Measuring the alcohol content of my brew - OG/FG Readings

[dansullivan]

Hallo hallo - Ive done one brew kit already and it worked pretty well, and Im on my second now. However, I had no idea of the strength of my final potion. So, Ive gone off and bought a hydrometer. The instructions on it are, however, dire. Ive looked at a good few websites this morning to see how to calculate the ABV% and Id just like to clear something up.

The hydrometer that I have does have a scale on it that indicates alcohol%, however, the instructions that it came with do not mention this and the web does not seem to mention this either - is it redundant due to inaccuracy?

So, on to what seems to be the more popular method of calculating alch. content... I gather it is a function of the Starting Gravity and Final Gravity (Ive got a load of formulas showing what to do with these (speaking of which, can you recomend a formula yourselves)) - when exactly should these readings be taken? Some sites say that the SG should be taken b4 adding the yeast, others after - I would have thought that b4 makes more sense.

and when do I take the FG? in the kits Im using there are 2 stages of adding sugar - one at the beginning when I add a kilo of sugar to the fermentation tub, but then I add more (1/2 teaspoon/ pint) to the pressure barrel or to the bottles. So if bottling the beer, I can take an FG reading just before I bottle it but obviously not after. so is the answer that you just have to do it as late in the process as possible, and then make a guess as to the effect of the extra sugar? seems a bit inaccurate given the .001 readings etc that Im taking!!!

And finally.... I cant help tinkering with things myself... as I have 40 odd pints at the end of the process, Im more than happy to sacrifice a few in the name of trial and error, adding what ever comes to mind to various bottles at the bottling stage. can you recomend anything interesting that I can add at this stage - honey seems like an obvious choice instead of sugar, are there any pros/ cons about this??

Also bottles that I bottled this second time round, when Ive opened them the whole thing pretty much turned to fizz, violently firing out of the top of the bottle. Is this because I had not let the fermentation complete properly, and so the 1/2 teaspoon sugar carried on the fermentation proper??

sorry about the essay - I really have looked all over trying to sort this out!

Thanks
Dan

[Buzz]

There's a recent thread HERE on the subject of measuring your ABV. I measure the OG just before pitching the yeast and the FG before bottling/barreling. The extra priming sugar will not make too much difference.

[Martin the fish]

Yep, me too. I use a simple formula. OG minus FG X 0.129= ABV. Give or take a fraction.

[vacant]

Ethanol boils at 78.4C.

Just measure out 100cc sample before you drink it and heat it to 85C. The alcohol will quickly boil out. What volume is left? Hey presto, you can work out the ABV%.

Er, has anybody actually done that?

[edit1now]

You have to allow for the fact that what boils off is a "racemic mixture" of 95% alcohol/5% water, due to physics and chemistry...