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Hydrometer potential alcohol scale very wrong

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JimboMarimbo

Member
Joined
Mar 16, 2023
Messages
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Location
Lichfield England
Stevenson Reeves’ printing error?

Stevenson Reeves’ wine and beer hydrometer is in general use and trusted to measure SG accurately; however the markings on the ‘potential alcohol’ scale differ from all the scientific tables I have seen, and from around 1.040 upwards become less and less accurate, indeed, towards the highest readings ‘out of the blue range’ they become completely ‘wrong’. I feel sure that a renowned and trusted manufacturer must be aware of this and I wonder why what I perceive to be a glaring error should persist over the decades this instrument has been in production.

For example at SG 1.100 Stevenson’s black line for potential alcohol reads a whisker under 16% abv, whereas, for example CJJ Berry’s chart shows 13.4% and the scientific VINOLAB website says 13.56%, Brewers Friend broadly agree around 13.26%. Moving on, Stevenson then seems to ‘lose it’ with SG 1.160 matching their last line of 17%, whereas Berry and Vinolab say 14.42%, and then the last marking of SG 1.120 on the hydrometer not even offering a guess, whereas the others say a steady 16.44%, interestingly still less than Stevenson said for SG 1.160.

Odd, perhaps some older and wiser heads than mine could offer a reason why this obvious wrong reading should persist, or am I missing something here?
 
Likely because every yeast strain has a different attenuation and alcohol tolerance so it's a wild guess for the most part. Accurate measurement of ABV uses OG/FG calculations so just use it that way.
 
Likely because every yeast strain has a different attenuation and alcohol tolerance so it's a wild guess for the most part. Accurate measurement of ABV uses OG/FG calculations so just use it that way.
I mean, you're not wrong, but even 100% attenuation and no tolerance issue isn't getting close to 16% from 1.100
 
Stevenson Reeves’ wine and beer hydrometer is in general use and trusted to measure SG accurately; however the markings on the ‘potential alcohol’ scale differ from all the scientific tables I have seen
A picture is worth a thousand words.

I mean, you're not wrong, but even 100% attenuation and no tolerance issue isn't getting close to 16% from 1.100
It's potential alcohol, which I would think assumes a solution of 100% fermentable sugar in water and 100% real (not apparent) attenuation. But FWIW, 15% is 1.11 on my no name hydrometer.
 

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