"When the hot metal catches them, they explode into these huge fire balls and float off into the air and give off these loud, horrific booms."

Artist Heather Powell is talking about the oxyacetylene-filled balloons that will be ignited during the closing reception for "Wear and Tear," her exhibition at UnSmoke Systems in Braddock. The free public event will take place from 7 to 9 p.m. Saturday.

The performance segment will also "probably include gunpowder. We'll take advantage of the fact that we're working with fire, and we'll pour molten iron into things, like ice."

That's fine for her. She's used to tipping 80-pound ladles of molten metal to make her artwork. The evening will also include an iron pour that will demonstrate standard and alternative ways of creating sculpture, and a community potluck.

Celebrants are encouraged to bring something -- bread or a pizza for example -- to bake in the large, wood-fueled outdoor oven built by Ray Werner's Pittsburgh Community Brick Oven Project. Local restaurants will provide beverages.

Organizers hadn't planned to fire the oven at the exhibition opening last week, but they did because people showed up with food to bake.

"It's really beautifully made, and it makes great pizza," Powell says.

People can bring pizza topping ingredients, or another potluck dish, if they don't have anything for the oven.

Inside the renovated Catholic school that has become one of the city's hottest new alternative art spaces, Powell and Gavin Kenyon exhibit drawing, installation and 26 mixed-media sculptures, including pieces made of cast iron, the material that will feed the evening's pour.

The iron pour will be a collaboration between Powell and Kenyon, and Ed and Carley Parrish of Hot Metal Happenings. The artists are part of a growing Pittsburgh community of people interested in doing cast-iron work, themselves part of a larger population scattered about the country, who were inspired by Ken Payne.

They refer to Payne, a member of the art faculty at Buffalo State College in New York, as "the grandfather of the movement in this region," Powell says.

Powell and Kenyon met while attending the School of Visual Arts in New York City, and moved to Pittsburgh about three years ago. She's a native of Hickory, Washington County, and he hails from near Ithaca, N.Y. The core local hot metal group comprises about eight artists, and periodically expands by four to seven more people.

They built a furnace in the UnSmoke gallery parking lot for this event, which will illustrate the process of iron casting, beginning with the metal entering the molds and ending with breaking them apart to reveal finished artworks.

Powell says they've gotten fairly fast at assembling furnaces, having done so for demonstrations at other locations such as the Braddock docks and the Manchester Craftsmen's Guild, where she is curator of exhibitions and related programming.

The furnace is about 51/2 feet high and its ladle will hold 50 pounds of molten metal. Furnaces are made of discarded materials, and this one was once the exhaust for an industrial bead-blasting cabinet.

"Everything we use is recycled," Powell says, "the equipment, the furnace, the metal," and that green component is part of the appeal for the artists. People frequently call one of them when they have something to donate. Radiators are the most abundant item, Powell says, but they also receive a lot of "ornate architectural elements. Anything cast iron."

Casting in a sand mold is most typical, but other methods will be tried. One artist plans to work with cardboard and wax, and Powell will cast molten iron through a magnetic field to produce small geometric forms that become magnetized as the metal cools.

The artists dress in leather and wear eye protection for the pours, and tape will mark off an audience safety zone. But there will be extra gear for visitors who want a closer look. "We can suit them up and walk them through the process," Powell says.

She recalls her own introduction to this hazardous artistic process.

"It all seemed very intimidating to me at first. But once you do it, there's no going back," Powell says.

She says their furnaces are much like blast furnaces, on a mini-scale, and in that way their process relates to the region's history.

"We feed the furnace with coke, alternating charges of coke with the broken up chunks of iron, 'til we get a full furnace. The iron melts down through layers of coke and collects in a well at the bottom."

In much the same way that artisans and craftsmen in the last century adapted the production of clay and glass from factory to studio, these artists have harnessed iron. That makes them a particularly appropriate group to set up shop in Western Pennsylvania.

"Wear and Tear" will be at 1137 Braddock Ave., Braddock. For information, visit www.unsmokeartspace.com.