Refractometer accuracy

[Nmnbrewer]

So I took some readings recently from obviously finished fermentations and the readings on the refractometer were reading like 1023-1025. Started at 1055 btw. Tasted it. No residual sweetness that I could tell. Tried the hydrometer and that reads 1008. That seems more accurate. Question is, what could be affecting the refractometer readings so significantly? Should i be using a new pipette every time? Is there an adjustment? Etc etc.

 

[Nmnbrewer]

May have solved my own issue. Didn't realize that post fermentation readings aren't accurate with a refractometer.

 

[kh54s10]

Yes the hydrometer is more accurate. The refractometer reading is skewed with the presence of alcohol and you need to correct. There are some online calculators. Brewers Friend has one. Sean Terrill has written one that is widely quoted as one of the most accurate. I don't have a link.

 

[LarMoeCur]

Like Kb54S10 said you can use your refactometer post fermentation if you have the OG. There are a few calculators on the net that will make corrections for you.

On a side note. Make sure you calibrate your hydrometer too. The cheap ones can be off by quite a bit.

 

[balrog]

On a side note. Make sure you calibrate your hydrometer too. The cheap ones can be off by quite a bit.

Same is true for refractometer, FWIW; you should double check that as well.

 

[Morrey]

I did this:

Plain distilled water at 60F and took a reading with my floating hydrometer to verify it was reading 1.000 and it was. I then read the same DI water with my refractometer and it was slightly off zero so I set to read zero.

Made a small batch of wort (enough to float the hydrometer) by dissolving a few tablespoons of DME in some hot water making sure it was totally dissolved. Cooled to 60F and it read 1.055 with the floating hydrometer. Since I had confirmed it was at zero with DI water, I trusted this reading to be accurate. I read with refractometer and it was 1.057 so I adjusted the screw so it would read 1.055.

My experiences are that the floating hydrometer when checked as I did, is typically more accurate. The convenience of the refractometer is the allure, but with some calibrating, it is good to go. Post (or during) fermentation readings with your refractometer needs to use an online calculator but is really simple.

 

[brick_haus]

You should calibrate you refractometer with distilled water every time you use it. It is not uncommon for mine to be off as much as .005 points between cold (outside air temp) early pre boil readings and warmer afternoons when gauging starting grav.
In other words, the reading changes dramatically when the refractometer itself changes temperature. Calibrate multiple times during the brew day.

 

[LarMoeCur]

I did this:
Made a small batch of wort (enough to float the hydrometer) by dissolving a few tablespoons of DME in some hot water making sure it was totally dissolved. Cooled to 60F and it read 1.055 with the floating hydrometer. Since I had confirmed it was at zero with DI water, I trusted this reading to be accurate. I read with refractometer and it was 1.057 so I adjusted the screw so it would read 1.055.

Does your refactometer have both Brix and Gravity readings? If so only use the Brix side reading. Use a chart or program to covert Brix to Gravity. The duel indicated meters are skewed up on the gravity side. The one's I've seen are always .003-.004 off on the gravity reading but if I plug the Brix into BeerSmith it's right on with my hydrometer.

 

[Morrey]

Does your refactometer have both Brix and Gravity readings? If so only use the Brix side reading. Use a chart or program to covert Brix to Gravity. The duel indicated meters are skewed up on the gravity side. The one's I've seen are always .003-.004 off on the gravity reading but if I plug the Brix into BeerSmith it's right on with my hydrometer.

I started using the Brix scale (mine has both scales) so I could use an online program and get post fermentation SG readings with the refractometer. I also have a Milwaukee digital Brix refractometer so I wanted to make sure all of my devices had an accurate wort correction factor. After I confirmed the hydrometer was accurate, I then discovered both the digital and handheld refractometers were slightly off. I am able to get a correction factor added in for calculations albeit a very minimal issue.