Heavy Seas Brewing in Baltimore will ship out two beers in cans this month. One is Loose Cannon, an American-style IPA. (Heavy Seas Brewing)

What started as a trickle has become a torrent.

In 2002, the number of small breweries canning beer stood at one. Now, according to the Web site www.craftcans.com, that number has swelled to 290.

Lost Rhino Brewing in Ashburn rushed out 12-ounce cans of two of its beers — Rhino Chasers Pils and Face Plant IPA — in time for Memorial Day cookouts. Heavy Seas Beer in Baltimore plans this week to ship two canned brands: Loose Cannon, its American-style IPA, and Davy Jones Lager, an amber lager in the Anchor Steam mold. Devils Backbone Brewing in Lexington was prepping for a second canning run of its Striped Bass Pale Ale this month. And DC Brau has doubled the number of canned offerings, with Penn Quarter Porter, On the Wings of Armageddon (a super-hoppy imperial IPA) and summer seasonal El Hefe Speaks (a Bavarian-style wheat beer) joining its three pale ales.

But the banner headline might be the conversion of the industry’s leading naysayer.

Jim Koch, chairman of Boston Beer, once had little regard for beer in aluminum cylinders. When he purchased a Cincinnati brewery in 1994, he got rid of the canning line. In 2005, he circulated a Beer Drinker’s Bill of Rights that stated in part: “Beer shall be offered in bottles, not cans, so that no brew is jeopardized with the taste of metal.”

Fast forward to 2013: The first 12-packs of Samuel Adams Boston Lager and Samuel Adams Summer Ale cans are stacked in supermarkets. Samuel Adams Oktoberfest will join them later this year.

“What changed is the quality of the can lining,” explained Koch of his about-face. “Beer used to pick up a solvent-like character from the solvent-based linings. Now they use water-based linings.”

What’s more, “the new linings are more flexible,” he contends, less likely to tear and allow the beer to come into contact with metal. “They’ve proven out, but I wanted to make sure. They crossed a threshold two years ago.”

Nevertheless, Koch says he has spent the past two years and about $1 million designing a better beer can. At first glance, it looks identical to the standard model, but closer examination reveals a wider lid and an opening positioned farther from the edge. The design, says Koch, forces you to open your mouth wider, letting in more air, which enhances the beer’s aroma and flavor.

“It makes a slight but noticeable difference,” he maintains.

Boston Beer isn’t the only craft brewery pioneering a new design. Sly Fox Brewing has found a foolproof way to eliminate the glug-glug-glugging of a can being poured. The Pottstown, Pa., brewery recently became the first North American company to market a beer can with a lid that peels off completely, turning the can into a drinking vessel. Sly Fox has released two brands — Helles Golden Lager and Pikeland Pils — in the package.

Sly Fox’s range extends into New York and New Jersey, and there are plans to expand into the District, Maryland and Virginia by the end of the year. But the 360 End cans (as the peel-off design is called) will probably be limited to Pennsylvania. Brian Thiel, regional sales manager for Crown Cork & Seal (the can’s manufacturer), concedes one major problem: anti-littering laws in 36 states might prevent the can’s proliferation. Most of those laws were passed during the 1970s, when sharp-edged pull-tabs were lacerating bare feet and winding up in the gullets of wildlife. Thiel notes the 360 End can is designed to be environmentally friendly. Crown is promoting the can for use at ballparks and concert venues, where the lids can be collected and recycled. The cans also could reduce the need for disposable cups.

“If we had more lawyers on our staff, we’d try to get these laws overturned,” says Tim Ohst, Sly Fox’s brewery operations manager, with a laugh.

Another advance in canning is the number of sizes available. Indeed, breweries can now peg the volume of the container to the strength of the contents. San Francisco’s 21st Amendment Brewerysells its potent Lower De Boom barleywine in 8.4-ounce mini-cans, perfect for a before-bedtime nip. Conversely, Oskar Blues in Longmont, Colo., and Brevard, N.C., recently released its lighter, more refreshing Mama’s Little Yella Pils in 19.2-ounce “stovepipe” cans, ideal for a hot summer afternoon’s quaff.

Oskar Blues, which fomented the revolution 11 years ago by releasing its Dale’s Pale Ale in cans, is experimenting with a more radical package: a pint-sized metal bottle with a resealable screw-top cap. So far the brewery has released two beers in the container: Chaka, a Belgian-style pale ale, and the Deuce, a hoppy brown ale. (Both are collaborations with Sun King Brewery in Indianapolis.) Distribution has been limited to Colorado and Indiana, says Oskar Blues spokesperson Chad Melis, but the brewery would like to go national. The big obstacle is cobbling an assembly line to fill and seal the uniquely shaped cans. Oskar Blues has been packaging the metal bottles on a two-head manual filler, which can’t spit out enough liquid for the brewery’s 32-state territory.

But that’s a problem even for many breweries sticking with the standard flat-top can. Heavy Seas is contract-canning its brands at F.X. Matt Brewing in Utica, N.Y., which possesses a higher-speed packaging line. Seven Virginia breweries have deals with Old Dominion Mobile Canning, an Ashland company with a portable cannery, which can package up to 60 barrels in a day, according to the company’s Web site. Owner Mike Horn says he hopes to line up 20 to 30 clients within the next two years.

“They did their first run with us,” says Mitch Roessing, marketing manager for Wild Wolf Brewing in Nellysford, Va., which cans its Alpha Ale and American Pilsner. “We open the garage door, they slide the machinery in, we work six to eight hours. They pick it up, and the mess is gone with them.”

“It’s an easy way to dabble in canning without going into debt to buy a high-speed line,” notes Josh West, operations manager for Devils Backbone. And it’s an avenue for even the smallest and newest microbreweries to join the rush to aluminum.

Kitsock is the editor of Mid-Atlantic Brewing News.