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I remember when I was a teenager (25ish years ago) the strength of a beer was given as a range of original gravity - say 1034-1039. This would be say a 4% then you'd have 1078-1080 which was good and strong like Tennents Super. I think the original gravity was shown with a degree symbol?
What did it mean and why was it discontinued?
Guesses:
OG (how sugary it starts off) is a predictor of alcohol content assuming adequate fermentation and nothing else going on (like daft freezing to remove water etc). You may as well use final alcohol content direct, since it's quantifiable (don't they use the difference between OG and final gravity?) and more easily understood
Knows....
All changed about 20 years ago with Eu regs and C and Ex / Trading Standards rules.
OG = Original Gravity , and gives an idea of how strong the beers might be . Big breweries used to be able to manipulate the ABV by over fermenting beers , therefore paying less duty . Duty was paid on the OG , not the ABV , so by starting with a lower OG the beer cost less to make .
The Degree is sign is correct , as OG is expressed as density , as the amount of sugar dissolved into liquid will make it denser , and is measured with a Saccherometer . This has to be temperature corrected using a table with temp V apparant density.
ABV = Alcohol by Vol . Expressed as a percentage , and is being phased out to be replaced with ALc. Vol. same thing different words .
4%, 6% etc is a bit easier to get to grips with than silliness like 1034-1039 or whatnot. Makes a lot more sense too.
ABV easier to translate into units too
5% means 5 units in a litre
Wait.. you mean it's no in shillings any more?
80/- is.
I have a Coopers European Lager kit on the go at the moment. The instructions tell me that the calculation for ABV is as follows:
ABV = ((OG - FG)/7.46) + 0.5
So assuming the OG is 1040 and the FG is 1005, that gives (35/7.46)+0.5, or 5.2% (to 1DP)
Now I was always led to believe that the ABV was approximately ((OG-FG)/10), which would work out at 3.5% ABV, so either something's changed or my original rule of thumb was a VERY rough approximation 😯