I have been looking at some on-line priming calculators. They mostly seem to be for beer and seem to be based on having about a volume of C02 in the beer post fermentation. Is this likely to be the same for cider?
My concern is that I will sometimes leave my cider in secondary for some time to mature before bottling and wonder if over that time the residual C02 in the cider falls to insignificant levels. So I don't know whether to use the priming calculator figure for 2.5 volumes (6g/L of sugar) or the generally accepted "rule of thumb" for priming of 10 g/L of sugar.
Up until now, at bottling time I have worked on using enough sugar (or juice) to raise the FG by two gravity points per volume of carbonation (say, to 1.004 or 1.005). This seems to work OK, especially when I add enough extra sugar for the touch of sweetness that I want. I simply bottle and monitor carbonation with a flip top test bottle fitted with a pressure gauge.
When the gauge reaches close to 2.5 bar, I open the test bottle, do a “taste test” (of course), and if it is OK, pasteurise the other bottles with a hot water-bath to stop fermentation and end up with some sweetness from whatever sugar hasn’t been fermented.
I have tried a new yeast on the market and it seems to take the sharp edge off fully fermented cider, so extra sugar isn’t needed. I am happy to go down the “roughly10 grams of sugar per litre” path for bottle carbonating. However, the 2.5 volumes of C02 from 10g/L of sugar would be on top of the C02 (if any) already in the cider, and the calculators seem to take this into account.
I ferment small batches of 5 litres. So, bottling at 1.005 means about 50 grams of sugar (10 g/L), but plugging the numbers (5L, 20C temperature, 2.5 vols of C02) into any of the calculators comes up with only 30 grams of sugar (6g/L)... a bit of a difference. So what is the answer? If i go bck to first principles (C02 per gram of sugar=4.7, g/L of C02=1.977), I end up with 10.5 grams of sugar, near enough to 10 g/L.
Why the difference, or am I just fussing about nothing. BTW I am ready to bottle a Red Delicious/Granny Smith Cider which doesn't need any sweetening but I don't want to overcarbonate. Any thoughts?
Cheers!