Do-It-Yourself Hobby Comes to a Head : Beer: It’s a tailor-made keg of brew that’s ready in two weeks. Enthusiasts prefer concocting their own recipe rather than swilling store-bought brands.

More than two years have passed since Tor Mohling brewed his first batch of beer. Since then, he has made cases and cases of the stuff.

He makes an event of it, enlisting friends to stir the bubbling wort (that infusion of malt and simple sugars that will ferment into beer) and experimenting with every batch, always trying some new spice or flavor or grain. The brews have ranged from raspberry wheat to cinnamon and clove to his own favorite, imperial stout.

“Once I started doing it, it was a landslide,” said Mohling, a graduate student and former brewer for a local brewery. “It fills the kitchen with great smells; it’s satisfying, and you end up with your own beer.”

Mohling may not fit the profile of the average home-brewer, whom the American Homebrewers Assn. in Boulder describes as about 35, with an annual income of $57,000 and 4.75 years of brewing experience. But he is in on a hobby that is rapidly gaining popularity.

In the past five years, Americans have become obsessed with expensive, personality beers. As a result of people wanting to try their hands at the art or wanting to save money, the home-brew industry has experienced 20% to 35% growth each year, according to the 20,000-member AHA.

“Home-brewing definitely picked up about five years ago,” said Walt Dudley, an employee at Denver’s Wine & Hop Shop. “It’s become really trendy and a lot of people have gotten into it. Home-brew stores are popping up all over.”

The smell--not the taste--is the first thing one notices upon entering a home-brew supply store. Home-brew supply sales have grown to a $7-million-a-year industry, but that has not diminished the friendliness, the sawdust-on-the-floor layout or the trademark malt-and-grain aroma of most outlets.

“Like any hobby, there are a million toys to make it more fun,” said Anne Trowbridge, another Wine and Hop Shop employee, during a tour of the small store with the creaky floor. She is winner of this year’s Queen of Beer Homebrew Competition.

Shelves are packed with yeast, malt, spices, scales and Irish Moss flakes. A loft of sorts is laden with huge plastic buckets and other paraphernalia. An odor of something musky and fermenting wafts in from somewhere.

The basic starter kit, which includes makings for the first two cases of beer, runs about $50 to $60. Subsequent batches cost about $20 for two cases--much cheaper than premium beer at the liquor store.

Trowbridge says she is a “beer snob.” Her favorite beer costs $11 a six-pack at the liquor store.

“You do it (home-brewing) to kind of support your habits,” she said.

The store sponsors a club, one of about 400 nationwide, providing an arena for competitive tasting. The get-togethers range from a once-a-month meeting of groups with names like “The Unfermentables” to a full-scale, seven-day, national home-brewing conference called “BrewStorm ’94.” This year’s event, which was held June 19-25 in Denver, attracted more than 3,000 entries.

When asked where an aspiring home-brewer should begin, Trowbridge headed straight for the cookbook rack and held up what she called “the bible of home-brewing,” Charlie Papazian’s “The New Complete Joy of Home Brewing.”

The book helps, but most home-brewers shyly compare horror stories of batches gone bad. Timing, temperature, bacteria and the gods of fermentation are all variables that can combine to produce ill-tasting brews.

“We spend a lot of time on the phone (answering questions),” Dudley said. “You’ve got to make it fun; it’s someone’s hobby. If they hit a brick wall every time, they’ll quit.”

There is another option for people who need more hand-holding, who cannot dedicate entire refrigerators and bathtubs to brewing, or whose spouses or pets cannot tolerate two weeks of the beer belching during fermentation. In both Colorado and California, microbreweries cater to the do-it-yourselfer.

At Hamilton Gregg Brewworks in Hermosa Beach, customers can choose among 45 different beer styles, from light lagers to porters and stouts. They spend from 1 1/2 to 2 1/2 hours mixing the brew, then return two weeks later to bottle and label it.

“We provide the recipe, guidance, ingredients and equipment,” said coowner Patricia Spiritus. “But they actually grind their own grains and measure out their own hops.” They can even design the labels.

Customers get four cases of beer for their trouble--48 22-ounce bottles. The price ranges from $80 to $130, depending on the beer style, she said, plus $30 for the bottles--which are reusable.

The Beer Shop in Boulder offers a similar service. People can brew their beer on the premises, with supervision and without dealing with the variables that can foul up a batch of beer.

A customer can come in--even a complete novice--and choose from 87 recipes, said owner Doug O’Claussen. It takes about two hours to mix the ingredients into wort. The staff then “baby-sits” the beer, controlling the temperature and environment, while it ferments and ages.

“The customer comes back exactly two weeks later, and we wheel out a beer keg,” O’Claussen says. The cost of the keg, which may also be bottled into about six cases, runs between $60 and $90, roughly the same as the cost of brewing a batch at home.

Spiritus noted that brewpubs--taverns that brew their own beer--have failed to catch on in Los Angeles, as they have in some other areas. “That’s why I think we’re popular, because you can’t find fresh-brewed beer,” she said.