If you've spent any time hanging out with craft-beer drinkers, you know that even the mention of the word "cask" can send them into a frenzy. That's because cask-conditioned beers, with their mellow carbonation and slightly warmer serving temperatures, offer more pronounced flavors than their "regular" keg counterparts.

(If you've never tried cask ale, or don't believe the hype, here's my suggestion: Go to the Schlafly Tap Room, and order two pints -- a regular Schlafly Dry-Hopped APA and an APA from the cask engine. The differences in aroma and flavor will be eye-opening.)

The guys behind St. Louis' two International Tap House locations recognize the appeal of cask beer, which is why they've recently bought four firkins to keep the cask suds flowing. Here's how it works: iTap ships an empty cask to a brewery, which then fills it and sends it back with its next beer delivery.

"We know there is a demand and delight for cask beer, so we are making every effort to bring as many unique casks as we can to the bars," iTap co-owner Sean Conroy says. "It's yet another costly commitment iTap is making to improve the craft-beer scene in St. Louis. The margins are low, but the reward we feel is exceptional."

The first beneficiaries of iTap's new cask program were those in attendance at the Soulard location's Stone Tap Takeover last Thursday. Stone Brewing Co. filled an iTap firkin with Stone IPA dry-hopped with Simcoe hops.

The Soulard iTap will tap a cask of Odell Myrcenary, a double IPA, at 7 p.m. on May 5.

Other casks that will be coming soon to iTap (whether they go to the Chesterfield or Soulard location will be determined on a cask-by-cask basis):

• Rogue, beer TBA. "Something big and unique," Conroy promises.

• Ska, dry-hopped Modus Hoperandi.

• Boulder, Mojo Risin' Double IPA.