"It's from Mark," LaPierre replied, referring to Iron Hill's co-founder Mark Edelson. "His background was in pharmaceutics, so we always measure in centigrade."
Roberts let that sink in, then he took another jab: "And you guys use specific gravity, too, right?"
Ooohhh . . . in brewer speak, that's a low blow.
Specific gravity, a measurement of the amount of sugar in beer wort, is a scale typically used by amateur home brewers. The pros use a scale known as Plato degrees.
LaPierre shook his head and muttered something about how "the previous owner really abused this equipment."
Ah, yes, the equipment. That's what brings these two fellows together on this morning.
It's a 12.5-barrel, stainless-steel brewhouse made by Newlands Systems of Canada - a basic-looking setup you'd find in many a small brewery. An overhead mill sprays a shower of crushed grain into a mash tun filled with hot water, and the porridgelike mixture steeps for an hour or so. The liquid is siphoned into a kettle where the wort is boiled with hops before it's cooled and sent to the fermentation tank.
It's the way brewers have made beer for centuries. But this otherwise generic equipment has a distinctively Philadelphia history.
The story goes back to the late 1990s, when LaPierre and Roberts both worked at the now-closed Dock Street brewpub on Logan Square, both as waiters and part-time brewers.
LaPierre was supposed to take a job as brewer at a new brewpub to be built at Reading Terminal by the now-defunct Red Bell Brewing Co. The place was beautiful, with lots of wood, big TVs, a huge bar and, behind a set of glass windows, the Newlands brewing system.
The job fell through when the brewpub's opening was delayed, and LaPierre headed to Harpoon Brewing in Boston.
Then Dock Street purchased the facility, renamed it Independence Brew Pub and handed the head brewer's job to Roberts. While the brewpub suffered from troubled financial backing and steep rent, Roberts managed to turn out excellent ales for several years.
Until the morning in August 2007 when, as the mash tun steamed with a bellyful of grain, sheriff's deputies showed up and told him, "Get out. Leave now."
The pub owed close to $800,000 in back rent. The kitchen's food was donated to the city's homeless and the doors were padlocked.
Roberts returned to the brewhouse only once, to empty the now ruined wort. Not long after that, Iron Hill bought the system and put it into storage. (Dock Street was reborn in 2007, when it opened a brewpub in West Philly.)
Where it sat until three years ago, when LaPierre, now back in the area with Iron Hill, oversaw its installation at what is now the busiest brewhouse in the burgeoning regional chain.
As LaPierre adjusted a water-flow valve, Roberts, "the previous owner," admired the hissing machinery.
"It's been so long," he said, kneeling to look below its boiler. "It sort of takes me back."
LaPierre descended from a short ladder and hit the wet tile floor gently.
"OK, we're all mashed-in," he said. "Let's take a break. Want a beer?"
Roberts and LaPierre's collaborative beer is a re-creation of the Thomas Jefferson Ale they once brewed at Dock Street. The beer, based on a recipe Thomas Jefferson made at Monticello 200 years ago, is a bit stronger (9.5 percent alcohol) than the similar version now brewed at Yards.
Their ale, named 2 Logan TJ, will debut at Iron Hill (124 E. Kings Highway, Maple Shade) on Wednesday. The two brewers will talk about their collaboration at 5:30 p.m.
Don't get them started on Plato degrees.
"Joe Sixpack" is by Don Russell, director of Philly Beer Week. Contact him at firstname.lastname@example.org. For more on the beer scene, sign up for his weekly e-mail update at joesixpack.net.