I've dove into my collection of Gravity Book analyses to spear all the Milk Stout examples. And there are quite a few. All I can say is: what a diverse bunch.
For a start, the gravities are all over the shop. As you can see, the original, Mackeson, had a very respectable OG of 1060º in 1929. To put that into perspective, Guinness Extra Stout was around 1055º between the wars. The examples in the table vary from 1036º to 1066º. Though admittedly the high one is a Belgian example from Lamot. Though, at 1064º the strongest UK-brewed dexample isn't that far behind. The overall average of 1053º is probably about the same as the average for all Stouts.
Some of the rates of attenuation surprised me by how high they were. I wouldn't expect a Milk Stout, with all that unfermentable lactose to get higher than 65% apparent attenuation. Yet there are a few pushing 80%. Not sure how they achieved that, unless the quantity of lactose used was quite small. At the other end, there are a few at 50% attenuation of less. Which is more like you would expect. The overall average of 64% is higher than I would have guessed.
Note that the price per pint didn't always necessarily reflect the strength of the beer. At a time when beer strengths weren't gerneally known, it was relatively easy for a brewer to overprice a beer.
What I see is typical of fairly new styles. initially, different brewers interpretations vary considerably in strength and character, but eventually settle into a similar pattern. We'll see if that's true as I slowly creep through the decades.
|Milk Stout 1925 - 1937|
|Year||Brewer||Beer||Price per pint d||OG||FG||ABV||App. Atten-uation|
|1927||Ashton Gate Brewery||Milk Stout||9||1052.4||1015.7||4.76||70.04%|
|1930||Beer & Rigden||Milk Stout||1054.4||1027.1||3.50||50.18%|
|1932||Carter, Milner & Bird||Milk Stout||11||1044.2||1013.4||3.99||69.68%|
|1936||Wm. Younger||Milk Stout||10.5||1063||1014.7||6.30||76.67%|
|1937||Calder Alloa||Milk Stout||1055.75||1022.25||4.32||60.09%|
|1937||Seed, Richard||Milk Stout||11||1052.9||1011.3||5.42||78.64%|
|Whitbread Gravity book held at the London Metropolitan Archives, document number LMA/4453/D/02/001.|
|Younger, Wm. & Co Gravity Book document WY/6/1/1/19 held at the Scottish Brewing Archive.|
|Thomas Usher Gravity Book document TU/6/11 held at the Scottish Brewing Archive.|