Fermenting vessels in WW II

Pretty much everyone fermented in open vessels of some description. Though their form and shape varied considerably.

They were universally fitted with attemperators: metal pipes inside the fermenter through which cold water could be pumped to control the temperature of the wort. The development of the attemperator was one of the key technological innovations of the late 19th century. They allowed brewers to completely control fermentation temperatures and brew through the summer. Aiding, too, improved consistency and quality in the beer produced.

The two simplest were rounds and squares. Which were just open-topped vessels which were either round or square. Their size varied hugely, though they were rarely more than 100 barrels or so.

Sometimes the whole fermentation was performed in a round or a square, but they could also be used as part of a dropping fermentation or in conjunction with a Burton union set.

Skimming system
This was the simplest, and the most common, type of fermentation vessel. A single round or square vessel was used and excess yeast simply removed by skimming it from the top. For this purpose, a parachute was usually employed. This was a funnel-like device which was dragged across the vessel just above the level of the wort, causing the yeast to fall down through it.

The wort was roused at regular intervals to keep the yeast in suspension. The frequency of this rousing was determined by how flocculant the yeast was. The more flocculant it was, the more frequent the rousing.

Dropping system
A popular method of fermentation, especially in the South of England, was the dropping system. Fermentation began in a tall, relatively narrow, cylindrical vessel. After a period of time which might vary from as little as a few hours to a couple of days, the wort was transferred – “dropped” – to a lower shallow, square vessel.

As with most fancy fermentation systems, one of the principal aims was to remove excess yeast from the wort. Though dropping also effectively roused the wort and promoted a vigorous fermentation.

The time of dropping varied. At some breweries it was after 24 hours – even sooner in the case of Fullers where it was sometimes less than 12 hours. At others it wasn’t until the beer had hit half gravity.

The big advantage of the system was that it tended to produce a cleaner beer.