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Refractometer calibration

So I broke down and bought a refractometer (this one http://www.northernbrewer.com/shop/brix … h-atc.html)

Instructions came with it on how to calibrate it. They also said to recalibrate if your temperature differs from 5 degrees of the temp which you calibrated it at. I brew in a cold garage in the winter (can be as cold as 15 degrees). Do I really need to calibrate this thing while out there or will the temp swings not matter that much?

From the page you referenced:

“Our refractometers measure from 0-32° Brix, with an accuracy of +/- 0.2° Brix. They also include automatic temperature compensation for temperatures between 50-86° F, which eliminates the need to consult temperature correction charts.”

So if you stay within those limits, I’d say you don’t need to recalibrate. If you are outside that, I’d use the temperature compensation charts rather than recalibrate.

I got inconsistent results from my refractometer until I read (Denny’s post) that the ATC automatically corrects for the temperature of the refractometer, not for the temperature of the sample. Now I dip a tiny sample of wort with a thick-wall glass, tip that into another thick-wall glass, and finally drip that onto the refractometer glass. My results now are accurate and quick.

Read the sample quickly after dripping it onto the refractometer. If you let it sit for a few minutes the gravity reading will increase, apparently due to evaporation.

Your arctic conditions may make all of the above moot. You may need to consider moving to Florida.

That is a horrible idea. Then you’d need to deal with warm water when you’re trying to chill, and having to actively cool to keep your fermentation temperatures in check.

[quote=“rebuiltcellars”]From the page you referenced:

“Our refractometers measure from 0-32° Brix, with an accuracy of +/- 0.2° Brix. They also include automatic temperature compensation for temperatures between 50-86° F, which eliminates the need to consult temperature correction charts.”

So if you stay within those limits, I’d say you don’t need to recalibrate. If you are outside that, I’d use the temperature compensation charts rather than recalibrate.[/quote]

I wish I would have known this when I bought it. I guess it’s my fault for not doing to research. The reason I bought it was for convenience but it’s appearing that if I have to either compensate with a chart for correction or go inside the house to take the reading it’s more of a pain that anything else. Buyers remorse is now setting in.

Make a calibration solution per the following article:

http://byo.com/stories/issue/item/411-calibrate-your-hydrometer-and-fermenter-techniques

Use this solution to calibrate both your hydrometer and refractometer at your point of use and inside your house at normal room temperature to develop a correlation chart.

[quote=“Ken in MN”]Make a calibration solution per the following article:

http://byo.com/stories/issue/item/411-calibrate-your-hydrometer-and-fermenter-techniques

Use this solution to calibrate both your hydrometer and refractometer at your point of use and inside your house at normal room temperature to develop a correlation chart.[/quote]

But is the difference due to changes in temperature linear with respect to F for a refractometer and differing sugar solutuions? Say the calibration solution reads 1.000 at 68F and reads 1.005 at 35*. Can I say that my sugar solution will also be 5 points off? It makes sense for a hydrometer cause gravity remains constant over changing temperature but does the refraction of light through a sugar solution change based on ambient temps? It may not, just don’t really know the science behind it.

Maybe, but only you can determine through experimentation whether or not it makes any difference. Check it while out in the cold, then check it again while in a room at normal room temperature and see how far off it is. If it’s off, then determine whether or not it is far enough off to worry about. If it is, then check it at several more ambient temperatures in between winter and spring and then plot the results on a graph. From there you should be able to determine a correlation and whether or not that correlation is linear. Excel is good for line fitting and correlation curve type determinations. Here is some more information on using refractometers:

[quote=“Ken in MN”]Maybe, but only you can determine through experimentation whether or not it makes any difference. Check it while out in the cold, then check it again while in a room at normal room temperature and see how far off it is. If it’s off, then determine whether or not it is far enough off to worry about. If it is, then check it at several more ambient temperatures in between winter and spring and then plot the results on a graph. From there you should be able to determine a correlation and whether or not that correlation is linear. Excel is good for line fitting and correlation curve type determinations. Here is some more information on using refractometers:

[/quote]

Yeah my concern is the differences not only between temps but also different gravities. Testing all sorts of temps and gravities sounds more like an experiment id rather have someone else do and report their findings to me :slight_smile:

It’s still fairly simple; you could do a three point calibration at each temperature. Make an additional calibration solution that is a higher specific gravity, such as 1.080. Dissolve 40 g of sucrose in 160 g of distilled water to make a 1.080 solution. While a 1.040 solution (20 g of sucrose in 180 g of distilled water) will equal 10 degrees Plato, the relationship between SG and degrees Plato is less linear the further away from 1.040 you go, so that a 1.080 SG solution is not 20 degrees Plato but rather approximately 19 degrees Plato. See here:

You certainly could wait for somebody else to do the work, but the results most relevant to your brewing situation would be your own. I would do it myself, but the extent of my outdoor brewing is limited to only having to do the boiling on my deck, with the burner conveniently located right outside my kitchen’s patio door. All of the other work is done in my kitchen, so no cold garage for me! Therefore, all of my refractometer measurements are done inside my house at typical room temperature.

Yeah, I’m sure I’ll find something that works for me. It could be as simple as leaving the refractometer just inside the house till i need it.

That is a horrible idea. Then you’d need to deal with warm water when you’re trying to chill, and having to actively cool to keep your fermentation temperatures in check.[/quote]

I’ve only been to Finnland in the winter (early January and late June), so I can see that it would be a lot easier to chill wort and ferment cool. But, don’t you have to heat the fermenter unless your doing all your lager fermentations during July?

That is a horrible idea. Then you’d need to deal with warm water when you’re trying to chill, and having to actively cool to keep your fermentation temperatures in check.[/quote]

I’ve only been to Finnland in the winter (early January and late June), so I can see that it would be a lot easier to chill wort and ferment cool. But, don’t you have to heat the fermenter unless your doing all your lager fermentations during July?[/quote]

You should try to visit in the summer. The Finnish summer is very beautiful. Short but very very beautiful. Last year it happened on a Tuesday.

The houses here a too well insulated and kept too warm to ferment inside, so I built a Styrofoam fermentation chamber in my outside shed, which allows me to do precisely controlled fermentations 9 months a year only using heat. That leaves a couple months (mid June to mid August) where it is generally too warm to make beer without active cooling, so I take off then.

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