Springfield Twp.: Raku is art in extreme form.

The pottery firing process is a fireworks show in miniature, producing a display of sparks and flame and resulting in a finish that’s distinctively irregular.

Ceramic artist Jack Valentine specializes in American-style raku, and every year he opens his studio on Pickle Road to let people experience the process. That opportunity is coming around again during his annual open house, which starts Friday afternoon and continues until Sept. 28.

The open house is a small-scale art show, with Valentine and six other artists displaying and selling their work. But it’s also a chance to participate in the magic that turns a clay vessel into an object of beauty.

I got that opportunity a few weeks ago, when I watched Valentine fire a few raku pots in a handmade kiln in his garage.

The art form, I discovered, is not for the timid.

Valentine’s propane-powered kiln reaches almost 2,000 degrees Fahrenheit, fiery enough to make the pots inside glow orange-red. A small opening in the side of the kiln lets you peek into this miniature Hades as the glaze that covers the pots turns from a paint-like substance to a glassy coating.

Valentine’s kiln is heated with a propane-fueled burner that shoots a jet of flame into an opening near the kiln’s base. It takes about 45 minutes for the heat to bake the clay and liquefy the glaze.

Timing is critical. Valentine fires by sight, stopping the firing process when the pots achieve the shiny, smooth appearance that indicates the glaze has melted.

If he leaves the pots in the kiln too long, he’ll ruin them. “You can overfire in a matter of five minutes,” he said.

Then the fun starts.

Wearing heavy gloves and sunglasses to protect his eyes from smoke, he turns off the burner, removes the top of the kiln and uses large tongs to lift out the pots. That’s what makes raku different from other firing processes, Valentine said: It’s the only one that involves opening the kiln and removing the pots while they’re still extremely hot.

The thermal shock of the blazing hot pots hitting the cooler air causes the glaze to crackle, giving raku pottery its distinctive crazing. The cooler the air, the more the glaze will crackle, Valentine said.

He sets the pots atop a bed of sawdust in 50-gallon steel drum that’s been cut in half lengthwise and hinged. The sawdust sparks and flames, ignited by the pots’ intense heat. There’s an element of danger to the operation, an excitement that comes with creating art on the edge.

“I’m known to lose eyebrows,” Valentine said, “and I’ve lost a goatee or two.”

His fiancee, art historian Stefanie Hilles, pours more sawdust atop the pots in a smothering process called reduction. The process reduces the pots’ contact with the air, drawing oxygen out of the clay body and pulling carbon in, explained Suzi Nolt-John, a fellow ceramic artist who was working with Valentine on the day I visited.

The carbon creates a satiny black finish wherever the pot is left unglazed, Nolt-John said. The reduction process also causes copper in the glaze to take on a metallic gleam, although the extent to which that happens is a bit of a crapshoot. Factors such as the outside temperature and atmospheric pressure can affect the finished appearance of the glaze, she said.

The closed barrel then sits for another 45 minutes or so, belching occasional puffs of smoke. Now and then Valentine will open the barrel to flip the pots with his gloved hands and speed their cooling.

Once the pots are cool enough to handle, they’re placed in the shade to finish cooling, which takes about 20 more minutes, Valentine said. Then they’re scrubbed with steel wool and pumice soap to clean off the ashy residue and reveal their beauty.

Participants in the open-house classes get to glaze their own pots using a small selection of commercial glazes. “Lots of little kids come. … It’s just painting,” he said.

Just painting, with a bit of pyrotechnics.

Mary Beth Breckenridge can be reached at 330-996-3756 or mbrecken@thebeaconjournal.com. You can also become a fan on Facebook at www.facebook.com/MBBreckABJ, follow her on Twitter @MBBreckABJ and read her blog at www.ohio.com/blogs/mary-beth.