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Hydrometer potential alcohol scale very wrong

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JimboMarimbo

Member
Joined
Mar 16, 2023
Messages
13
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4
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.
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.
 
Thanks Guys, I'd forgot you have different brands in US - here's pics of the top end of the SR Hydrometer: the relevant numbers are on opposite sides of the thin glass tube, but if you follow the black bands across from the blue area down, you can see the 'potential' abv is 'off the scale' at 1.110 !
 

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