Tim H in the comments to the last post had asked about the dry-hopping of stout and porter, pointing to some evidence it was done. Dry-hopping means adding a handful or more “dry” (unboiled) hops to the beer when barrelled or sometimes when stored in a vat or tank before barreling.
At p. 400, here, from A Textbook of the Science Of Brewing (1891) by Edward Moritz and George Morris, you will read that dry-hopping was generally not used for stout and mild ale.
The reasons are evident from the way Moritz explained the advantages of dry hopping. It was primarily for bouquet and taste in pale ale, and also to stimulate an after-fermentation for long-stored beers. Export stouts were the latter case, so that Brettanomyces yeast would consume the non-fermentable (by normal brewers yeast) dextrins and complex sugars.
In contrast, for mild ale a fresh, sweet quality was sought, with the malt to the fore. The hops play a lesser role versus the pale ale family.
Porter was increasingly sold fresh in the 1800s and correlatively maltiness was a signature, with a roasted malt flourish. I think it likely a flowery or herbal note was felt to clash with the malty character of new porter or stout and only a neutral bitterness was wanted, as say Guinness has today.
Certainly porter as handed down before the craft era, in my experience, did not have a strong hop smell and taste: Sinebrychoff Porter, Carnegie Stout, Anchor Porter, Molson Porter, the surviving U.S. regional porters, Guinness, Murphy, Beamish, Sheaf Stout, Lion Stout, the East European porters – none had a pungent hop smell from dry-hopping that I can recall.
Many of these beers survive, and remain unchanged in this regard.
It’s in tune with what Moritz wrote and he was a highly regarded brewing scientist of the era.
To my recollection Victorian brewing writer Frank Faulkner stated the same thing, or in substance. I recall as well similar statements in issues of the Journal of the Institute of Brewing.
Did some breweries diverge from a rule of thumb? Yes, Moritz himself noted this. But this was not typical, judging from his comments and other factors I’ve noted.
20th century practice is less significant as gravities had fallen. Dry-hopping can encourage stability, as Moritz noted too. Nonetheless it was only with the onset of craft that one started to see dry- or aroma-hopped porter and stout, particularly with citric New World varieties.