Refractometer calibration temperature

[Brewmegoodbeer]

The Refractometer I just bought recommends calibrating with distilled water when the Refractometer is at 68 degrees. Anyone know how to get a refractometer to 68 degrees? room temp at best in my house is 73. I didn’t know people keep their homes at 68 degrees!

 

[GilSwillBasementBrews]

They mean temperature. °F

 

[Brewmegoodbeer]

They mean temperature. °F

Whoops I didn’t type it correctly. Just edited post

 

[GilSwillBasementBrews]

Hold it in your hands for a minute?? I would think room temp should be fairly close enough.

 

[GilSwillBasementBrews]

I believe it’s more the sample you want at 68°F

 

[IslandLizard]

73F is close enough to 68F.
Most refractometers include ATC, so when you calibrate at 0 Brix (1.000) at 73F, that is your new calibration temp. The ATC will correct up and down from there (73F), making inaccuracies due to small fluctuations within those 5-10 degrees either way very minute. Close enough for brewing, anyway. We make bigger errors than that.

 

[RPh_Guy]

Keep in mind that if you calibrate the refractometer at whatever temperature, the refractometer should be that temperature (or reasonably close) whenever you take a reading. The sample temperature is irrelevant.

 

[Vale71]

I wouldn't sweat the small difference. If the refractometer has ATC it will correct for it anyway.
What's important is the sample temperature as temperature changes the refractive index and will thus affect the reading and ATC will not compensate for that. Again don't sweat a small difference but if for some reason you keep your distilled in the fridge I would let it warm up to ambient temp first.

 

[IslandLizard]

What's important is the sample temperature as temperature changes the refractive index and will thus affect the reading and ATC will not compensate for that.

Doesn't the heat capacity of the prism/body equalize the temps of that thinly spread-out sample within seconds? ATC then correcting for the very slight overall temp increase of the entire measuring system.

The only thing you need to watch out for is that a very hot sample will partially evaporate as it is applied to the prism, inflating your reading.

 

[Vale71]

If the difference is small then probably yes, but if the sample is boiling hot or freezing cold it could take quite some time for temperature to equalize. Keep in mind also that in the short run the sample will equalize by making part of the prism either warmer or colder thus affecting its behavior and ATC certainly can't compensate for that. If you really want an accurate measurement then both instrument as well as sample should be at the exact same temperature.

 

[Brewmegoodbeer]

The refractometer that I bought from Northern Brewer states that even though it has ATC (temperature will correct when meter is not at calibration temp at a certain range) it must be calibrated at 68 deg f with distilled water. I turned my ac down to 68 downstairs for an hour while my wife was still sleeping and let meter hang out at that temp, then i calibrated it with distilled water after letting the distilled water hang out on the prism plate for about 10 mins. Didn’t think i could get closer than that. Ill be taking readings in my house at 73 deg which is in the range of the ATC. ill just have to let the solution tested equalize to the temp of refractometer for accuracy. I guess letting it sit for like 10 mins on prism before reading it is the best way to do this?