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Refractometer Acting Up?

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bignath

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Hi brewers,

for all of the refractometer lovers...

Have been using my refractometer for the past few years as i much prefer it to the hydrometer. I don't actually own a hydro, i gave it to my mate so he could get into brewing.

When i take my readings during the boil, i place three drops on the lense, close the lid and look through it. Write down the number.

But yesterday i noticed something i hadn't spotted before. If i leave it, the number is higher than it was when i first took the reading.

Cooled sample....yeah i know, i know... BUT, if i open and close the lid repetitively after it's cooled, it keeps rising.

I had a sample that i checked toward the end of the boil yesterday, that was initially (hot) low 9"s...Came back to it maybe 5 or so minutes (could have been 10) and opened the lid and reclosed it, and i got 13....Then over the next few minutes i proceeded to open, close, check, open, close, check, and the number eventually got to 15...No way my mash efficiency is that good! Not after a 4kg grain bill in a single batch.

It has me wondering, there must be an optimal time after drawing the sample and placing it on the lens when the refractometer is most accurate.

Has anyone else had this happen to them before? I'm not sure if it's normal, or if my refract is fucked. Calibrated it to zero too...

What's your process for using your refractometer in the boil? Explicit step by step instructions please...
 

geneabovill

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Dunno much about refractometer use, but would the water evaporate leaving a more concentrated sample?
 

bignath

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Dunno much about refractometer use, but would the water evaporate leaving a more concentrated sample?
If it was still hot it would.

This was ten or so minutes after three drops were placed on the lens. Would have been cold for sure. three droplets cool down almost instantly.
 

NewtownClown

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If it was still hot it would.

This was ten or so minutes after three drops were placed on the lens. Would have been cold for sure. three droplets cool down almost instantly.

The correct procedure is to take your reading immediately. If it is a non-ATC refractometer, as soon as the wort has cooled to 20c, which, as you point out, is pretty quic with just three drops.

I have noted with my ATC refractometer that no matter with cooled or boiling wort, it does creep higher if left for even just 5 minutes. Hot, dry days more so than cool or humid days. So I believe it is evaporation, perhaps more a drying out of the wort on the lens.
 

nala

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Hi brewers,

for all of the refractometer lovers...

Have been using my refractometer for the past few years as i much prefer it to the hydrometer. I don't actually own a hydro, i gave it to my mate so he could get into brewing.

When i take my readings during the boil, i place three drops on the lense, close the lid and look through it. Write down the number.

But yesterday i noticed something i hadn't spotted before. If i leave it, the number is higher than it was when i first took the reading.

Cooled sample....yeah i know, i know... BUT, if i open and close the lid repetitively after it's cooled, it keeps rising.

I had a sample that i checked toward the end of the boil yesterday, that was initially (hot) low 9"s...Came back to it maybe 5 or so minutes (could have been 10) and opened the lid and reclosed it, and i got 13....Then over the next few minutes i proceeded to open, close, check, open, close, check, and the number eventually got to 15...No way my mash efficiency is that good! Not after a 4kg grain bill in a single batch.

It has me wondering, there must be an optimal time after drawing the sample and placing it on the lens when the refractometer is most accurate.

Has anyone else had this happen to them before? I'm not sure if it's normal, or if my refract is fucked. Calibrated it to zero too...

What's your process for using your refractometer in the boil? Explicit step by step instructions please...
Nathan, I have not had this happen but I think your sample drawn with a pipette is too hot and when it cools leaves a residual skin on the lens. I no longer use a pipette for several reasons, one the possibility of contamination not so in the boil but for ongoing refractor measurements, I bought 500 cotton buds from Reject Shop ($2 for 500)2012_10_21_16.53.48.jpg and I use these exclusively to dip into wort and smear the refractomter lens, the sample is so small but ample for the reading and is at ambient in a split second.
 

Spiesy

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But isn't there the chance that some of the heavier and stickier particles in your sample might stick to the cotton tip?

Nathan, I have not had this happen but I think your sample drawn with a pipette is too hot and when it cools leaves a residual skin on the lens. I no longer use a pipette for several reasons, one the possibility of contamination not so in the boil but for ongoing refractor measurements, I bought 500 cotton buds from Reject Shop ($2 for 500)View attachment 58424 and I use these exclusively to dip into wort and smear the refractomter lens, the sample is so small but ample for the reading and is at ambient in a split second.
 

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