How to do a Forced Ferment

[Martin G]

There is mention of this test in other threads, but given how useful it is I was surprise that there doesn't seem to be a thread about it.

The point of the test is to know what your final gravity is (or could be) before your main batch has finished. This can be helpful in diagnosing if there is a problem or not during the main ferment, but the reason I personally like it so much is that I can safely chill and put the beer in a cask, keg or bottle at 2 points above gravity without priming.

There seem to be a variety of ways to do it, but most involve fermenting a sample large enough to test at a warm temp. The temp range suggested varies between 25C and 27C. Regular rousing or stir plate is also recommended. Not much is mentioned about the vessel to use, I have found a small conical is good as you can easily see how active the yeast is because the little bubbles run up the side. I have not seen much about airlocks etc, but to my mind it would make sense to do this under an air lock especially if using a stir plate, otherwise the wort may be too oxygenated and the yeast may multiply rather than ferment and that would slightly affect the density (probably not too significant).

The Yeast book just advises to take a sample after pitching and others suggest collecting separate wort and over pitching. I like to take a sample on day one of fermentation. Obviously sanitation is still important as otherwise you are not testing the same culture.

One problem is that you need a separate warm place for the test, I plan to build a cabinet for starters and forced ferment, but have not got around to it yet.

Hope this is of interest.

[jimp2003]

There is a good how-to guide on Kai Troester's site HERE

[darkonnis]

The little 5L kegs will fit a 1L conical flask in, build your stir plate into that and then use something like a brew belt or other lower power heater to heat the inside. Usual STC business from there on in. Alternatively, you could use the airing cupboard and stirplate? Kai Troester as jimp as pointed out has loads of good info on it which will undoubtedly be or more use than my suggestion

[Martin G]

The little 5L kegs will fit a 1L conical flask in, build your stir plate into that and then use something like a brew belt or other lower power heater to heat the inside. Usual STC business from there on in. Alternatively, you could uing cupboard and stirplate? Kai Troester as jimp as pointed out has loads of good info on it which will undoubtedly be or more use than my suggestion

(Sorry if quote has changes, my curser kept skipping up for some reason)

Interesting idea, I've been using an electric radiator in a small room as a temporary solution, about as un-elegant as it gets. Have bought myself a £6.95 room thermostat to control some sort of small heat source, because they are cheap and easy to use, accuracy is not critical. Not found the heat source yet, or built the little cabinet / container.

Somebody else has posted that they set up a water bath on the stir plate with a aquarium heater, which sounds like an easy approach as well.