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Old 09-19-2011, 10:50 AM   #1
bushwilliams
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Okay, so here is the question, likely answer is simple. I take a reading, say of my OG. The reading may be 1055 however if I set down the refractometer and forget about it for an hour it may have crept up to 1065. Is this normal? My gut (and expected numbers) tells me the initial 1055 is the correct choice, but then why would it float like that? Is the ATC (I have ATC) just getting wonky as the bead sits on the glass? Your thoughts are as always, appreciated.

Note (ATC Refractometer, calibrated with RO/DI to 0.00 on each brew day)samples in question are pulled from 150-170 degrees and read immediately. When allowed to cool they are increasing.


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Old 09-19-2011, 11:28 AM   #2
fxdrider
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I'm just guessing here, but maybe evaporation of some liquid may leave a slightly denser wort sample. Again, just a guess - I may be WAY off.


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Old 09-19-2011, 01:24 PM   #3
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I too would guess evaporation is the culprit

 
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Old 09-19-2011, 02:27 PM   #4
bushwilliams
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Hmm that makes a little too much sense now that you lay it out there. This is good, my gut told me those initial numbers were right (especially since they are usually the ones I am trying so hard to hit) thanks for your input, its great to have faith in my gear.
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Old 09-19-2011, 06:48 PM   #5
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Might also check the instructions. I believe most ATC's on refractometers have a range where the ATC works.

 
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Old 11-20-2011, 02:56 AM   #6
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I just did a brew the other day. Took OG reading right away w/hot wort and got a readding of something like 14 brix. Waiting about 1 min I get a reading about 20 brix. Never thought about evaporation. I've been using the higher number because I figure that the hot wort has to cool a bit. I'll never have wort at 60* which I understand is what the meters are calibrated for.
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Old 11-20-2011, 02:15 PM   #7
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Quote:
Originally Posted by C-Rider View Post
I just did a brew the other day. Took OG reading right away w/hot wort and got a readding of something like 14 brix. Waiting about 1 min I get a reading about 20 brix. Never thought about evaporation. I've been using the higher number because I figure that the hot wort has to cool a bit. I'll never have wort at 60* which I understand is what the meters are calibrated for.
What? Don't you have refrigeration in Hawaii? Take a small sample in a metal measuring cup and set it on a cube of ice or in a small container of ice water. You can cool it quite quickly that way. Be sure to have a thermometer so you can take it off the ice when it gets to 60.

 
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Old 11-20-2011, 02:28 PM   #8
bpolivka
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Also, ATC compensates for the temperature of the refractometer, not the sample. You don't need to wait long for the few necessary drops to cool, but you will get a low reading if you try to measure a hot sample right away.

 
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Old 11-21-2011, 01:51 AM   #9
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Quote:
Originally Posted by bpolivka View Post
Also, ATC compensates for the temperature of the refractometer, not the sample. You don't need to wait long for the few necessary drops to cool, but you will get a low reading if you try to measure a hot sample right away.
Very interesting! I thought ATC was for the sample, not the temp of the refractometer. How long would it take for a drop of wort to cool? I'm guessing not too long.

 
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Old 11-21-2011, 01:59 AM   #10
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Quote:
Originally Posted by bpolivka View Post
Also, ATC compensates for the temperature of the refractometer, not the sample. You don't need to wait long for the few necessary drops to cool, but you will get a low reading if you try to measure a hot sample right away.
Really? I take a sample and look at it then write down the gravity, Then I look again and write down the brix. During this time nothing changes. I wipe the lens clean and take another sample. I have not seen any changes. I have even waited a few minutes and looked again and it is still the same. I don't know what I am doing wrong/right.



 
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