Scots brewer and designer James Steel (1821-1891) addressed the topic of vatting in his Selection of the Practical Points of Brewing and Malting, and Strictures Thereon, for Brewery Proprietors (Glasgow, 1878).
He confirmed what Herbert Edwards Wright wrote somewhat later: vatting – the storing of beer in large containers, the largest, for porter, famously holding thousands of barrels – was going out of style.
As Wright did, Steel referred to a particular quality resulting from holding beer a year or more, he called it “apple and other flavours”. One must bear in mind this was before the era of reliable mechanical cooling – the beers were held basically at ambient temperature. Together with microflora resident in the wood and the brewery environment, this encouraged production of esters and other compounds imparting special flavours to beer.
Flavours resembling Wright’s pineapple and pear, and Steel’s apple, could thus distinguish beers long-stored.
Also of course, Steel’s term “fined” referred to the clarity gained by long keeping, then viewed as highly desirable for beer. The final stage of fermentation, called cleansing, rarely resulted in limpid beers. A lengthy standing would do much to clear them, especially in large vessels, although a last treatment with finings was sometimes necessary.
Steel seemed to accept the decline of vatting more readily than Wright, but did feel it useful for porter due to porter’s inherently stable character which he attributed to its highly cured malt component. He noted however the continuation of long aging at Burton on Trent for its beer, i.e., for IPA vs. Scots and other ales, and that such storage was in normal beer casks or other smaller wood – no huge vats as in London for porter. Still, this long aging did impart the aged flavour.
Bass pale ale in particular has always had an apple note, Worthington White Shield too. However imparted today, it’s still in those beers, in all forms I’ve had.
Finally, Steel approved the practice of using “fillings”, or wort, to enliven long-stored beer. The longer beer was kept, the less likely it would be fizzy on exit from the wood. Adding wort, sometimes in a partial process of fermentation, would cause a new fermentation and result in a satisfactory head when poured. You would also get a mix of fresh and aged characteristics.
Steel states that the practice was used in Dublin – brewing author Frank Faulkner confirmed it in the 1880s – and by “provincial brewers”, which would take in Scots and English brewers outside London. For London itself, Steel said “retailers” performed the work, saving the brewers the trouble.
Presumably he meant publicans, although would publicans be easily able to handle adding the quantities needed to draught porter in cask in the cellar? I am not sure adding such a thing would have been lawful, in fact. Could Steel have meant some intermediate level of trade, acting on behalf of brewers, did the work? This area needs investigation*. But there is no reason to think an experienced brewer and brewing figure (via e.g., the Steel’s masher, still used in some British breweries) would misstate such an important point.
*Re-reading his account, it is possible he was referring to mixing old and new porter, not the part where the fillings are added. If so, presumably the fillings were already in the old beer. The pages of Steel dealing with vatting and fillings are set out below, via HathiTrust: