A pressure valve fitted to a gas in fitting for a Cornelius keg. If I added an overpressure valve to this, it would be a spunding valve. (It’s got a manual pressure release, so I supposed it could be thought of as a manual spunding valve, but man that could be dangerous if you capped the tank too early and forgot about it. Don’t do that.)

This is the third and final part of an article on kräusening. 

Kräusening is adding fermenting beer to a lager that has just finished primary fermentation. The active yeast in the fermenting wort help clean up diacetyl (and aldehydhes) before the beer is lagered. The yeast also produce carbon dioxide (CO₂) and this gives brewers who kräusen an option to carbonate their beer by “capping the tank” — sealing the vessel that has fermenting kräusen beer in it to trap the CO₂. Commercial brewers who do this have their tanks fitted with a spunding valve — a valve that holds pressure up to a certain point, and releases excess pressure above this level. If a tank can withstand 20 PSI, the beer can be carbonated to serving levels at lager fermentation temperatures. You can try this at home, if you make your own spunding valve.

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