Refractometer Reading Increases over time

[Dicko72]

Hi Folks,

I use a refractometer for all pre-fermentation gravity readings and a hydrometer for post.

Yesterday I went through a calibration check of my refractometer.
I measured a preboil gravity of 1.047 on my refractometer (after conversion from Brix) which matched my hydrometer, all good!

I left the sample on the refractometer and went to it 15 minutes later and the gravity had gone up slightly.
After an hour the reading was now 1.060!

I have 2 refractometers and both had the same reading as it increased.

The readings were taken with the refractometer being close to 20C but not bang on, cooled wort sample too so I wouldn't expect any evaporation.

Is it normal for Brix readings to increase over time on a refractometer?


Thanks again.

D!CKO

 

[GalBrew]

It's a very small amount of liquid on a refrac, so I wouldn't be surprised if it evaporated quite quickly.

 

[meathead]

I work in diabetes care
When blood is left for a while the evaporation leads to a higher glucose reading
Same principle I guess

 

[spog]

I work in diabetes care
When blood is left for a while the evaporation leads to a higher glucose reading
Same principle I guess

am guessing that the h2o has evaporated leaving behind a more pure sample /higher reading for sugars. ...cheers..spog..

 

[Ducatiboy stu]

Mmmm.....most refractometers have a flip over cover that would stop evaporation...

 

[Mr. No-Tip]

Really interesting info! I always cover mine, but still good to know.

 

[Dicko72]

Interesting. I guess I'll make my readings as soon as the wort hits the glass and stabilizes. Thanks again everyone.

 

[Pagey]

Refractometers are temp sensitive are they not? Could there have been a change in temp?