Refratometer inconsistenty

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Driddy

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I'll keep my question simple because I have tried to be technical regarding my frustration with my refractometer.

Why does my reading change with the temperature of the sample?

I have a ATC Refractometer. If I understand this correctly, it automatically adjusts for the temperature of the refractometer, not necessarily for the sample. The sample adjusts over a few moments to the temp of the refractometer because the volume of the sample is so small.

So riddle me this......A 1 oz. sample of wort is taken form the kettle after run-off. Sits on the counter for several minutes while doing other things. Reduces in temp to somewhere in the neighbor hood of 120 Deg. Take several readings with the meter. Each one comes in @ 14.6. Just for kicks, I heat the 1 oz. sample up in the microwave to close to 200 Deg. to see if that changes it. I take several more readings......16.2!!!! That's is a big difference. I am really getting frustrated. Can some one PLEASE help figure this out. Is it my technique or is it my refractometer? Any insight might prevent me from throwing this "helpful" tool into my neighbors fence!

Riddy
 
Driddy said:
I'll keep my question simple because I have tried to be technical regarding my frustration with my refractometer.

Why does my reading change with the temperature of the sample?

I have a ATC Refractometer. If I understand this correctly, it automatically adjusts for the temperature of the refractometer, not necessarily for the sample. The sample adjusts over a few moments to the temp of the refractometer because the volume of the sample is so small.

So riddle me this......A 1 oz. sample of wort is taken form the kettle after run-off. Sits on the counter for several minutes while doing other things. Reduces in temp to somewhere in the neighbor hood of 120 Deg. Take several readings with the meter. Each one comes in @ 14.6. Just for kicks, I heat the 1 oz. sample up in the microwave to close to 200 Deg. to see if that changes it. I take several more readings......16.2!!!! That's is a big difference. I am really getting frustrated. Can some one PLEASE help figure this out. Is it my technique or is it my refractometer? Any insight might prevent me from throwing this "helpful" tool into my neighbors fence!

Riddy
Click to expand...

You are heating a 1 ounce sample in the microwave? And you went from 1.057 to 1.064 SG? That's equal to a loss 11% volume...are you sure you didn't just lose 3 or 4 mL due to steam/evaporation while you nuked it and while it sat on the counter?
 
10 - 30 C of the sample or the environment/refractometer. If it is the sample, then how are able to take a sample from the boil kettle to check gravity?

If I have to cool a sample, then I may as well use a hydrometer? Do I understand this correctly?
 
Driddy said:
10 - 30 C of the sample or the environment/refractometer. If it is the sample, then how are able to take a sample from the boil kettle to check gravity?

If I have to cool a sample, then I may as well use a hydrometer? Do I understand this correctly?
Click to expand...

#1) You need to check the ATC range of YOUR refractometer
#2) If you take a small sample (I have 10ml pyrex pipette) in the 1-2ml range and just hold it out of the brew kettle for 10-20 seconds before measuring, I usually get a pretty accurate read.


However, I do find shorty's explanation to be more probable.
 
Hmmm... Maybe this explains why my refract readings started at 17 Brix pre boil, and ended at 15.5 Brix post boil last weekend...
 
Driddy said:
10 - 30 C of the sample or the environment/refractometer. If it is the sample, then how are able to take a sample from the boil kettle to check gravity?

If I have to cool a sample, then I may as well use a hydrometer? Do I understand this correctly?
Click to expand...

you don't need to cool the sample that tiny amount will come to the temp of the refractometer. You have to have the refractometer in the correct range to get a accurate reading. Lets say you calibrate your refractometer in the house @70° thats within the range now you go outside do your brew take your reading after your boil but its 35°and the refractometer is at ambient your readings will way off
 
Yes
Heat mass of the refractometer is HUGE and your sample is very small it will equilibrate to the same temp (within measurable error) weather you take it at 0 or 100 degrees - but give it say 10 seconds to thermally "relax" on the reading glass.
I also would guess your funny readings are a result of evaporation.
PS. zero your refractometer just before you take the reading each time (if you brought it into a warm room from a cold storage cabinet for example)
 
giligson said:
Yes
Heat mass of the refractometer is HUGE and your sample is very small it will equilibrate to the same temp (within measurable error) weather you take it at 0 or 100 degrees - but give it say 10 seconds to thermally "relax" on the reading glass.
I also would guess your funny readings are a result of evaporation.
PS. zero your refractometer just before you take the reading each time (if you brought it into a warm room from a cold storage cabinet for example)
Click to expand...

what he said +1
 
Randar said:
Which explanation? Temp or evaporation?
Click to expand...

Temp. I was brewing outside on my patio in 18*F weather. My refractometer kept giving me crazy readings, and I just didn't think about the temp calibration issue.
 
Munsoned said:
Temp. I was brewing outside on my patio in 18*F weather. My refractometer kept giving me crazy readings, and I just didn't think about the temp calibration issue.
Click to expand...

I leave the refractometer in the house during cold weather brewing. And bring the sample to it.
 
Well after experimenting ALL morning.....I guess that I have to take a sample in a pipette and let it's temperature drop to within the range of the refractometer before I place the sample on the sight glass. I have been able to get, at the very least, more consistent readings. I have had in the past, considerable differences in my hydrometer reading and my refractometer. This however, may have been due to my technique that I have been struggling with. Am I making something simple more difficult than it has to be?
 
One more thing - just to be clear - with a refractometer you must COMPLETELY clean the sample glass and cover and you must COMPLETELY dry the glass and cover before taking a reading - because the size of the sample is so small even a small amount of carryover of dried on sugar (malt, etc) or dilution from carryover of rinse water will adversely affect the precision of your readings.
 
I was screwing with my refrac one night while my brother and I were drunk and drinking grappa. In my drunken stupor I decided to put two drops of grappa on the lense to see what it measured at. Each time I lifted the cover and put it back down the reading dropped. Thank god my brother was more sober than I at the time because I was CONFUSED. However with our powers combined I realized that the ethanol in the grappa was evaporating (very rapidly I might add) at each cover lift giving me a lower reading, I forgot that it measured ethanol along with sugars at the time.
 
I do clean the lens before taking another reading. A relatively quick rinse with cool water and a dry with paper towel. Is that enough? I do make sure that the lens is dry. It seems as though my problem is when taking the sample out of the BK. after my brew was finished. I played around with the 1 oz sample from the brew,now at room temp, I seem to get a more consistant reading. I guess I was just suprised (an frustrated!) by the affect Temperature had on the sample....for what ever reason, evaporation or otherwise.
 
Your refractometer readings are NOT going to match up to your hydrometer readings for every batch, unless you are brewing the same beer every time.
 
springer said:
you don't need to cool the sample that tiny amount will come to the temp of the refractometer. You have to have the refractometer in the correct range to get a accurate reading. Lets say you calibrate your refractometer in the house @70° thats within the range now you go outside do your brew take your reading after your boil but its 35°and the refractometer is at ambient your readings will way off
Click to expand...

This sounds like the way I understood it....

weirdboy said:
Your refractometer readings are NOT going to match up to your hydrometer readings for every batch.
Click to expand...


And this is what I thought this thread was about reading the title. Is it time for a hijack yet? Can I take this :off: ?
 
Sure.....Hijack a away! I think the answer I'm looking for will eventually be found. "Buy a RELLY ExPENSIVE" digital refractometer! Do you think SWMBO will understand?
 

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