Question on Refractometer Readings

Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum

Help Support Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum:

Joined
Mar 12, 2022
Messages
8
Reaction score
2
Hello.
I've been home brewing beer for about a year now. Typically once a week.
I'm not sure if I'm doing something wrong when using my refractometer.
I can't find anyone else describing this same issue so I'll try to explain thoroughly.

I brew small batches about 3 gallons to make a case of 12oz bottles.

When I'm done chilling I pour the beer through a strainer into my fermenting bucket and then take a small sample with a sanitized dropper.

I put a few drops on a clean and dry refractometer and close the cover.

Then I put the lid on the fermenter, shake it and add the yeast and airlock.

I go back to the refractometer and take a look at the gravity reading.
Set the refractometer down and clean up a little.
A few minutes later I'll lift the lid of the refractometer and drop it back down and take another reading and the gravity has gone up. If I set it down for a while more it keeps going up every time I do this.

For instance, today I brewed a barley wine that should of had an original gravity of 1.098.
When I checked it the first time it's 1.090. I wait 5 minutes and it's 1.093. 5 minutes more and it's 1.098. 5 more and it's 1.101.

I brewed a 10% stout recently and kept checking the OG reading (from the same sample) and eventually it was off the chart.
(The chart goes to 1.130)

Now I know I should probably use a hydrometer but honestly this reading isn't that critical to me, just nice to have.
And with these being such small batches I'd rather not waste a beer to take the reading. (I do use a hydrometer pre-boil and for the final gravity)

Any advice is welcome.

Thanks.
 

PCABrewing

Recreational Brewer
Joined
Oct 28, 2021
Messages
501
Reaction score
479
Hello.
I've been home brewing beer for about a year now. Typically once a week.
I'm not sure if I'm doing something wrong when using my refractometer.
I can't find anyone else describing this same issue so I'll try to explain thoroughly.

I brew small batches about 3 gallons to make a case of 12oz bottles.

When I'm done chilling I pour the beer through a strainer into my fermenting bucket and then take a small sample with a sanitized dropper.

I put a few drops on a clean and dry refractometer and close the cover.

Then I put the lid on the fermenter, shake it and add the yeast and airlock.

I go back to the refractometer and take a look at the gravity reading.
Set the refractometer down and clean up a little.
A few minutes later I'll lift the lid of the refractometer and drop it back down and take another reading and the gravity has gone up. If I set it down for a while more it keeps going up every time I do this.

For instance, today I brewed a barley wine that should of had an original gravity of 1.098.
When I checked it the first time it's 1.090. I wait 5 minutes and it's 1.093. 5 minutes more and it's 1.098. 5 more and it's 1.101.

I brewed a 10% stout recently and kept checking the OG reading (from the same sample) and eventually it was off the chart.
(The chart goes to 1.130)

Now I know I should probably use a hydrometer but honestly this reading isn't that critical to me, just nice to have.
And with these being such small batches I'd rather not waste a beer to take the reading. (I do use a hydrometer pre-boil and for the final gravity)

Any advice is welcome.

Thanks.
Evaporation, maybe enhanced by the act of opening and closing the lid on the refractometer?
Just a guess.. As the water evaporates the density will increase.
I usually take my reading then clean the tool. If I want another read I'll use a freshly drawn drop.
But I wouldn't think it would evaporate that fast with the lid down.
What temp are you starting at?
 
OP
OP
H
Joined
Mar 12, 2022
Messages
8
Reaction score
2
Thanks for the reply.
These readings are taken after cooling and just before adding the yeast so around room temperature.
Usually about 70 degrees Fahrenheit.

Assuming it's evaporation, then my first measurement would be the most accurate right?
Maybe I just need to start doing 3 samples and average them before adding the yeast.

Thanks again.
 

PCABrewing

Recreational Brewer
Joined
Oct 28, 2021
Messages
501
Reaction score
479
Thanks for the reply.
These readings are taken after cooling and just before adding the yeast so around room temperature.
Usually about 70 degrees Fahrenheit.

Assuming it's evaporation, then my first measurement would be the most accurate right?
Maybe I just need to start doing 3 samples and average them before adding the yeast.

Thanks again.
Have you tried calibrating it?
Then test with a generic sample to see if you get the same behavior.
Also, I usually back it up (cal.) with a Hydrometer to be sure the readings are close.
This would make a great Gauge R&R exercise :)
 
OP
OP
H
Joined
Mar 12, 2022
Messages
8
Reaction score
2
Yes when I started I zeroed it with distilled water and at that time I was also comparing it to my hydrometer readings.
Got into a groove (and lazy) so I've just been taking the readings from it as-is.
I think I noticed this issue when brewing strong beers.
It is a cheap hydrometer so maybe that has something to do with it.

I'm thinking of getting something like the Tilt so maybe that will help.

(I checked it with distilled water (67.3F) just now and it read 1.000 exactly)
 

tracer bullet

Supporting Member
HBT Supporter
Joined
Aug 10, 2020
Messages
1,487
Reaction score
1,283
Location
Minnesota
I agree it sounds kike evaporation. I have repeated readings but also just make new readings from the same sample. They tend to match my hydrometer almost perfectly if I've given things a few minutes for the sediment to settle first. (Meaning - I take a sample, half ounce or so, and let it sit for a bit. Then take the reading from it. Almost always see some sediment of some sort fall out. Not doing this did give me erratic readings).
 

Bobby_M

Vendor and Brewer
HBT Sponsor
Joined
Aug 3, 2006
Messages
26,416
Reaction score
6,348
Location
Whitehouse Station
It's definitely evaporation. There's probably a total of .02 ml liquid and it's spread out on about 2 square centimeters. That's a very high surface to volume ratio so even 5% evaporation is going to change your reading.
 
OP
OP
H
Joined
Mar 12, 2022
Messages
8
Reaction score
2
I like the idea of grabbing a half ounce sample and then finishing up the beer.
Thanks to everyone for the input.
 
Top