I don't know how many versions Mies van der Rohe discarded before he was satisfied with his Barcelona chair or how many Poangs-in-training Ikea had before it settled on its classic, but woodworker Robert Erickson is on the 60th version of a chair now called the Niobrara Office Chair.

Erickson, a Californian who is in the Twin Cities through Sunday, April 13 at the American Craft Council show in St. Paul, custom makes the office chairs to fit more than a dozen personalized measurements. Friday through Sunday at 1:15 p.m., Erickson and his son Tor demonstrate how each chair is customized to a person's back, legs, seat and height.

More than 60 hours of labor are required by the Eriksons to craft each bentwood chair, plus nearly a dozen hours by the upholsterer and harvesting and drying the materials. The flexible slats that rest against a person's lumbar region are flexible, allowing more comfort.

Erickson's Niobrara chair, named after a river in Nebraska where Erickson grew up, is a melding of sustainable black walnut from California and leather from free-range Great Plains bison.

The chair is in its current form has been sold since February after it debuted in Baltimore. Three have been sold so far for $5,800 each. Expensive yes, but it's not a delicate piece of art. "It's extremely durable and very well-made," he said. "Ergonomists, dcotors and chiropractors love it."

Erickson will be able to custom fit the chair through Sunday. After that, fittings are done at Grand Hand gallery in St. Paul.

Tickets to show at RiverCentre in St. Paul (199 Kellogg Blvd. W.) are $11. Friday night only, tickets are $5 on site after 5 p.m.