Old hydrometer

[MuckyNeighbour]

Hi all, my hydrometer is of unknown provenance and I’m guessing it’s quite old. I don’t understand 2 of the three scales and the 3rd is simply “pot abv” which, although clearly understandable, seems too good to be true as there are too many factors which would affect final abv. I’ve attached photos of the scales: can anyone advise what the other two are and how I should interpret them please?

 

[Matt_W]

Hi all, my hydrometer is of unknown provenance and I’m guessing it’s quite old. I don’t understand 2 of the three scales and the 3rd is simply “pot abv” which, although clearly understandable, seems too good to be true as there are too many factors which would affect final abv. I’ve attached photos of the scales: can anyone advise what the other two are and how I should interpret them please?

comparing to a modern hydrometer in front of me now it would appear the first photo is SG (as it says at the bottom), the second photo is potential abv and the third is sugar lbs per fluid oz i guess.

On mine the pot abv makes the assumption that it ferments out to 1.000. For example on mine 1.038 is 5% and 1.076 is 10%. If you put them in a abv calculator then you get those results.

Sugar on mine doesnt give units but it appears to be g/L.

 

[Victor Churchill]

I believe the intention of the 'potential alcohol ABV' is that you make a note of the initial value at the start of fermentation, and take a reading at the end and subtract the end value from the start one. Some older hydrometers do use that wording.

 

[MuckyNeighbour]

I believe the intention of the 'potential alcohol ABV' is that you make a note of the initial value at the start of fermentation, and take a reading at the end and subtract the end value from the start one. Some older hydrometers do use that wording.

I hope that’s it: my Black Forest Stout was reading pot abv of 16.5%

 

[MuckyNeighbour]

I hope that’s it: my Black Forest Stout was reading pot abv of 16.5%

Today it’s reading 1% so I’ve either made a soft drink or rocket fuel

 

[An Ankoù]

comparing to a modern hydrometer in front of me now it would appear the first photo is SG (as it says at the bottom), the second photo is potential abv and the third is sugar lbs per fluid oz i guess.

On mine the pot abv makes the assumption that it ferments out to 1.000. For example on mine 1.038 is 5% and 1.076 is 10%. If you put them in a abv calculator then you get those results.

Sugar on mine doesnt give units but it appears to be g/L.

I agree pretty much with Matt except that the final scale certainly isn't lbs/fl oz as you can't dissolve that much sugar in a fluid ounce of water. I think it's more likely to be pounds and ounces of sugar dissolved in a gallon of water ranging from 2 oz of sugar in a gallon to 3lb 12 oz in a gallon. Note, too, that the spefcific gravity scale is calibrated at 60 degrees F, which is about 15C. There's nothing wrong with it being old, the question is whether it's accurate, Check it by putting in some tap water at 60 degrees F / 15C and it should sink as far as the 00 on the scale, read at the bottom of the meniscus.

 

[An Ankoù]

I agree pretty much with Matt except that the final scale certainly isn't lbs/fl oz as you can't dissolve that much sugar in a fluid ounce of water. I think it's more likely to be pounds and ounces of sugar dissolved in a gallon of water ranging from 2 oz of sugar in a gallon to 3lb 12 oz in a gallon. Note, too, that the spefcific gravity scale is calibrated at 60 degrees F, which is about 15C. There's nothing wrong with it being old, the question is whether it's accurate, Check it by putting in some tap water at 60 degrees F / 15C and it should sink as far as the 00 on the scale, read at the bottom of the meniscus.

Forgot to say that the third scale is of particular use to wine makers.