GOOMBA! wrote:It was my understanding, and someone please correct me if I'm wrong, that BP malt was usually used for porters.
It depends whom you ask, and whom you believe. From what I've read, Roasted Barley or Black Malt can make your beer a Stout, but that Porters historically got their darker color from the Amber and Brown Malts. I think of Robust Porters as lighter stouts, which is pretty much the definition given to porters after the invention of stouts.
Of course, then I've heard the argument that beers with smaller amounts of roasted grains (e.g. Beamish and Murphy's Stouts) are really Porters that got lumped into Irish Stouts simply due to 1) geographical location and 2) the inclusion of Roasted Barley.
Ray Daniel's book (the only one I've got that has a history of Stouts, hence the only one I can truly reference) points out that between 1820 and 1900, Guinness "provide[d] further evidence of the management's willingness to change with the times . . ." by, amont other things, a "rapid adoption of black malt" and the "elimination of brown malt from porter and stout formulations" (Daniels, Ray, "Designing Great Beers" pg. 308). Based on that, and the rave reviews I've read about Amber and Brown malts, I would exclude BPM and Roasted Barley from a Porter recipe (If included in the grist, I'd probably just consider it a stout) and use amber and brown malts instead for Porters, and consider any beer with a significant amount of Roasted Barley or Black Patent Malt a stout (with exceptions for slight use as a coloring agent or something where it obviously fell in line with the guidelines of another style).
Of course, Porter is effectively a revivalist style of beer, and there is SOOOOOOOOOO much blurring between Porters and Stouts, that it is probably impossible to say for sure unless you're going by the style guidelines. Even that is far from definitive since those rules don't necessarily count when you aren't trying to win a contest.
By the way, if I'm wrong or if there are other prominent theories about Porters a/o Stouts, I'd be curious to hear about it/them.