Hydrometer scale sg vs potential alcohol

[Ebob01]

I have been looking at a lot of home brew recipes recently and I was thinking that they all seemed to have too much sugar. I thought they will all either end up as rocket fuel, or depending on the yeast used will end up sweet.

My hydrometer looks like the one I have seen in almost every online homebrew store, Wilko etc. It has the blue band for 'start wine' red for 'start beer' and yellow for bottling. I think I got it on Amazon a few years ago.

On this hydrometer an sg reading of 1090 corresponds to a potential alcohol of 14.5%.

I've looked at charts online which suggest this actually corresponds to 12%.

This is potentially infuriating as it means I have been watering down all my wine, not so annoyed about it not having as much alcohol but the extra water will have affected the flavour and made it thin. I've got 12 bottles of elderberry I did last autumn which came out looking much paler than expected.

If anyone's got a spare minute could they please check theirs and post the reading? Would be much appreciated.

 

[Drunkula]

Just checked my Stevenson one and 1.090 lines up with the 12.25% alcohol scale - that would be if it brewed out to zero specific gravity (sg), but if it's gauged for sugar and it brewed out completely dry that would get you 13.8% and the sg be lower than 1.000.

https://homedistiller.org/wiki/calcs/calcs_sugar_sg.htm
The alcohol scale usually isn't there to take a direct reading at the start but to use when you know the difference between the start and final gravities. So for instance if you started at 1.090 and ended at 0.990 that would be a difference of 100 (0.1 for pedants), so you'd read up to 1.100 on the hydrometer then turn that to see where it hits the alcohol scale. On mine it's almost 14%

So just take your start and final gravities and work out the alcohol from that using an abv calculator. Some use the formula start - end * 131.25 so 13.1% for a 100 point difference. Yup, different from what my hydrometer says, different from what the ABV calculator in BeerSmith says, but the same as what this says :

https://www.brewersfriend.com/abv-calculator/
Lots of people use the 131.25 rule so you might as well go with the flow.

 

[Gerryjo]

When taking SG be it for wine, cider or beer I use a hydrometer and a refractometer and both tally up. I only use the hydrometer then for FG as I can't be bothered with the conversion calculations with Brix.

 

[The Baron]

If it is wine you are fermenting it generally finishes below 1.000 and on a average red it would be about 0.995 or even lower, that is for a standard red finish but if you want a sweeter red it may finish nearer the 1.000. Do not use the alcohol reading on the hydrometer as exact just as a guide as it will probably base the potential on a 1.000 FG but as I have said most wines will finish below 1,000 and therefore the alcohol amount will increase above the guide on the hydrometer

 

[kelper]

As above and beers often finish at 1.010.

 

[Ebob01]

Thanks for the replies.

I wonder if the discrepancy is due to whether the hydrometer has a reading which states 'alcohol' or 'potential alcohol'

Potential alcohol implies that if every last bit of sugar was used then that's what the alcohol content would be.

I think maybe the 'alcohol' scale accounts for the fact that when fermented dry the specific gravity falls below that of water due to the alcohol being less dense.

Mine states potential alcohol. So if I do the example as described by drunkula above, then I read off a value of 16% potential alcohol corresponding to 1.100. Which is what you 'could' get if you started off with a sugar content which corresponds to that specific gravity. However I'm thinking that if your scale reads alcohol, then what it will tell you is the alcohol content based on your starting minus final gravity.

At 1.090 my potential alcohol is 14.5%, however using drunkula's hydrometer you would do 1.090 minus .990 and read off at 1.100 which would give a similar value for the alcohol.

This still doesn't explain why most recipes I have across seem to have a really high sugar content which would either result in a really strong or a really sweet wine.... I guess it could be that's how the authors like it....

 

[LED_ZEP]

There's also the chance that your ingredients could affect the gravity readings. For example I've made a sugar wash recently that has split corn kernels in it for flavour only and the unconverted starch will lead to a higher start and end reading. The only way I can work out the potential ABV is by knowing how much fermentable sugar is there and the volume of liquid and work out the potential from that.

 

[The Baron]

You would probably be better using a ABV calculator by putting in your OG and expected FG to give you a more accurate forecast. There is one in this forum I believe on the top line under calculators

 

[Ebob01]

Ok thanks I'll take a look