On a recent afternoon, chef Vikram Garg is bent over his clay pot tandoor, seasoning the oven. He holds a kitchen towel that has been twisted into the kind of whip commonly used in middle school locker rooms. It's dripping green globs. With a practiced hand, he twirls it inside his tandoor until every inch of the surface is covered.

After a few hours of drying time, he will fire up the modern, gas-fueled tandoor to low heat and start a three-day curing process to prepare the oven for baking.

IndeBleu executive chef Vikram Garg demonstrates the seasoning technique he uses on his tandoor ovens. (Bill O'leary -- The Washington Post)

At the hot, new Indian-inspired French restaurant, IndeBleu, chefs bake more than 1,000 pieces of bread on a busy night for Naan Provencal. That's executive chef Garg's leavened flat bread topped with fresh, chopped herbs and crunchy sea salt. But this volume of baking is tough on a tandoor. So Garg makes sure his is in shape by applying a traditional vegetable-based seasoning, a sort of do-it-yourself Teflon, to the interior wall.

"That's what master chefs in New Delhi taught me to do," says Garg. But he admits that his teachers "could not explain the science." The goal is an oven surface that will hold the raw dough in place but not allow the finished bread to stick and ultimately burn.

His seasoning recipe is simple. Into a blender go two handfuls of spinach leaves and one cup of coarse kosher salt. "Each ingredient has a different role. The spinach acts as a binder, and the salt gives flavor to the bread," says Garg, 35, who calls his cooking "contemporary French accented with flavors of India."

A cup of buttermilk is added next. "It's for lactic acid," he says. The addition of one cup of pungent mustard oil and one cup of jaggery -- an unrefined sweetener made from sugar cane -- is meant to glaze the interior of the oven. The resulting stiff liquid, which he pours from blender to bowl, looks like an Indian version of pesto.

For centuries, cooks of the eastern Mediterranean and central plains of Asia and beyond have baked leavened flat breads in clay-pot ovens. The tandoor, a baking and roasting oven essential in India and Pakistan, is one example, and over the years breadmakers have developed pastes to season their clay ovens to produce perfect flat breads.

The tandoor principle is simple. A charcoal fire is built in the bottom of the vessel. The ensuing, wrap-around high heat is regulated by opening and closing a vent at the bottom in conjunction with a lid at the top that covers a wide mouth.

At mealtime, wads of dough are smacked against the interior sides of the oven where they quickly balloon and bake while taking on a light, smoky flavor. (Long, steel skewers of marinated meats and vegetables can be tandoori-roasted at the same time.) But getting the dough to stick to the clay walls and removing the finished bread, such as delicious, chewy naan, can sometimes be harder than it looks.

Tandoors vary. A baker needs to know where one was made. Clay pots differ in composition from region to region. Tandoors made in the western part of India, for example, are kiln-dried, while the tandoors of the north dry naturally in the sun. Some have a smooth interior wall, while others are rough to the touch.

One oven might benefit from a one-time or periodic seasoning procedure while another won't require it.

"Everybody has a different style of seasoning, if they season at all. It's their personal choice," says Achal Jain, owner of Nishi Enterprise, an importer of tandoor ovens based in Linden, N.J. "They can make a simple paste, commonly with yogurt and eggs, or they go all the way with many different things."

In the Washington area, some take a minimalist approach.

When the dough won't stick, Balraj Bhasin, owner of Bombay Curry Co. in Alexandria, rubs the inside of the tandoor with salted water. "In my personal opinion, you don't need to do more," says Bhasin.

At Naan & Beyond, a tandoori carryout in downtown Washington, chef Waheed Muald is firmly against any seasoning regime. "No egg. No salt. No ground chickpeas. No nothing," says Muald, who is noted for his flavorful tandoori lamb.

But most chefs we contacted make a curing paste with a minimum of sugar, spinach and mustard oil.

IndeBleu's two, gas-fueled tandoor ovens are a far cry from simple. Waist-high, they are clay pots encased in stainless steel cubes, insulated with sand. Garg seasons them about every two months.

Garg says the first breads made after curing the oven are darker than they should be and taste strongly of mustard oil. "We eat those in the kitchen," says Garg. "But then it's ready, and we can serve breads to our guests."

The curing process is a lot of work, but Garg thinks he has it easy. "In ancient days there were no blenders," he said. "The people had to do all this with a mortar and pestle."