"I like clay because it's forgiving," says porcelain potter Mary Briggs. "It reponds to your touch and changes as your ideas change."

The clay that Briggs molds, shapes and changes has responded to her maturing ideas since her early days as a potter at the Carnegie Institute. Her growth as a potter is evident in the works she has on display and in progress at her Arlington studio.

She brings out a coffee mug, completed five years ago, and one she finished recently."The old mug is technically pretty good -- the walls have a uniform thickness, the handle is firmly attached, the glaze is adequately applied. But there is is little attention paid to its form," she says.

"(Now) what I labor over is the form and feel a work gives."

The newer mug, she points out, "grows outward from a definite, grooved base. The shape of the handle complements the form of the mug, the walls are decorated, even the glazing is more elaborate. All of these elements make this a very special mug."

Could she do a series of nearly identical mugs? "Oh, no," she declares firmly, "I'll never be a 'production' potter. I'd rather make five fine pots and sell them for $30 and than make 30 pots for $5 each."

Even production potters such as stonewear specialist Cathy Brosius will tell you they make no two pieces alike.

"I would go bananas if I kept turning out the same thing," says this profilic potter, who works out of the Arlington house where she grew up.

Even her standard items -- fluted bowls, "peanut bags," woven clay baskets -- are deliverately different in form or glaze. Some of the differences happen by accident, as when her cat walked across one of the fluted bowls and left a paw print. Once, a moth got caught in a bowl, leaving "his ash and a beautiful impression."

The "peanut bag" -- and idea that stormed her brain "before Jimmy Carter ever got to office" -- are different in size and the way they sag. To create these clay counterparts to cloth, Brosius rolls out a slab of clay across a piece of burlap for texture and cuts different-sized rectangles. She folds these over, pinching together the sides and knocking them on their flattened bases to create a sagging effect.

With kilns and wheels costing hundreds of dollars, the artisans must rely heavily on shows and store sales to "feed the habit," as Briggs put it.

"But you can make good pots out of anything -- a piece of mud pulled out of the ground -- and you don't need sophisticated equipment to make your work succeed."

Sophisticated equipment widens a potter's range. Briggs works chiefly in porcelain because her kiln, an electric model, creates a "shiny, pretty effect on porcelain clay."

Brosius owns a gas kiln and pit for firing, as well as two electric kilns. The chemical difference this can make in the glazes, she explains, is monumental.

The electric kiln is clean-burning and fires by oxidation. But in the gas kiln, I can turn the fuel to the point where not enough oxygen is left in the atmosphere for the fuel to burn. So it attacks the oxygen in the glaze itself, which changes its (the glaze's) color." Thus copper, which turns a brilliant turquoise under the oxidation process, fires blood-red in a gas klin.

"I'm not a chemist, so a lot of the glazing I do is by trial and error," says Brosius. "It's fun when you produce a really unusual effect, but then it's hard to reproduce it."

Briggs backs this up. "Glazing is 10 percent material and 90 percent in how you do it. That's what makes it an art."

Both potters enjoy another glazing effect, acheived by throwing salt into a heated kiln. This gives the pots a metallic, spotted appearance. "Of course," says Briggs, "you can't do salt glazing in the middle of Arlington -- the pollution is terrific."

They both learned this method in courses at Penland, a North Carolina crafts school in which students spend studio time -- sometimes 14 hours a day -- with a resident artist.

"That was a fantastic experience," Brosius says of her two summers there, "but of course so much of the learning process happens after you come home.""

It was after Brosius' first summer at Penland and first experience co-teaching pottery with Briggs through the Arlington Recreation Department that she decided to quit her job as a Department of Justice computer programer and become a full-time potter.

Brosius belongs to nearly every craft organization in the Washington area, including one she and Briggs started two years ago, the Arlington Crafts Guild. Through these and other groups she enters shows, displays her work at fairs and sells to various craft stores and outlets here and on the Eastern Shore.

"The satisfaction you get from potting is from pleasing yourself," says Briggs. "If the pots are intellectually appealing to you, then you have succeeded.