Dec 202004Fri

Sizing up the Rabbit Hole

SG 1.003 sugar

OK, time to get serious and see if we can push the ABV a little on what’s left of this batch. We started on 25 September in Port Erin with an OG of 1.046 and that same brew is now sitting in Onchan at 1.003. Ignoring the fact that I measured it at 1.001 when I bottled 39 clear flip-tops from this 25 litre bucket, I’m now left with two demijohns of questionable size filled with something that should be around 5.6% ABV.

Assuming that I want to get to around 9% I’ll have to find an additional 3.4% from a starting point of 1.003, which (according to the propaganda provided with the hydrometer) means it has a sugar content of -12.1 g/l, rounded to 1.005 which is the closest value on the chart. In order to get 3.2% (again, rounded to closest value found on chart) I’ll need a total of 53.8 g/l and since I’m starting with -12.1 that leaves me having to add 65.9 g/l of sugar for my 9% ABV. I have as much confidence in this approach as I do in the fact that I’ve got 2x one gallon demijohns of cider left after filling 39 x 500 ml bottles from a 25 litre bucket. It just doesn’t add up.

I measured the capacity of a glass demijohn just now to be equal to six bottles of wine plus 200 ml, so 4.7 litres in total. Multiplying 4.7 by 65.9 gives roughly 310 grams of sugar per demijohn to bring it from 5.6% to somewhere near 9% ABV, not allowing for volume lost to SG measurements and general sloppiness. I’m also not accounting for losses due to the alcohol tolerance of our natural yeast in this brew – heard somewhere that natural yeast as found in apples will tolerate up to 8% alcohol before it dies, so I’m potentially gambling with 1% ABV and a saving in sweetener. We’ll burn that bridge when we come to it, for now I’m adding 310 grams of sugar dissolved in a little water to the first of my two demijohns, while I think about what to do with the second one.

Instructions for adding sugar to achieve desired alcohol content
Instructions B-side: look-up table for gravity and sugar additions