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Brix Calculation

edited August 2016 in General

I have been working on my spreadsheets and have reached a confusing cross road intersection regarding Brix calculation. This because there seems to be more than one way of calculating it with a resulting different answer.

Method 1. ......... Answer on the right
Calculating °Brix from SG is based on an expression from a polynomial fit to a large data set:

brix = 143.254 * sg3 - 648.670 * sg2 + 1125.805 * sg - 620.389

Method 2. ............Answer on the left

Brix = (((182.4601 * SG -775.6821) * SG +1262.7794) * SG -669.5622)

The error is in the decimals, though it may appear insignificant it has implications in other calculations which are derived from the Brix answer.

5 SG conversion
     SG                    1.1
     Brix                  23.7741921   23.776874
     Plato                              23.768887
     Oechsle                            100
     Baume                              13.18181818
     Babo / KMW                         20.16818182
     grams / liter                      1100
     Dissolved solids g/l               261.545614

     DSOS                               0.007
     EstSG                              1
     PA  % ABV                          12.56544503

As the SG increases so the error is more noticeable

5 SG conversion
     SG                    1.355
     Brix                  71.25892776  70.4917271
     Plato                              69.86677476
     Oechsle                            355
     Baume                              37.98892989
     Babo / KMW                         58.12306273
     grams / liter                      1355
     Dissolved solids g/l               955.1629022

     DSOS                               0.007
     EstSG                              1
     PA  % ABV                          53.99534523

Any better more definitive answer ????


  • Solution = buy a refractometer.

    I'm more like I am now than I was before.

  • edited August 2016

    The formula I have often seen is the other way around ie calculating SG from Brix ie to give you a reading following a refractometer measurement

    This site has the following formula:

    Specific Gravity From Brix =  (1 / (1 - (brix / 261.3))

    I am curious about what it is you are trying to calculate / solve by doing these equations.

    Your 2 examples are at SG of 1.1 and SG of 1.355. What are you trying to ferment? They are both strong sugar concentrations - the 2nd, ridiculously so. A typical distilling wash will have an SG of around 1.080 to produce 8-10% abv. Part of the reason for doing so is to NOT stress our yeast. I don't know of any yeast that would cope with that - even industrial fuel yeasts crap out around 25% alcohol.

    I believe that in many things, you will rarely hit your numbers - use recipe formulations as a guide - take measurements and record them. over time you will see patterns / consistency emerge if you stick to the same recipe / ingredients / process.

    Remember, in theory there is no difference between theory and practice. However in practice, there is.

    Hope that helps.

  • edited August 2016

    Correct, the one is a ridiculous value for fermentation. But I am trying to get the values correct for my model.

    To put into perspective, I will be diluting apple concentrate from 70 Bx down to 24 Bx. This is to make a new cheap recipe for our apple cider. Also to then possibly also distil this fermentation as a second option.

    See below

    Concentrate dilution                          
    Starting Brix             70
    SG at start               1.352784843
    Dissolved solids g/l TSS  946.9493899
    Ending Brix               24
    SG at end                 1.101020352
    Dissolved solids g/l TSS  264.2448846
    1 Liter of AJC weighs @  Bx     70     1.352784843 kg
      Of which is sugar   %         70     0.946900000 kg
      At 24 Bx the same amount of sugar will be present, thus
      The diluted solution will be         3.945600000 kg
      Convert to volume                    3.583600000 liters
      So volume of water to add            2.583600000 liters
    OR if you use the TSS ratios
    1 Liter of AJC converts from/to 70 24  3.583600000 liters
      Thus volume of water to add:         2.583600000 liters
  • edited August 2016

    Maybe Jan van de Snepscheut can help you write your spreadsheet... ;;)

    I'm more like I am now than I was before.

    I'm more like I am now than I was before.

  • edited August 2016

    Level of error seems insignificant, especially trying to do dilution at large scale. I would imagine this would likely be at or near the resolution of your scale. Assuming also,that while you show liters here, that you are really talking about dilution by weight - otherwise you would need temperature compensation on both sides, no?

    Also, converting to BRIX, isn't there going to be error because of the glucose and fructose in Apple Juice? As opposed to a pure sucrose solution? Wouldn't there need to be a correction factor for apple juice vs equivalent sucrose brix? If it's input to potential alcohol, that too is fraught with error.

    Too early and not enough coffee yet.

  • Yes dilution by weight and then converted to Litres.

  • What are you trying to hit and/or measure?

    If you have juice at a determined brix, then can't you measure and dilute by weight? When I'm making my sugar washes, I'm measuring mass, calculate sugar and dilute to desired Brix/Plato/SG

  • 2.5 gal water per 1 gal of concentrate to go from 70(1.355) to 24(1.101sg), according to the long standing honey.xls spreadsheet from hightest's honey haven....

  • When measuring the brix of my molasses washes I have always wondered just how accurate my refractometer is since the molasses has so much solids in it. Or what corrections I have to make to the reading since I don't know the original brix number before dilution.

  • i dont believe they are accurate at all in this application. Too much effect from solids and other dissolved components. will be interesting to see other responses.

  • edited August 2016

    Perhaps this doesn't pertain to the mainstream of this thread, but it does pertain to FC's question. Brix-to-SG (or vice versa) conversion can only be accurate with binary sucrose-water solutions, although it's probably helpful with othersugar-water solutions, when reading Brix with a refractometer.

    If this seems like picking nits, note that for many fermentations, as the SG approaches 1.000, the SG, as measured by the hydrometer, does not approach 0, at least not with some of the ferments I run. I'm pretty sure that the reason for this disparity is at least partially because the solution is no longer even close to binary, notably with the presence of ethanol.

    It's important to note that the refractometer measures index of refraction, and the hydrometer measures density, and neither one of them knows shit about sugar concentration in the absence of further information (like exactly what's in that solution.

    Zymurgy Bob, a simple potstiller

    my book, Making Fine Spirits

  • The numbers don't mean much with the refract but as long as they're consistent it wont mater too much.
    They're astronomically inaccurate but extremely precise if that makes sense. They're very quick and easy but you just need to know where your targets are on a meaningless scale.
    I stuffed around with it a while back.

  • I reckon Grim, Cotherman & ZB are on the right track. The degree of accuracy isn't critical.

    Use a dilution calculator to determine how many litres of water you need to cut back from 70brix to 40 brix. As 1l of water = 1kg, you know the weight of water to add. Simple.

    In Ray Daniels excellent book Designing Great Beers, dilution/gravity calculations are based on this simple formula:

    Beginning Volume * Beginning Gravity=End Volume * End Gravity

    It is easy enough to rearrange this to get your end volume. Then a subtraction will give you the water addition required....

  • According to my beginning SG minus ending SG I am getting 6.5%-7.5% ABV which is a good target for rum. I have also used beginning and ending numbers on the refractometer the same way to calculate ABV so I'm not quite sure why I bought the refractometer, at least for rum washes.

  • So you don't have the same issue as in my link?

  • Yes, I just didn't see the link. Same exact issues. I too felt like my washes weren't fully fermented out but in hindsight they probably were. My last one started at 1.095 and is finished at 1.037 according to my hydrometer.

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