I no longer trust the calcs on here

[Devonhomebrew]

I typed in 1040-1010 and well the calc. on here told me that it was 4% ABV
Working in a microbrewery i have learnt some equations:

(SG-FG) X 0.129 = ABV

So apply this to my gravity's

(1040-1010) X 0.129 = 3.87% can someone explain this to me?

I also have top up equation and grain to water equation

 

[spudnic]

I can't see the problem? Are we only talking 0.1% if so then that's not that bad

 

[Devonhomebrew]

No im just wondering why the forum calc told me it was 4% and my equation tells me its 3.87%?

 

[stonegrey]

0.13% not sure it it is worth getting worked up over.

the calc i use is (OG - FG) /7.46 (1040 - 1010)/7.46 = 4.02% + 0.5% for priming.

which is even worse, but the method Coopers use.

there are many methods, and all will get you in the ball park.

 

[calumscott]

Yup, it's all educated guesswork unless you have a spare mass spectrometer knocking around...

 

[Devonhomebrew]

Ahhhh okay just the barowner/brewer its a brew pub uses this equation.

 

[jonewer]

The degree of error kicked out by the different equations is going to be far less than the degree of error in your hydrometer reading and subsequent secondary fermentation.

Its a bit like getting worked up that the distance from London to Sydney is stated as 17000km rather than 16983.034284756193948429384974km.

 

[dennisking]

The degree of error kicked out by the different equations is going to be far less than the degree of error in your hydrometer reading and subsequent secondary fermentation.

Its a bit like getting worked up that the distance from London to Sydney is stated as 17000km rather than 16983.034284756193948429384974km.

I thought it was 16983.034284756793948429384975

 

[jonewer]

The degree of error kicked out by the different equations is going to be far less than the degree of error in your hydrometer reading and subsequent secondary fermentation.

Its a bit like getting worked up that the distance from London to Sydney is stated as 17000km rather than 16983.034284756193948429384974km.

I thought it was 16983.034284756793948429384975

Philistine!

 

[Devonhomebrew]

Mate i was using brewers hydrometers the ones that are 80 quid each when i was wondering this in my mind the scale is from 1039-1046 on a much bigger scale so it was very to scale.

 

[jonewer]

Mate i was using brewers hydrometers the ones that are 80 quid each when i was wondering this in my mind the scale is from 1039-1046 on a much bigger scale so it was very to scale.

Scale smale. You are subjectively taking two readings from an instrument that is temperature sensitive. You take corresponding subjective readings from the thermometer and plug it into an equation to adjust and read accordingly.

The beer hasnt been sterilised so theres always going to be additional fermentation going on and then most people dump some more sugar in which means the OG is not the OG and the FG is not the FG.

Determining the %ABV of homebrew is a more a matter of well-informed guesswork than scientific analysis.

 

[Devonhomebrew]

I was mainly wondering why the forum was telling my it wa 4% but now i know why coz they use a different equation.

 

[Aleman]

The other thing to remember is that there are different equations, and they all give slightly different results.

The constant 0.129 is only valid for a narrow range of gravities . . . fine if you are brewing in that range, but not so good if you are brewing stronger/weaker beers.

I would assume, that as you are working in a commercial brewery, you need to know the abv for duty purposes? If this is the case then the only equation that matters is the one provided by HMCE (Section 30 ). Now this is the

OG-FG * f = abv%

Where f is a non constant fudge factor "The value of 'f' is not constant because the yield of alcohol is not constant for all fermentations. In lower strength beers, more of the 'sugars' available for fermentation are consumed in yeast reproduction than in producing alcohol."

If you have excel (This works for 2003) Then enter the OG in Cell A1, The FG in Cell B1 (Don't forget the Decimal point) then paste the following formula into cell C1 (formatted as percentage to 2 decimal places).

=(IF((A1-B1)<=0.0069,(A1-B1)*1.25,IF(AND((A1-B1)>=0.007,(A1-B1)<=0.0104),(A1-B1)*1.26,IF(AND((A1-B1)>=0.0105,(A1-B1)<=0.0172),(A1-B1)*1.27,IF(AND((A1-B1)>=0.0173,(A1-B1)<=0.0261),(A1-B1)*1.28,IF(AND((A1-B1)>=0.0262,(A1-B1)<=0.036),(A1-B1)*1.29,IF(AND((A1-B1)>=0.0361,(A1-B1)<=0.0465),(A1-B1)*1.3,IF(AND((A1-B1)>=0.0466,(A1-B1)<=0.0571),(A1-B1)*1.31,)))))))&IF(AND((A1-B1)>=0.0572,(A1-B1)<=0.0679),(A1-B1)*1.32,IF(AND((A1-B1)>=0.068,(A1-B1)<=0.0788),(A1-B1)*1.33,IF(AND((A1-B1)>=0.0789,(A1-B1)<=0.0897),(A1-B1)*1.34,IF((A1-B1)>=0.0898,(A1-B1)*1.35,)))))+0

I believe that we have used a different formula that is much more common in homebrew books as we are home brewers and do not need to be pedantic for HMCE duty purposes. I go by OG - FG / 10 to get an idea of abv 48-12/10 = 3.6% close enough for my purposes.

Like a lot of things in brewing there are many ways to make a beer, and achieve the results you need, while blindly learning 'some equations' is useful, quite often understanding the reasoning behind the equation, as well as it's limitations is much more important.

 

[Devonhomebrew]

The other thing to remember is that there are different equations, and they all give slightly different results.

The constant 0.129 is only valid for a narrow range of gravities . . . fine if you are brewing in that range, but not so good if you are brewing stronger/weaker beers.

I would assume, that as you are working in a commercial brewery, you need to know the abv for duty purposes? If this is the case then the only equation that matters is the one provided by HMCE (Section 30 ). Now this is the

OG-FG * f = abv%

Where f is a non constant fudge factor "The value of 'f' is not constant because the yield of alcohol is not constant for all fermentations. In lower strength beers, more of the 'sugars' available for fermentation are consumed in yeast reproduction than in producing alcohol."

If you have excel (This works for 2003) Then enter the OG in Cell A1, The FG in Cell B1 (Don't forget the Decimal point) then paste the following formula into cell C1 (formatted as percentage to 2 decimal places).

=(IF((A1-B1)<=0.0069,(A1-B1)*1.25,IF(AND((A1-B1)>=0.007,(A1-B1)<=0.0104),(A1-B1)*1.26,IF(AND((A1-B1)>=0.0105,(A1-B1)<=0.0172),(A1-B1)*1.27,IF(AND((A1-B1)>=0.0173,(A1-B1)<=0.0261),(A1-B1)*1.28,IF(AND((A1-B1)>=0.0262,(A1-B1)<=0.036),(A1-B1)*1.29,IF(AND((A1-B1)>=0.0361,(A1-B1)<=0.0465),(A1-B1)*1.3,IF(AND((A1-B1)>=0.0466,(A1-B1)<=0.0571),(A1-B1)*1.31,)))))))&IF(AND((A1-B1)>=0.0572,(A1-B1)<=0.0679),(A1-B1)*1.32,IF(AND((A1-B1)>=0.068,(A1-B1)<=0.0788),(A1-B1)*1.33,IF(AND((A1-B1)>=0.0789,(A1-B1)<=0.0897),(A1-B1)*1.34,IF((A1-B1)>=0.0898,(A1-B1)*1.35,)))))+0

I believe that we have used a different formula that is much more common in homebrew books as we are home brewers and do not need to be pedantic for HMCE duty purposes. I go by OG - FG / 10 to get an idea of abv 48-12/10 = 3.6% close enough for my purposes.

Like a lot of things in brewing there are many ways to make a beer, and achieve the results you need, while blindly learning 'some equations' is useful, quite often understanding the reasoning behind the equation, as well as it's limitations is much more important.

Cheers man so its all down to the equations cheer :