Refractometer Calibration

[AndrewQLD]

At Batz's brewday I brought up the subject of refrac usage, the main problem I have is getting my refrac to agree with my Hydrometer, the sg never seems to agree with my brix reading. Using Beersmith there is a refrac calibration tool. But it seems from one brew to the next the readings can vary. Does anyone else have this problem. Below is an extract from a BYO Article explaining what I am trying to say :blink: .
What does everyone do regarding their refrac, do you just take a reading and convert to sg or do you compensate for the fact that you are testing wort rather than sugar.

Andrew

Extract below taken from the BYO site.
Wort Calibration

Measurements of the specific gravity of wort using a refractometer will not agree with the measurements of gravity using a hydrometer. 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. The correction factor is different for different breweries. Beers that are very dark or have a very high starting gravity may also require a different correction factor. 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. If you do this for several worts and average them, you will get a number that you can use for your brewery. ProMash defaults to 1.04 and this is the number I use. Once you have this number, divide all of your subsequent refractometer readings by your calibration number to get the actual reading. For example, if your reading is 14.6 Brix then your corrected reading is 14.04 Brix (14.6/1.04=14.04). Then, we can convert the measurement in Brix to specific gravity.

Once youve calibrated your refractometer and measured your wort correction factor, you can obtain a measurement of your specific gravity quickly, without having to cool enough wort for a hydrometer sample. You can use the refractometer to measure the gravity of your wort during run-off to help you to decide when to stop sparging. Likewise, you can quickly obtain your gravity anytime during the boil to determine if you need to keep boiling your barleywine or if adding water to your best bitter is in order.

 

[warrenlw63]

I just go by the ProMash Brix correction factor of 1.040.

Refractometer and Hydrometer end up reading the same.

Warren -

 

[bradmcm]

Yep, I use the same figure as Warren.
I've tested my cheap Chinese made refractometer against professional brewing hydrometers (not the cheap homebrew ones) and found it to be spot on.

Andrew, I assume you have calibrated the zero point with distilled water at 20C?

 

[Darren]

Andrew,
It is VERY important to clean and dry the refractomenter between readings. As it only uses small volumes, any amounts of water or sugar remaining between tests will skew the readings.

 

[AndrewQLD]

I will calibrate to 1.040 and see how this goes. I have calibrated with distilled water and I am very careful about keeping it dry and clean.

Cheers
Andrew

 

[PeterS]

I will calibrate to 1.040 and see how this goes. I have calibrated with distilled water and I am very careful about keeping it dry and clean.

Cheers
Andrew

[post="68843"][/post]​

Andrew, this calibrating to 1.040 confuses me a bit.

I have no idea if this is the correct way to do it or not (only used it with 3 brews) but what I did was to use distilled water for the first time (at 20C) and I moved the adjusting screw up or down until I read zero on the brix scale. BeerSmith tells me that my subsequent correction factor will be 1.0009. In any case this correction factor is automatically taken into consideration by BeerSmith and I have found so far that my Brix reading conversion equals my Hydrometer reading exactly.

Clear as mud?

:beer:
PeterS....