Used my refractometer to brew beer, got wildly wrong results

[BillyZ]

I use an ATC refractometer to check the sg of my saltwater tank. Has been very accurate and a great tool for me. I was brewing beer with my brother a couple weekends back and I brought along my refractometer for testing the sg of the mash. (the pre-beer after first boiling the grains) The refractometer read WAY high. it read about 1.08+ when we were expecting 1.04 to 1.05. We used our old standby glass tube float hydrometer and read the 1.04 we were expecting.

At this point we're basically measuring the amount of sugar in the water.

Can anyone offer an explanation of why the refractometer read inncorrectly? I tested it with freshwater right then and it checked out ok.


just curious if anyone could offer any thoughts.

Thanks!

 

[TankGirl]

Temperature? Solids in the brew mixture?

 

[BillyZ]

hmm... i didn't think about other solids. there could verry well be bits in there. but wouldn't those skew the float readings as well? hmmm gotta do more research...

 

[Menagerie]

Trevor offers this: sugar is heavier than salt and the "standard curve" is different. Although you can use the same type of instrument, the calibrations are different for different molecules that you are testing.

 

[quarryshark]

Sure you were not just having double vision from too much sampling?

 

[revhtree]

I vote for quarryshark's reasoning....

 

[BillyZ]

Trevor offers this: sugar is heavier than salt and the "standard curve" is different. Although you can use the same type of instrument, the calibrations are different for different molecules that you are testing.

ahhhh... makes a lot of sense. so, i'll have to dig around alittle and see what that difference is. Probably the best way in the future will be to make sugar water solution of a known gravity and use that to calibrate.

Thank you trevor!

and thanks everyone else. Although there was plenty of sampling, the real sampling won't take place until next weekend... if I can hold out that long!

 

[Menagerie]

I guess it is helpful when Trevor reads over my shoulder