Should I trust my refractometer, or my hydrometer?

I usually only use my refractometer while sparging to make sure I don't overdo it. On a lark, I decided to check my OG with it, along with my hydrometer. My refractometer read 12.9 brix (1.052 sg), while my hydro read 1.057. I know it's not a huge difference, but I think it's noteworthy. Which one should I trust?

I posted this very same question (idea) a while back. My question centered on the "correction factor" when getting the brix reading from a refractometer. If you include the correction factor, you get your 1.052 reading, but if you just do the "times 4" method, you get 1.051.6 (1.052). So, the answer I'll give you, and what I've started doing is just using the "times 4" method because doing that, the hyrdo and the refrac always come out the same. That whole refractometer correction value is a bit of a mystery to me?

Both. Make sure both are calibrated, and then make sure they are calibrated to each other. You should be dead-nuts on both. If it is an ATC refractometer, make sure it is calibrated at the ambient temperature stated in the instructions. Also make sure that you're using it within the range of ambient temperatures stated, usually from 53F-86F. Same with hydro, the farther you get from the calibration temperature, the more the variability.

Reelale said:

Both. Make sure both are calibrated, and then make sure they are calibrated to each other. You should be dead-nuts on both. If it is an ATC refractometer, make sure it is calibrated at the ambient temperature stated in the instructions. Also make sure that you're using it within the range of ambient temperatures stated, usually from 53F-86F. Same with hydro, the farther you get from the calibration temperature, the more the variability.

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I regularly check the calibration of both. The refractometer, I check the calibration every brew day, and the hydro, almost every brew day. That's part of my confusion. They read the same "zero" point, but not higher. This is the first time I've used them for an actual reading side-by-side, but I checked and re-checked since the results varied, and they were solid, 12.9 and 1.057.

If it is an ATC, you shouldn't calibrate it every brew day. It has a very tight calibration requirement. Mine is 68 degrees. Once I calibrate it at that temperature, it's good within the range of 53-86. I can't use it outside that range. Calibrating it temperatures outside the calibration range causes all sorts of variability.

I just did this before work this morning. I had to wait until morning for the temperature to go down to 68. Before this, I calibrated it at probably 80 something and the readings were all over the place.

Reelale said:

If it is an ATC, you shouldn't calibrate it every brew day. It has a very tight calibration requirement. Mine is 68 degrees. Once I calibrate it at that temperature, it's good within the range of 53-86. I can't use it outside that range. Calibrating it temperatures outside the calibration range causes all sorts of variability.

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I'll have to address that. I've never had to actually adjust the calibration, but I always check it with distilled water. I've never paid attention to the water temp though...

curlyfat said:

I'll have to address that. I've never had to actually adjust the calibration, but I always check it with distilled water. I've never paid attention to the water temp though...

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Not the sample temp, ambient room temperature needs to be 68 F. At least for mine.

Reelale said:

Not the sample temp, ambient room temperature needs to be 68 F. At least for mine.

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Gotcha. It is usually much warmer than that, I'll have to check my documentation and calibrate properly. Why didn't I join this forum years ago? I keep learning....

curlyfat said:

Gotcha. It is usually much warmer than that, I'll have to check my documentation and calibrate properly. Why didn't I join this forum years ago? I keep learning....

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I placed mine in a screw-top jar and poked a stem thermometer through the lid. I put it in the fridge until the air inside the jar stabilized at 68F then I quickly calibrated it. If I didn't do it that way, I wouldn't be able to use it around here until probably October