A tour of Calgary's Big Rock Brewery is sure to delight both the mind and the taste buds

It's early afternoon on a Wednesday, and four Calgary retirees aren't taking it easy. They're traipsing past grist mills and industrial tanks on a tour led by Alan Foster, a fellow pensioner who spends three afternoons a week sharing his passion for beer, and the beer-making process.

The tour group -- four residents of Manor Village at Garrison Woods, their two aides and a pair of beer-loving young men -- find an amicable guide in Foster. As one struggles to make it up an industrial catwalk, he chuckles with understanding.

"It's nice to have someone on the tour as old as I am," he says.

Big Rock Brewery was founded in 1985 by Ed McNally, a farmer/entrepreneur/lawyer who owned land near the Big Rock, a 15,000-tonne glacial erratic southwest of Calgary. In the 23 years since its inception the company has grown to be one of the biggest independent breweries in Canada, and today ships beer from Vancouver to the Maritimes.

The brewery has run private tours since their inception, and started the public tour in 1996. The groups in general range in age from 20 to 50; the only constant is that each guest is over 18, the legal drinking age in Alberta. The hour-long tour costs $20, and at the end, visitors can fill a 6-bottle take-home pack with their favourite brews. Foster, who has worked for both Big Rock and the Alberta Liquor Control Board, has been a guide since his retirement in 1993.

"There's no restrictions on pictures," says Foster, clad in a plaid shirt, suspenders and baseball cap. "Just none of me."

Station 1: Ingredients
The first stop on Foster's tour of Big Rock Brewery, located on 14 acres of land in eastern Calgary, are the stores of raw ingredients: wheat, hops, yeast and malted barley. According to the Reinheitsgebot (also known as the German Beer Purity Law) of 1516, beer should have only three ingredients: water, barley and hops. The law was amended in 1987 to include additional ingredients, and with a few exceptions (such as their Honey Brown Lager), Big Rock adheres to this voluntary directive.

Station 2: Mashing
To convert the raw ingredients into beer, the malted barley is cracked in a mill and then mixed with heated water; complex sugars start to break down, converting the mush into a sweet liquid called wort. Foster leads the tour to mammoth metal tanks filled with the viscous substance, which is heated up to 75°C and, as he observes, "looks like a big bowl of porridge."

Station 3: Brewing
The mash is pumped over to a second tank and boiled. Hops are then added, giving the mixture a bitter taste to balance the sweetness of the wort. The exact amount of hops varies from beer to beer, and according to Foster, is the secret of brewmaster Paul Gautreau.

Station 4: Fermentation
Continuing its journey through Big Rock's labyrinth of metal tanks, the porridge-like mush is cooled and strained. Now, fermentation can begin: yeast is added to the mixture and converts sugars into alcohol and carbon dioxide. One-third of that carbon dioxide is removed from the tank through a system of hoses; the rest, Foster chuckles, "gets into the atmosphere, it just takes a longer route -- I can see you know what I'm talking about."

Station 5: Filtering
On his last stop through the network of tanks, Foster explains filtering, one of the final steps before producing drinkable beer. In other breweries this is also the time the beer is pasteurized, but not at Big Rock -- the process can affect the beer's carefully crafted flavour.

Station 6: Packaging
Moving onto a neighbouring building, the beer is portioned into cans, kegs and bottles. The area is a series of conveyer belts and machinery, as well as coolers the size of small houses.

"How'd you like that in the backyard of the local seniors home?" Foster asks the retirees.

Station 7: Drinking
The tour over, Foster portions out samples sizes of Big Rock's brews: Traditional (Foster's favourite), the low-cal Jack Rabbit, Honey Brown Lager, Grasshöpper (a wheat ale), XO (a pilsner-style lager), Black Amber (stout), Big Rock Pale Ale, Warthog (a mild brown ale) and Irish-style McNally's Extra.

For one guest this is her first taste of beer, despite growing up above a watering hole in the United Kingdom. She's hesitant at first, but eventually comes around; after all, after the last two hours she probably knows more about beer than most life-long aficionados.

The Big Rock Brewery tour runs every Tuesday, Wednesday and Thursday at 1:30 pm. The Big Rock Grill, the brewery's on-site restaurant, is open Monday to Friday, from 11:30 a.m. to 2 p.m.