Hydrometer and Refractometer don't agree

[GarrettMD]

Refractometer reads 5.0 Brix
Hydrometer reads 1.008 SG

The temp of the beer is 70 degF

I have calibrated the refractometer with distilled water (didn't need to adjust anything, it was already right on 0 with the water).

This is a saison that's only been going for 4 days and is still bubbling slowly, so it's staying in the carboy regardless of which is correct, but I am concerned that the values don't match up. 5.0 Brix converts to 1.020, pretty far off from what the hydrometer is measuring.

What could be the issue? Is it more likely that the refractometer is wrong or the hydrometer? I'm guessing hydrometer since I haven't checked it against pure water, but what would cause it to be off that much?

 

[Squad1Guy]

Your refractometer won't be accurate with fermented wort. Stick with the hydrometer reading.

 

[Spartan1979]

If you do you a refractometer on fermenting wort you have to use a correction algorithm that approximates the actual gravity.

Here's one: http://www.brewersfriend.com/refractometer-calculator/

 

[taoisilent]

Refractometers are only accurate for unfermented wort or must. In the presence of alcohol (During or after fermentation), a calculator must be used to determine the correct Gravity reading.

Here's another one: Northernbrewer refractometer calculator/

Even though the calculated value is only an approximation, it's close enough for me, and It's so much easier to do with less wasted beer.

 

[betarhoalphadelta]

What was your OG?

Beersmith has a tool that will take your current Refrac reading and current hydro reading and give you the OG. Temp-correcting your current hydro reading to 1.009 and plugging it into Beersmith suggests that your OG was 1.038. Is that accurate?

It also has a tool that goes the opposite direction, so if I take an OG of 1.038 and a current refrac reading of 5.00 Brix, it spits 1.009 right back out at me.

Refractometers are just fine for final gravity, but you need to know the OG and apply certain calculations to get the current SG. You can't use the typical "multiply by 4" shortcut and get a meaningful SG due to the presence of alcohol.

 

[GarrettMD]

Thanks for the replies, I had never heard that refractometers couldn't be used during fermentation.

The OG was 1.045, which gives me a lower SG than 1.008 on those calcuators, but I'm just going to stick with the hydrometer for readings and check it against pure water to calibrate.

 

[GCPHomebrew]

Sean Terrill has a great calculator for this problem


Sent from my iPhone using Home Brew

 

[chemman14]

Refractometers are only accurate for unfermented wort or must. In the presence of alcohol (During or after fermentation), a calculator must be used to determine the correct Gravity reading.

Here's another one: Northernbrewer refractometer calculator/

Even though the calculated value is only an approximation, it's close enough for me, and It's so much easier to do with less wasted beer.

"wasted beer" You dont drink your hydrometer samples?

 

[Hello]

I've never been able to get my refractometer to read even remotely close to my hydrometer post fermentation. I understand there are calculators but it has always given me off results. I'll stick to a hydrometer; the right tool for the task, drinking my sample, and leave the refractometer for the wort. I always tell people it's possible to use a refractometer but results may not be accurate and frankly I advise against it based on experience. This thread further solidifies my opinion.