I bang quite a lot about parti-gyling. How it wasn't one wort per beer. No, the worts were blended together post-boil, with some of each wort going into each beer, just in different proportions.
That's how everyone parti-gyled. Except for Truman, at times. When they blended both pre- and post-fermentation. I'll be upfront: I have no idea what the point of this process was in the 19th century. Something similar was done during WW I, but then there was a point. Some beer was fermented at a higher gravity for yeast production, then blended with weaker beer after fermentation. Here, though, I really can't see the point.
Let's get on with it, then. This was a Stout parti-gyle from 1st March 1886. Four worts came out of the coppers, with these gravities:
41 lbs per barrel (1113.6º)
33.8 lbs per barrel (1093.6º)
16 lbs per barrel (1044.3º)
9 lbs per barrel (1024.9º)
What happened to these is where the weirdness starts. Because 6 barrels of the strongest wort were siphoned off "to C.R.", presumably that means Country Runner, one of Truman's Porter variants.
The four worts were blended up to create three beers:
162 barrels @ 34 lbs per barrel (1094.2º)
158 barrels @ 28 lbs per barrel (1077.6º)
305 barrels @ 25.5 lbs per barrel (1070.6º)
These were left to ferment away. At racking time, though, there was a second blending, leaving:
Imperial Stout 82 barrels @ 34.1 lbs per barrel (1094.5º)
Double Stout 244 barrels @ 28.8 lbs per barrel (1079.8º)
Single Stout 315 barrels @ 27 lbs per barrel (1074.8º)
80 barrels of Imperial Stout have been blended with Double Stout and Single Stout, bumping up the gravity of Double Stout by 2.2º and Single Stout by 4.2º. I really can't see what the point of the messing around was.
Next the log gives the quantities of each beer racked:
Imperial Stout 82 barrels
Double Stout 246 barrels
Single Stout 297 barrels
Before you say anything, I know the numbers don't quite add up.
This wasn't some weird one-off. Truman always brewed their domestic Stouts this way, right up until 1909 at least. (That's the last Stout brewing book I have).
I really can't see a point to this fiddling. Only thing I can think of, is it's connected to the new taxation system introduced in 1880. But that still dooesn't explain the reasoning behind it.