Refractometer reading

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goswell

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I've got a refractometer that I will occasionally use and I'm curious what others find when comparing the refractometer to a hydrometer. When I take a refractometer reading, it will usually be spot on with the hydrometer using the simple conversion method. That's all fine and good but everything I've read says you need to use a refractometer correction value of about 1.04 to get it to accurately match the hyrdometer reading. Doing that causes them to not match up anymore?
Example:
Refractometer reading: 16B
Hyrdrometer reading: 1.065
Using a simple conversion formula to convert brix to sg:
((16-1.6)/220)+1 = 1.065 (perfect)

If I take my refractometer reading minus the correction factor:
Refractometer: 16 - 1.04 = 14.9
Using the same formula to convert:
((14.96-1.6)/220)+1 = 1.060 (Now 5 points off)

What gives?



Now it's 5 gravity points off?
 
First off, have you calibrate both the hydrometer and refractometer with distilled water? The refractometer calibration should be done each day it's being used, as ambient temperature effects this.
 
Factor means multiply, not subtract. However, formulas are pretty much extra work in this case because multiplying brix by 4 is close enough. 20 brix x 4 = 1.080 SG.

The times 4 method IS close enough when converting Brix to SG, it's the method of getting that Brix reading that changes things, the method I'm speaking of is using a refractometer:

Brix refractometers are meant to measure the percentage of sugar in a pure sucrose solution. Since wort is not simply sugar and water, you need to make a small correction because of the non-sugar components of the wort.
To calculate your correction value, measure the specific gravity with your refractometer. Then chill a sample of your wort and measure the gravity with a hydrometer. Convert the hydrometer reading to Brix using the equation: Brix = (SG-1)/0.004. Then divide the reading of the refractometer by your actual hydrometer reading. You should have a number between 1.02 and 1.06.
 
Yeah, but the multiply by four rule of thumb is already taking the wort correction factor of 1.04 into account. If you read 20 brix, it's "about" 1.080 SG. That isn't true for sucrose water which would be closer to 1.084.
 
Has anyone used the Refractometer that displays Brix and SG?
Also, I was curious about the ATC (automatic temperature compensation) in relation to the conversion.
I just purchased this one from AHB. Hopefully it will be here by Monday and I hope to brew one day this week.
 
My correction factor, with my refractomer, is 1.0344. I use Beersmith to figure exact readings, but I'm the one who actually "told" Beersmith which correction factor to use. I did it by taking multiple readings, with a hydrometer and refractometer and that's the number I needed for a correction factor. Now, it's spot on.

Maybe your correction factor isn't a standard 1.04? In fact, mine is close to that, but I would bet that most people would find variations. That's why you find your "own" correction factor.
 
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