How do YOU convert BRIX to SG

[bobtheUKbrewer2]

I ask this because I have started to use a mash correction factor of 1.4 and I suspect something is wrong. A definitive list of 15 BRIX to 3 BRIX in 0.1 BRIX steps would be very helpful. All of us could check our calculations against it.

Also, how do you calculate ABV ?

thanks

 

[Veedo]

Beersmith!

 

[grathan]

I use brewing software or a chart.
http://www.brewersfriend.com/brix-converter/
http://www.fermsoft.com/gravbrix.php
http://www.northernbrewer.com/refractometer-calculator/

Not sure what you mean by correction factor. You could also multiply by 4.
so 15 brix = 1.060.

 

[eulipion2]

I use brewing software or a chart.
http://www.brewersfriend.com/brix-converter/
http://www.fermsoft.com/gravbrix.php
http://www.northernbrewer.com/refractometer-calculator/

Not sure what you mean by correction factor. You could also multiply by 4.
so 15 brix = 1.060.

A more exact formula would be 259/(259-brix)

259/(259-15)=1.061, but for a close estimate, multiplying by 4 is good enough.

 

[bobtheUKbrewer2]

are we allowing for alcohol in the fermenting wort?

 

[ajdelange]

Assuming Brix to be the same as °P they are calculated from SG by:

P = -616.868 + 1111.14*S - 630.272*S*S + 135.997*S*S*S

where S is the 20/20 apparent specific gravity. This is the "official" ASBC polynomial derived from the Plato tables and is, therefore, the "correct" formula for calculation of concentration from specific gravity in the USA.

The ASBC table (and thus the useful range of the polynomial) end at 1.083. The following polynomial is continuous in slope and ordinate with the ASBC polynomial at 1.083 and can be used at higher specific gravities. It does not have official status.

P = -584.6957 + 1083.2666*S -577.9848*S*S + 124.5209*S*S*S

The "Lincoln Equation" is a great way for getting quick answers and is quite good (less than 0.004 °P error) across the entire range of the ASBC table. It is derived from a second order fit to the Plato table:

P = (463-205*S)*(S-1)

One of the nice things about the Lincoln equation is that it is easy to invert:

S = (668 - Sqrt(668^2 - 820*(463 + P)))/410

Inversion of the ASBC polynomial is more difficult but can be done in closed form. It is actually simpler to use a numerical root finder than implement the closed form solution. Excel's Solver can be used but except for precise work the inverted Lincoln equation above is probably the most practical.

ABV can be determined from original and true or apparent extract using the Balling formula. See http://en.wikipedia.org/wiki/Gravity_(alcoholic_beverage)

 

[bobtheUKbrewer2]

many thanks ajdelange

 

[bobtheUKbrewer2]

now the bad news ajdelange - I do not understand what you are telling me.

Say my OG = 10 BRIX and it ferments down to 5 BRIX, what is my ABV, please?

 

[TrainSafe]

10 brix is approximately 1.040

5 brix is about 1.019-1.020

That translates to about 2.5% ABV

 

[ajdelange]

now the bad news ajdelange - I do not understand what you are telling me.

Say my OG = 10 BRIX and it ferments down to 5 BRIX, what is my ABV, please?

According to the Wikipedia article the 'Balling Factor' (from DeClerck) is

f = 0.39661 + 0.001709*P + 0.000010788*P*P

where P is the original extract. For OE = 10 °P

f = 0.39661 + 0.01709 + .0010788 = 0.4148

The estimated ABW is f*(P-m) = 0.4148*(10 - 5) = 2.07

The estimated ABV = ABW*SG_beer/0.79661

The beer finishes at 5 °P. Using the inverse Lincoln Equation its specific gravity is

S = (668 - Sqrt(668^2 - 820*(463 + P)))/410

= (668 - Sqrt(668^2 - 820*(463 + 5)))/410 = 1.0197

ABV = ABW*1.0197/0.79661 = 2.65%

 

[ajf]

I ask this because I have started to use a mash correction factor of 1.4 and I suspect something is wrong. A definitive list of 15 BRIX to 3 BRIX in 0.1 BRIX steps would be very helpful. All of us could check our calculations against it.

Also, how do you calculate ABV ?

thanks

I used to use Specific gravity = (Brix/(258.6-(Brix/258.2)*227.1))+1
I now use a different algorithm which gives slightly more accurate results, but which is far to complicated to express as a formula.

The above formula should give pretty accurate results if the sample is pure sucrose (which is the case with wines), but will be inaccurate when measuring beer wort which contain mostly maltose. The wort correction factor is intended to correct for this difference, and is applied by dividing the calculated SG by the correction factor.
Unfortunately the wort correction factor varies with the composition of the wort, but is typically 1.04, not 1.4.

-a.

 

[bobtheUKbrewer2]

everybody - can we simplify it please, how do you convert BRIX to SG PART WAY through the fermentation

start 10 BRIX day 3 7 BRIX finishes at 5 BRIX

 

[ajdelange]

Doesn't matter which day it is. The inverse Lincoln equation is still probably the most practical:


S = (668 - Sqrt(668^2 - 820*(463 + P)))/410

Or, if all you want is a rough estimate, multiply Plato (Brix) by 4, divide by 1000 and add 1 e.g. 7 Plato ~ 1.028 SG

 

[bobtheUKbrewer2]

thanks AJD

 

[Ondori]

Brix x 4 is what I do. Quick and easy

 

[ajf]

Doesn't matter which day it is. The inverse Lincoln equation is still probably the most practical:


S = (668 - Sqrt(668^2 - 820*(463 + P)))/410

Or, if all you want is a rough estimate, multiply Plato (Brix) by 4, divide by 1000 and add 1 e.g. 7 Plato ~ 1.028 SG

Neither of those solutions would work with a refractometer, where the refractive index is affected by the presence of alcohol, resulting in a Brix reading that is very inaccurate.

Using the example of a beer that starts with 10 Brix, and finishes at 5 Brix (and uses a wort correction factor of 1.04), Sean Terril's calculator gives
OG = 1.0384, FG = 1.01, and ABV as 3.6%
Promash gives
OG = 1.03844, FG = 1.00862, and ABV = 3.91%
Beersmith gives
OG = 1.039, FG = 1.008, and ABV = 4.02%
These compare to your readings of
OG = ?, FG = 1.0197, and ABV = 2.65%
I must admit, I've never found any of these calculators to be particularly accurate, but your FG calculation is clearly wrong. I agree it would be correct if you were using a saccharometer, but not with a refractometer which requires a correction because of the presence of alcohol.

Because of this using the inverse Lincoln equation is not possible with a refractometer once fermentation has started.


-a.

 

[PDX_T]

everybody - can we simplify it please, how do you convert BRIX to SG PART WAY through the fermentation

start 10 BRIX day 3 7 BRIX finishes at 5 BRIX

Are you using a refractometer?

 

[bobtheUKbrewer2]

Let's simplify it even more - using a refractometer I get a value of 5 BRIX for a fully fermented wort that started at 10 BRIX - but the 5 BRIX is an average of the BRIX of the maltose remaining and the BRIX of the ethanol produced - so how do I calculate ABV ?

 

[abrix]

Honestly? With a hydrometer. You'll need to take a SG reading with a hydrometer and either convert your final SG reading to Brix or vice versa before estimating your ABV.

As ajf explained above, alcohol throws the refractometer reading off, so your 5 Brix reading is not something you can really use.

 

[PackerfaninSanDiego]

brix X 4 here too
calculator for ABV http://www.brewersfriend.com/abv-calculator/

 

[Yooper]

Let's simplify it even more - using a refractometer I get a value of 5 BRIX for a fully fermented wort that started at 10 BRIX - but the 5 BRIX is an average of the BRIX of the maltose remaining and the BRIX of the ethanol produced - so how do I calculate ABV ?

In short, you can't.

Refractometer measures the light refraction. Once alcohol is in the solution, the light refraction is skewed.

You can use correction software to help account for this, but I've never found one that is accurate for me, although many people use the software on Sean Terrell's website and say it's accurate for them.

 

[bobtheUKbrewer2]

but there must be correction formulae to allow for alcohol...

 

[ajdelange]

Let's simplify it even more - using a refractometer I get a value of 5 BRIX for a fully fermented wort that started at 10 BRIX - but the 5 BRIX is an average of the BRIX of the maltose remaining and the BRIX of the ethanol produced - so how do I calculate ABV ?

You can't really. There is an MOA (ASBC Method of Analysis) for determining ABV of beer by the use of a refractometer but it is only applicable for checking that a particular lot number of a particular brand of beer (i.e. the same beer brewed over and over again) is within spec. It requires that the refractometer be calibrated for the particular beer.

Formulas for 'conversion' of refractometer readings after the onset of, or even at the completion of, fermentation abound but are notoriously unreliable. Refractometers aren't really much good for measuring the OG of wort either as they are calibrated for pure sucrose solutions. The frustrating thing is that they are often pretty accurate for wort but are occasionally off by 1 or more °P and there is no way (that I know of anyway) to tell when you are in one of those situations.

Refractometers in brewing are great for detecting when the sparge is coming to an end and for telling when fermentation is complete but not of much use for anything else unless you do the calibrations required of the MOA (and that requires distillation with a digital density meter or pycnometer or gas chromatography.

I place so little faith in refractometers that when OP wrote 'Brix' it never even occured to me that he was using a refractometer but rather assumed that a hydrometer was being used. I would never recommend any formula for conversion of 'Brix' as derived from a refractometer reading to SG, especially once fermentation has started.

 

[ajdelange]

but there must be correction formulae to allow for alcohol...

Yes, for a particular beer and determining that requires the calibration I mentioned in my previous post.

 

[bobtheUKbrewer2]

OK - after mash we have a solution of maltose and various other fermentable and non fermentable "sugars" and our hydrometer reads 1.050

We allow fermentation to come to an "effective" end and measure the SG with the hydrometer again, this time getting 1.005

Clearly the unfermentable sugars are making the SAME contribution to the SG, almost all of the maltose is now ethanol, so how do we calculate ABW or ABV ?

 

[kingogames]

I look at the other side of my hydrometer.

 

[ajdelange]

Clearly the unfermentable sugars are making the SAME contribution to the SG, almost all of the maltose is now ethanol, so how do we calculate ABW or ABV ?

With hydrometer readings you use the Balling formula as I detailed earlier converting SG readings to Plato with the ASBC formula. There are also dozens of simplified formulas based on the Balling formula of the form ABV = constant*(OG - FG). If you are converting SG and Plato back and forth with the 40 times conversion there isn't much justification for computation of the Balling factor. You aren't going to get that accurate an answer even if you do as the basis is Tabarie's principle which is iffy and you really don't know your effective OG because of evaporation etc.

 

[bobtheUKbrewer2]

my point is - at end of fermentation we have some maltose still, some unfermentables and some ethanol - so what is the hydrometer measuring/

 

[ajdelange]

The hydrometer measure the density of the solution normalized by the density of pure water at some specific temperature. The density of water is 0.998203 g/cc at 20 °C. If you add sucrose (or other sugars) to it its density increases and the specific gravity becomes greater than 1 depending on the amount of sugar. If you add no sugar but rather some alcohol, which has a density less than that of water, the density of the mixture is less than that of water and the specific gravity is less than 1. If you add sugar and alcohol the sugar pulls the specific gravity up while the alcohol pulls it down. Compare to the refractometer where both alcohol and sugar increase the refractive index of the mix. Tables of density vs concentration and density vs refractive index are available for binary mixtures of sucrose and water and ethanol and water. But been isn't a binary mixture nor, indeed, a ternary one. But it behaves, with respect to density like a ternary mixture so that reasonable alcohol estimates can be made from hydrometer readings. The same cannot be said for refractive index.

 

[LuiInIdaho]

I ask this because I have started to use a mash correction factor of 1.4 and I suspect something is wrong. A definitive list of 15 BRIX to 3 BRIX in 0.1 BRIX steps would be very helpful. All of us could check our calculations against it.

Also, how do you calculate ABV ?

thanks

I use Brew Math on my iPhone. It does Brix conversions, gravity corrections, ABV Calculations and a lot more. If you have a smart phone there are a lot of apps available for free or a small fee.

Mark

 

[bobtheUKbrewer2]

ajdelange - thanks again - I am getting closer to understanding now. In future I shall use my BRIX readings from my refractometer as " comparators" from one brew to the next. So a 10 BRIX og and a 5 BRIX fg will be weaker than a 11 BRIX og and 4.5 BRIX fg. So my FINAL (promise) question is - how best to ESTIMATE ABV from refractometer readings.

 

[azeeb]

This calculator is as good as any for estimating.

http://seanterrill.com/2012/01/06/refractometer-calculator/

I use it, and while it may not be 100% accurate, I care more about how my beer tastes then what the FG or ABV is.