we love."

Nick Tobier, associate professor at University of Michigan's School of Art and Design, previously had the two as students. He said their work is genuine, with reverence for tradition but not limited by it.

"They were, I would say, like the two people in the world I knew would always be artists," he said. "There's never been anybody like them before or since."