When to take the final potential alcohol reading?

Hi everyone,

I know I need to subtract the final potential alcohol from the original, but when do I take the final reading. This is probably a really dumb question, which would explain why I can't find the answer anywhere.

My kit says to take the second SG reading when I put the beer into the carboy from the primary fermenter, but surely this isn't the final values.

I took another reading when I bottled the beer, but I think I messed up because I put the priming sugar in before I took the reading.

If I had taken the reading before I put the priming sugar in would that be the correct time to take the final reading? Or is the final reading taken when I open the bottle after it's primed?

I've already learnt a whole load from this site, and I only found it yesterday.

Cheers, Colin

I measure the final SG when I bottle- before the priming sugar is added. Sometimes I can get enough beer out of the fermenter after racking to the bottling bucket to get a reading.

Fantastic, thanks RichBrewer. I had a feeling that was probably it, but I failed Physics at school because I always came to the wrong deductions, so I like to check with someone else now. =)

Best to take at least 2 FG readings, actually. One when you think fermentation is done (to get a base reading) and the second at least 2 days later to confirm if the FG is the same. If it is, bottle/keg away. If it's dropped, hold off, let the yeasties do their thing and come back a few days later (repeating with the initial & then secondary gravity tests).

The final reading is the one that is the same as the reading taken three days earlier. Trying to time your fermentations is a bad idea. When the gravity has been the same for 3 days, then it's done.

Ah, ok. More good answers. That makes sense. I've just set off my second kit, so I'm pretty must just following the instructions. I guess they're setup, so that more than enough time is left for the fermenting, hence they only seem to mention the SG readings in passing. My next beer might be from a recipe (if I'm feeling brave enough) so that information will all be very useful.

Thanks everyone.