CMOS Brewing

In 1939, with war clouds shadowing a pacific English countryside, the Journal of the Institute of Brewing (IOB) took time to discuss a matter it had periodically addressed earlier: the best wood for beer casks and comparing American and “Memel” oak for same.

The 1939 piece was probably the last time the IOB examined this, or in any detail. After the war, sought-after Crown Memel oak staves (CMOS), from Lithuanian forests and other areas in the Baltic, proved almost impossible to buy. If brewers could find them, the staves were frequently marred by shell splinters and other damage from the late war.

In time, as older Memel casks in British inventories literally tapped out, lined American oak casks were relied on, with metal casks (steel, aluminum) finally taking over.

Why were these American casks lined on their interior? The author of the 1939 article, William Lindsay, explained:

The timber used for brewery and distillery casks is invariably oak. The origin of this oak is usually Russia or North America; other kinds have been tried but not successfully. The properties essential for cask timber are:—
(1) Neutrality—to preserve the flavour of the beer.
(2) Tightness—to prevent leakage.
(3) Breathing ability for maturing the liquor.
(4) Bending ability to prevent breakages.
(5) Hard wearing.
Russian or Polish oak has a fine balance of these properties and is shipped in staves of standardised quality and measurement. The staves are known as Crown Memel Oak Staves, and is the wood commonly used for beer casks. American oak is closer-grained and denser and consequently harder and tighter, but for that reason it is more difficult to remove objectionable flavouring matters. When used for beer, an internal lining is necessary.

[Note added Nov. 20, 2019: I later found a link to the coopering film mentioned, a graphic document indeed; see this post].

Hence, American wood casks were lined to keep out “objectionable flavouring matters”. What were these? Earlier articles in the Journal described them as particular flavours imparted by the oak species typical of Arkansas and other North American forests supplying the staves.

One IOB account called it a “cocoanut” taste, and noted CMOS casks did not carry the taste. And any tannic taste resident in CMOS was easy to leach out, William Lindsay explained in 1939, as the grain was looser than for American oak.

This disliked American taste was, evidently, the bright vanillin and coconut flavours familiar to anyone who knows bourbon whiskey or Chardonnay wine. And it’s not just American wine, today, but wines from many parts of the world, aged in whole or part in American oak. (French and other non-U.S. woods are also used, but relatively little due to the scarcity and extra expense).

The plain fact is that British brewers did not like the American oak taste in pale ale or porter. There is a documented exception for Guinness stout, shipped in the wood barrel days in (charred) American oak casks.

But English, Scots, and Welsh brewers did not want these casks, generally. When they first had to use American casks during WW I they lined them to keep the taste out.

This stratagem must have enjoyed limited success as American oak in the interwar years was not common in British breweries.

British casks made from CMOS were not generally lined although experiments had occurred off and on from the 1800s to employ enamel and other barriers. The reason was not to keep out a bad wood taste, but to minimize souring from microflora in hard-to-clean wood surfaces.

Tastes change, and the coconut, vanillin taste in modern, barrel-aged craft beer is familiar to anyone who knows the beer scene. Use of American, unlined oak barrels to store beer is just one practice now normalized that didn’t exist generations ago.*

A further point to reflect on: has an historical brewing project been done to employ Memel oak casks? Not as far as I know. Some wood currently used in mashing, fermentation, or even for some casks may, in some traditional U.K. breweries, be CMOS, English oak, or other European wood. But such usage is historical, scattered, and not methodical to my knowledge.

As Memel oak is available again, in enough quantity surely to make casks and probably other brewing vessels, it is surprising no brewer has taken up this cause.

Below is an example of the beautiful oak that helped shape the greatness of British beer for centuries. It is from Ekenex JSC, a Lithuanian wood exporter, see the webpage here.

Note how straight the logs are, which favoured traditionally splitting for staves (no sawing). The wood was famous for having few knots and blemishes. While not as hard as American white oak (quercus alba), and somewhat more porous, Memel was durable enough for beer purposes. It was “the” choice of British brewing for centuries.

*Cloudy beer is one. Sour beer is, for by and large, another.



2 thoughts on “CMOS Brewing”

  1. Hi Gary ,
    Nice post , a bit of a backwater in the beer history world .
    And from what I’ve heard English oak was ,highly prized

    • Thanks Edd. As far as I know, no one has called for a recreation project that uses Memel wood or English: once again if anything has been done, I’m happy to know details.

      English oak indeed was highly prized but even around 1900 it was felt hopeless to find very much of it due to the historic cutting of the stands for HM navy and so much more…


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