Now, they entrust the living culture to no one. It comes along on holidays, like a fifth child, and they bring a bag of flour to feed it. This stuff is called starter: it's a naturally fermenting mixture of flour and water which captures the wild yeast in the air. Each day, it is fed with up to eight kilograms each of flour and water, rises to the top of the tub, and is used, with a little left behind, which is then fed so it rises again, and so on.

The Pearts use it instead of yeast in their sourdough bread - once it bubbles right up to the top of the tub, it is mixed with dough plus more water, with liquid malt (made from barley seeds, which are germinated, then dried, crushed and turned into liquid) to give a bit of sugar and better caramelisation and flavour, and some salt.

By starter standards, the Pearts' batch is a bouncing baby, a mere infant. According to the two bread enthusiasts, in France one can find 100-year-old starter; in Egypt, there's 2000-year-old starter.

This is the type of information you can easily get out of Shane Peart, a self-confessed bread nerd, so much so that he renamed his business, formerly That Bagel Place in Isaacs, ''Bread Nerds''. It's a great name: it implies a dorky kind of obsession with bread, a lot of book smarts and a high level of devotion.

Bread Nerds has a smart cafe and a cavernous production space, where they make bagels, pastries, pies, and other baked goods. It's all out in Hume, on a street so new last year's street directory doesn't list it.

The cafe is so sleek, with creations so tempting, the lunchtime coffee crowd would go wild if it were, say, in the city or Manuka. The bakery, one of the largest private bakeries in Canberra, is where the magic happens. Each week, they make 10,000 or more bagels and 2000 to 3000 loaves of sourdough, among other products.

The oven, which can accommodate 220 loaves at a time, was a $4000 purchase on eBay from a seller in Sydney who had gone bust. The ''prover'', a coolroom set at two degrees, houses a batch of bagels getting a good three-hour rest. There's also a large pie cooker that can accommodate something like 40kg of meat at a time for the fillings: diced topside steaks for the beef pies or diced chicken for the butter chicken or chicken mornay pies.

Bread Nerds' products are sold around Canberra: at the Kingston Markets where the Pearts got started, the Exhibition Park and Southside farmers markets, many IGAs, markets of Fyshwick and Belconnen, and cafes such as Ona in Manuka.

Demand is such that the Bread Nerds business is understaffed. And Shane Peart won't hire just anyone. Employees must show the level of devotion to artisan breads that he has. He once interviewed a pastry chef from New Zealand and the two of them sat at a dining table for four days, talking about bread. Peart's teenage son dubbed them bread nerds. The name for the business in its new incarnation was born.

The story of the Pearts and bread starts in the early 1990s with a trip to New York. The couple came back with a hankering for American-style bagels, but couldn't find them here. Shane Peart's solution was to turn his back on his career at the Australian Security Intelligence Organisation and leap into baking. No training? No problem. He taught himself how to make bread by reading extensively and watching internet videos of people making bread. Only now that he is quite established is he getting formal schooling through the Canberra Institute of Technology.

Peart is, in every way, a self-made man who built his new life on the basis of mighty fine dough. His wife was surprisingly chilled out about her husband's drastic career switch: from the stability (and salary) of a human-resources role at ASIO to the uncertainty and unappealing hours of a baking business. Her man was equipped only with his considerable passion.

Sharon Peart admits, ''It was a bit scary because we had three children at home and a mortgage. I said just go for it. I'm at home doing what I want to be doing, raising the children, he needs to do what he's happy doing as well. We thought, worst comes to worst, we lose the house and move on.''

Peart hit rock bottom on his first day of business. He was reduced to tears when, having worked 20 of the previous 24 hours, sales for the day amounted to just $64. He says, ''I sat down and cried for 10 minutes. I was sitting there thinking, 'What have I done?' Now I think, 'You've done it, all you have to do is keep going.' ''

It looks good now. You might say there's no business like dough business. Their four children (17, 15, 12 and 7), heirs and heiresses to the bread empire, enjoy the fruits of their parents' labour. They have excellent school lunches.

Sharon Peart says, ''And they're so spoiled, they're like, 'We don't want pastries today.' ''

Her husband adds, ''[They say], 'We're sick of danishes, Dad, can we just have tiny teddies?' ''

The Pearts are fervent in their devotion to good bread. Inferior offerings at some restaurants infuriate them. ''It drives us crazy. We're going out to dinner at fine dining restaurants in Canberra and find supermarket breads and packet focaccias,'' Sharon Peart says. ''Tastes have matured. Really, [customers] don't want packet bread. They expect good food.''

Shane Peart uses only natural ingredients. If he must use a preservative, he uses vinegar. His disdain of chemical mould inhibitors is palpable. He is a purist. A kind of bread savant. Like wine connoisseurs who can take a sip and say which vintage it is and what variety, he can munch on restaurant bread and identify the bakery that made it.

If his dreams keep coming true, Canberra will see much more of Bread Nerd's offerings around town, fulfilling his ambition to build two or three little outlets around the city.

Claire Low is a staff feature writer.