The Magic Guinness Blend c.1939

Cover of the Guinness brewing manual.

When a colleague of mine told me that her father had been head brewer at Guinness’s London brewery and wondered if I might be interested in seeing his papers, I got a bit excited.

Finally, months later, we got round to visiting to check out what was in her collection. Based on a quick audit the answer is: everything.

We’ve agreed to take possession of the whole lot, catalogue it, copy bits we might be able to use for our own research, and then help with arrangements to have the important bits taken into appropriate archives.

For now, though, here’s a nugget from the handful of documents we brought away with us on Wednesday night: insider info on how Guinness gained its once legendary complexity at the blending stage.

This comes from a typed document in a plain brown wrapper written in 1939 and updated to take account of wartime brewing restriction. The copy we have seems to come from around 1943 but was in apparently still in circulation in the 1950s.

The first page bears the title ‘The Process of Brewing Guinness’ and the 46 pages that follow offer detailed notes on the basics of beer making (how hops are dried, for example) as well as specifics about Guinness.

Section header: "making up".

Here’s the section on ‘Making Up’:

Beer in storage vats [after fermentation] is quite flat and is cloudy and bitter and uninteresting to taste. Before it is ready for sale it must be ‘Made up’… Beer from say six different brews forms the basis. These are chosen in such proportions that when mixed with unfermented beer (i.e. wort that has been pitched but not allowed to ferment) known as gyle, their residues added to the fermentable matter of the gyle will give a suitable ‘Prime’. ‘Prime’ is the fermentable matter in beer after making up just as ‘Residue’ is the fermentable matter as the beer enters the storage vat. It is measured as the difference between the present gravity of the beer and its perfect primary.

In addition to these beers there are added:–

  1. Barm beer: this is the beer which is skimmed off from the skimmers with the yeast and is separated from the yeast in a filter press. It is intensely bitter but adds very materially to the flavour of the flat, uninteresting storage vat beer.
  2. O.B.S.: old beer storage is old acid beer that, like barm beer, improves the flavour of the finished beer although it is itself very unpleasant.
  3. Drawing: these are residues of made up beer which was not bright enough to put into the trade without further treatment. It is exactly similar in composition to made up beer.
  4. Finings: this is a solution of isinglass in storage vat beer. Only minute traces of isinglass are required but it brings about the very rapid sedimentation of all the floating particles which make the beer cloudy.

All the constituents of the make up are pumped into a ‘Racking Vat’ together and there allowed to stand for 24-48 hours.

So, there you have it. We sort of knew the gist of this but this is the most explicit explanation of the process we’ve seen in writing from a primary source, we think.