Tuesday, 27 October 2020

Fermentation in WW II

One process which seems to have been pretty much totally unaffected by the war was primary fermentation. Presumably, as there was little scope for saving energy or labour.

In general, though the exact details varied across breweries, fermentation took place between 60º F and 70º F. Very strong beers were often pitched a degree or two cooler, but had a similar maximum temperature.

The exception being, of course, the handful of specialist Lager brewers, like Barclay Perkins. To take them as an example, fermentation were between around 45º F and 55º F.

Despite what you may have been told, Scottish brewers didn’t ferment at near Lager temperatures. As this fermentation record for a William Younger Mild Ale.

William Younger 6th August 1941 XXX
  heat OG
pitching 62º F 1036
day 1 AM 65º F 1030
day 1 PM 66º F 1027
day 2 AM 68º F 1020
day 2 PM 69º F 1018
day 3 AM 64º F 1015.5
day 3 PM 57º F 1015.5
day 4 AM 56º F 1015
day 4 PM 56º F 1015
William Younger brewing record held at the Scottish Brewing Archive, document number WY/6/1/2/78.

It looks like the wort has been allowed to heat itself for the first two days, before the attemperators were turned to drop the temperature down to 56º F. This is a pretty typical fermentation profile not just for William Younger, but for other Scottish brewers, too.

The process at Barclay Perkins was generally similar, with the yeast pitched at a little over 60º F and hitting a maximum temperature of around 70º FL

Barclay Perkins 11th April 1941 X Ale
  heat OG
pitching 61º F 1031.6
12th April 9:30 64º F 1028
14:25 66º F 1025
20:25 67º F 1022
13th April 8:15 70º F 1014.5
14th April 10:00 70º F 1008
17th April 11:15 59º F 1008.5
Barclay Perkins brewing record held at the London Metropolitan Archives, document number ACC/2305/01/624.


Barm said...

Does it say the attemperators were turned on? because by day 3, going by the gravity, the primary fermentation is mostly done in wort of that strength, so you might expect the beer to cool down again naturally anyway.

Ron Pattinson said...


it doesn't say so explicitly in the William Younger logs, but there are always certain marking in the logs just before a rapid fall in temperature. In some breweries' logs, it is specifically mentioned.