Measuring OG with Refractometer

Discussion in 'Beginners Brewing Forum' started by Mark Watson, Mar 10, 2019.

  1. Mark Watson

    Mark Watson New Member

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    Hi Everyone. I'm reasonably new to home brewing and am gradually increasing my knowledge and trying to upgrade my techniques. I would like to have a far quicker way of measuring pre-boil SG and I bought a refractometer and have now calculated the 'Wort Corrective Factor' as 1.0229 from measuring 5 different worts 5 times with it and my hydrometer (as per instructions on various sites). However, I'm not quite sure what I do with the 'Correction Factor'! I assume that I read the BRIX on the refractometer then divide (or multiply?) it by the 'Correction Factor' to give me a corrected Brix reading then convert Brix to SG? Can anyone help? Many thanks. Mark
     
  2. Nosybear

    Nosybear Well-Known Member

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    Sounds like you have it figured out. Read the Brix, multiply by the wort correction factor, then convert to SG.
     
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  3. Mark Farrall

    Mark Farrall Well-Known Member

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    You can also add it into the equipment profile here so that if you're using the brew sessions feature it will apply the correction factor for you (haven't tried that myself).
     
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  4. Craigerrr

    Craigerrr Well-Known Member

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    To the best of my knowledge, my refractometer gives me a straight up gravity reading... I haven't been doing any corrections to the readings.
     
  5. Nosybear

    Nosybear Well-Known Member

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    I use it throughout fermentation - far lower samples, I can keep track of how things are going and with the correction, it's as accurate as my hydrometer. Far easier to read, too.
     
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  6. Mark Watson

    Mark Watson New Member

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    Thanks for this. So I multiply rather than divide the BRIX reading by the correction factor yes? Much appreciated
     
  7. Yooper

    Yooper Administrator
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    Yes, for a super quick estimate on the fly, just multiply by four. If the refractometer has 14.8, the estimated brix is 59 (1.0592). Then, when you have a moment, use the calculator with the correction factor in it:
    https://www.brewersfriend.com/refractometer-calculator/
    upload_2019-3-11_8-58-36.png

    For info:
    https://www.brewersfriend.com/2013/...rrectly-for-maximum-accuracy-in-home-brewing/
     
  8. Craigerrr

    Craigerrr Well-Known Member

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    my refractometer has an SG scale on it, do I need to make any corrections?
    Maybe next brew Iwill do both and confirm the readings
     
  9. Nosybear

    Nosybear Well-Known Member

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    You won't need to correct if your refractometer already has an SG scale. If it is in Brix, it's a wine refractometer and you need the corrections. If it's in SG, it's made for beer and the scale is already corrected. I use the correction factor in the equations to convert from SG to Plato when I'm correcting the beer for alcohol as well.
     
  10. 716Brewer

    716Brewer New Member

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    I thought the refractometer becomes inaccurate once there is alcohol present?
     
  11. Mase

    Mase Well-Known Member

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    It does, that’s why you use the correction factor.
     
  12. Nosybear

    Nosybear Well-Known Member

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    There are equations you can use to correct it. This site has a calculator that employs one: You enter the original gravity and the refractometer reading, as well as your refractometer correction factor, and it converts the reading to SG, You're right that the actual reading is inaccurate but it can be corrected. The correction equations used here and in a past issue of Zymurgy are accurate on FG to the point where I can't tell the difference at 3 decimal points between my finishing hydrometer and my refractometer.
     
  13. 716Brewer

    716Brewer New Member

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    I gotcha now. I thought it was like a calibration to ensure overall accuracy. Thanks for the clarification.
     
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  14. thunderwagn

    thunderwagn Well-Known Member

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    I realize this is an older post, but I just purchased my refractometer and had the same question. If I'm understanding the information presented on this site correctly, I shouldn't go off the SG scale.
    https://www.brewersfriend.com/2013/...rrectly-for-maximum-accuracy-in-home-brewing/
    Have you found out differently? A bit confused now.
     
  15. Mark Farrall

    Mark Farrall Well-Known Member

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    Theory is that the SG scale should be ignored because brix is based on only sucrose in water. The mix of sugars we have in beer needs a slight conversion from brix to SG to account for that different sugar profile.

    I've no idea how much of a difference it makes in practice. I use the brew day feature here and that's got the brix to SG converter built in so I use that and don't even look at the SG scale. I imagine if I paid attention it might turn out to be the difference between how strong the light source is or not. And I suppose if you trust your manufacturer they may have that conversion built into their SG scale.
     
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  16. Nosybear

    Nosybear Well-Known Member

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    The calculator on this site will convert SG (read) to SG (Actual). It's the difference between measuring in inches or centimeters, you're measuring effectively the same thing just using a different ruler. Brix assumes all the difference in density of the solution is sucrose, SG doesn't care what's causing it, both work equally well. You will have to determine a wort correction factor by reading your hydrometer and your refractometer but it should be about 1.04. I use SG exclusively, not right or wrong. Brewers use degrees Plato, effectively the same as Brix.... Use what you're comfortable with, either scale works fine.
     
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  17. thunderwagn

    thunderwagn Well-Known Member

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    Thanks for the explanations. I should have read up a little bit before I jumped right in. I use different refractometers everyday for reading propylene glycol levels in heating and chilled/chiller systems and just assumed the reading was what it was. The difference in brix vs sg wasn't great, but it was a couple of points when converted. It did put my numbers right on track when I back tracked my sg reading to brix. However, I didn't even think to use my new hydrometer to compare. Again, I'm close enough and not real concerned. Just making sure from now on I'm on the 'right' track. At least now I feel like I have the knowledge to proceed on.
     
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  18. Mark Farrall

    Mark Farrall Well-Known Member

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    Ha, got the conversion factor pointing at the wrong thing. Thanks for the clarification.
     
  19. Craigerrr

    Craigerrr Well-Known Member

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    My refractometer only has the SG scale (it was a gift from my daughter), I have just assumed the reading is the reading. I have found that my numbers typically line up to expectations (unless I eff something up like on my last brew). I love it because I can quickly check gravity all throughout brew day. Specifically, on my last brew I knew I had an issue when I checked the gravity of my first runnings (thank the sweet baby Jesus that I had DME on hand!)
     
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  20. Hawkbox

    Hawkbox Well-Known Member

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    I use SG cause that is what I started with. It's close enough for the girls i go with.
     

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