The retrobike beer went on cool this morning, that is the level of sugar has fallen in the beer to a point where we want to almost stop the fermentation, so we pump a glycol / water mix around jackets which surround the tanks. This will drop the temperature from 20 degrees Celsius down 5 -6 degrees.
A little sugar is always left in the beer, this helps give body and support the malt and hop flavours, and the amount is determined in part by when you put the chillers on. Prepare for a little science
Distilled water has a specific gravity (density) of 10.00, that is there is very little in it. As the sugar levels increases so does the density and with it the specific gravity. Our beer had an original specific gravity (original amount of sugar) of 1041.5 and we put the chillers on when the gravity reaches 1013. (see the photo attached reading 1012).
The fermentation will continue very slowly over the next few weeks (in the fermenter and in the cask) until it reaches a specific gravity of 1010. The sugar that has been digested (1041.5 – 1010) = 31.5 degrees of fermentation which when chucked into a calculation gives us an ABV of 4.1%....ta dah!!!
The beer is still looking sludgy (see photo) as yeast and protein are still in the process of settling out. Over the next 2 – 3 days it will clarify a little as stuff settles under gravity.
Next up...clarity tests!