Gordon Biersch brewers appear to enjoy greater freedom in the merger between Biersch and Rock Bottom. (Nikki Kahn/The Washington Post)

The merger has meant a lot more freedom for Gordon Biersch brewers, but has tightened the leash on their counterparts at Rock Bottom.

Gordon Biersch locations still have to keep five standard German-style brands on tap at all times and release four set-in-stone seasonals at the appropriate times. But the brewers are being granted considerable leeway in crafting “gap” beers to fill the down times between seasonal releases.

Last summer, brewer Kevin Blodger of the Gordon Biersch in Rockville released a “Gose,” an obscure eastern German-style ale flavored with coriander and salt. It was so well received that Blodger will likely repeat the recipe in 2012. On Dec. 28, Grant Carson of the Tyson’s Corner Gordon Biersch will tap a Rauch Dunkelbock, a strong dark lager made with 60 percent beechwood-smoked malt. Carson previewed the beer at R.F.D. Washington’s holiday tasting on Dec. 15; first sip brought out those bacony, phenolic notes typical of Bamberger rauchbiers, but it quickly was replaced by a depth of bittersweet chocolate flavor.

What’s more significant, Gordon Biersch for the first time is allowing its brewers to experiment with non-German styles. Blodger was set to tap a hoppy, American-style pale ale this week. In late January/early February, as part of a new Brewer’s Select program, all three local Gordon Biersch restaurants will unveil unique house beers. Blodger has a barley wine in the works. Scott Lasater at the Washington Gordon Biersch plans to tap a Belgian-style dubbel. And Carson will offer a saison, an IPA and possibly a Vienna-style lager.

“We still need to brew within the Reinheitsgebot,” notes Carson, referring to the German purity law that mandates only four basic ingredients (barley malt, hops, yeast and water). “So nothing too crazy, no fruit beers.”

Nevertheless, “everybody at the company is really excited,” adds Blodger, who is anxious to show that “we’re not just a bunch of corporate drones.”

Before the merger, each Rock Bottom brewpub offered a unique lineup of beers. Now, brewers are required to toe the line by keeping four year-around beers on tap at all locations: Rock Bottom Kolsch, White Ale, IPA and Red Ale.

“We’re being stigmatized because we’re all brewing the same beers, but we picked award-winning recipes that have a lot of hardware behind them,” protests brewer Dave Warwick of the Arlington Rock Bottom. The Red Ale, for instance, is based on the Raccoon Red formulated by Geoff Lively of the Bethesda Rock Bottom, winner of numerous Great American Beer Festival medals.

Both Warwick and Lively, however, stress that they’re still allowed considerable freedom in brewing a rotating dark beer and a once-a-month seasonal release. For about the 12th year in a row, Lively released his Anniversary Ale, but this year for the first time he added a dry-hopping with Amarillo, Mt. Hood and Cascade varieties, which contribute a spicy, herbal underpinning to the fresh ginger and sweet orange peel traditionally added to the beer. (He was also planning to tap one-, three- and five-year-old versions of his Atom Smasher barley wine.)

Warwick harnessed his creativity to formulate a gluten-free beer, a light ale fermented from sorghum and brown rice, which should be on tap now. He’s pitching the beer at celiac disease sufferers who can’t ingest barley, wheat or other common grains without the proteins damaging their digestive systems.

“It has an acquired taste, but a pleasant taste,” he says of the gluten-free offering. The plan is to keep it on tap for six months and make it a permanent selection if it sells well. The Arlington Rock Bottom will sell the beer over the bar as well as in 64-ounce growlers to go (and even in kegs, if the quantity permits). It will also be discounted for $1.50-a-pint Wednesdays, says Warwick.

Warwick has named his creation Nikki’s Gluten Free Ale after a friend who stopped by last June for his Jazzberry Raspberry tapping and woke up ill the next morning. She thought she was simply hungover, but a doctor later diagnosed her problem as gluten intolerance.

“I learned that one in 105 Americans are celiacs,” notes Warwick. Some are born with the condition, while in other cases, the disease manifests itself in adulthood. There are several bottled gluten-free beers on the market, such as Redbridge and New Grist, but brewpub offerings are much scarcer.

Will Nikki drop in to sample her namesake brew?

“She better!” laughs Warwick.