There’s some wonderful information in Peter Mathias’ The Brewing Industry in England 1700-1830, especially if you’re looking for funny details about the world of London brewers in the 1730s that could be hacked into alchemical-industrial conspiracy. For example, isinglass:
It’s basically made out of fish bladder, and it’s used as a “finings”–that is, you dump some of it into your finished beer (in powder form, I think, though I’ve never used it myself), and it pulls the yeast to the bottom. In other words, it clears up your beer, and it was the main way of doing so prior to mode recent industrial innovations like filtration and centrifuging. Don’t get me wrong: this stuff is still in use today, though in more highly processed form, in the production of traditional ales and beers, and of course among homebrewers. But in the 1700s in England, it was the industry standard, and was used by big breweries as well as small ones.
Its importance to the porter brewers of London lay in part in the perception that “clear” porter was more stable (in terms of resisting spoilage) than a cloudy porter, and could be aged for longer periods, which I think because of the malt being used was apparently necessary for porter at the time. (Indeed, porter was the first beer to be stored and the brewery until it was in condition for the publican to be serving it: prior to porter, “malt liquors” (i.e. beers and ales: see this post for more on the difference) had gone to the publican fresh, and it was up to said publican to manage the goods until they were ready to serve. Old-styled brewing practices were simply not as sanitary as they are today, and so whatever could be done to promote stability was seen as a positive.
However, according to Mathias in the early 1700s, the best (and really, the only useable) isinglass was made from Russian sturgeon. In England it was not only widely used, but also 100% sourced from Russia (though imported via the Low Countries, which at the time were under Habsburg rule). That sounds crazy, but I’d swear I’d read it somewhere else, too, in some book that’s… er, far from here.
Anyway, for a long time, every attempt to make isinglass in England–of which there were a number, including, in one case, using imported pickled Russian sturgeon! bleah!–ended up being failures. English attempts to manufacture isinglass domestically only succeeded when it was absolutely necessitated by the supply disruptions of the Napoleonic wars.
That left English brewers rather subject to the whims of the Russians, and to a lesser degree the whims of the merchants in, I’m guessing, Antwerp, which was under Habsburg rule. But then, at the time the Habsburgs were more into wine than beer anyhow (at least in Vienna), so it’s likelier that it’d be the Russians putting anti-English conditions on their produce… providing they had the inclination, and assuming they could find another market for it.