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You'd think March was Porter month from the amount I've posted on the topic. In reality, every month is Porter month here. You might have guessed from the title that this post discusses the steps from fermentation to serving.

The stuff about the temperature sort of tallies with what I see in brewing records. In the 1820's, Barclay Perkins were pitching at 63º to 67º F after which the temperature rose to around 80º F. Though the stronger Stouts were pitched much lower, at 58º to 59º F. By the end of the 19th century, their pitching temperatures were down to 60º to 62º F.

"The different worts after boiling are spread out thin in the coolers, and their temperature brought down to between 60 and 70 degrees, at which all the three worts are mixed together in a great vessel called the guile tun or square, where yest being put to it the liquor is fermented. The temperature at which the wort is set to working in the square, and the heat at which the several mashes are made, have greater influence than any other circumstances upon the quality of the beer. The greater the working heat is, the more rapidly the fermentation proceeds : therefore in summer, when the natural heat of the air is such that the working will advance perhaps more rapidly than the brewer wishes, he counteracts this by cooling the wort down as low as possible : on the other hand, in cold weather the fermentation must be encouraged by commencing it at a greater temperature : in general it may be stated to be between 60 and 70 degrees, at the discretion of the brewer, and in some degree regulated by the kind of porter he wishes to produce, and the malt from which he has extracted his wort. The fermentation is continued in the square as long as the head of yest which floats upon it continues to increase in depth ; but when the head shews signs of diminution the liquor is fit for cleansing. This is putting it into a great number of small casks, which, by dividing the beer into small quantities, lowers its temperature and tends to check the fermentation. The same end is also attained by causing the yest to flow off as fast as it is produced, and keeping the casks always filled up as they diminish by working, to leave no room for a head of yest to gather upon the surface of the beer. After the fermentation is concluded the beer is put into immense casks called store vats, where it is kept till wanted for sale. By keeping it begins to clear itself, and grow fine ; but it is seldom kept long enough to become perfectly so. It is when wanted drawn off from the store vats into casks, and then sent away ; and the consumer puts into the cask a small quantity of fining, sent out with the porter by the brewer, who calls it in the rough when his liquor requires fining.

The finings are made of isinglass dissolved in sour beer brewed from the wort of the fourth mash, or sour beer obtained from the waste of any of the processes. A small quantity of this fining beer being put into the cask precipitates the minute fecula, and soon renders the liquor quite fine. The flavour of the draught porter in London is almost universally obtained by compounding two kinds, the due admixture of which is palatable, though neither are good alone. One is mild, and the other stale porter; the former is that which has been lately brewed, and has rather a bitter mawkish flavour ; the latter has been kept longer, and is in some degree acid. This mixture the publican adapts to the taste of his several customers ; he effects the proportion of mixture very readily by means of the Beer Pumps, described under that article (see pl. 24). These will be found to have four pumps, but only three spouts, because two of the pumps throw out at the same spout. One of these two pumps draws mild, and the other the stale Porter; and the publican, by dextrously changing his hold to the next handle works, either pump, and draws both kinds of beer at the same spout; and an indifferent observer supposes that since it all comes from one spout it is entire butt beer, as the publican professes over his door, and which vulgar prejudice has decided to be the only good porter, though the difference is not easily distinguished."
“Pantologia: A new cyclopaedia Vol IX”, 1813, (doesn’t have page numbers)
Using sour beer for preparing finings has one pretty obvious disadvantage: it's a good way of introducing an infection. You can't help wondering how often such finings buggered the beer in addition to clearing it. Later in the century brewers moved over to using other dilute acids in which to dissolve finings.

I'm not sure what to make of the final section about the strange beer engines. Is it to be believed? Was this really common practice? Certainly a couple of decades later brewers were advised not to send out their Porter mild, but to always blend it themselves. Mostly to reduce the possibility of the publican adulterating the beer.

And the flavour descriptions: mild Porter was "bitter mawkish" and stale Porter "in some degree acid". I think I can understand what the second means. But the first? The word mawkish has fallen into disuse and doesn't really say a lot to me.

That might be it (at least for a day or two) about Porter. But you never know, I might find something else I just have to share.