Measuring OG with Refractometer

[Mark Watson]

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

 

[Nosybear]

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

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

 

[Mark Farrall]

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).

 

[Craigerrr]

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.

 

[Nosybear]

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.

 

[Mark Watson]

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

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

 

[Yooper]

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

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/

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

 

[Craigerrr]

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

 

[Nosybear]

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

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.

 

[716Brewer]

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.

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

 

[Mase]

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

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

 

[Nosybear]

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

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.

 

[716Brewer]

There are equations you can use to correct it.

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

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

 

[thunderwagn]

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

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.

 

[Mark Farrall]

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.

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.

 

[Nosybear]

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.

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.

 

[thunderwagn]

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.

 

[Mark Farrall]

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.

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

 

[Craigerrr]

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!)

 

[Hawkbox]

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