refractometer woes

[gadams00]

I just got a cheap refractometer with ATC as a gift and am having a hard time telling if it's messed up or not. I brewed a batch of APA last weekend and measured the OG with both the refractometer and a hydrometer. I calibrated the refractometer using distilled water. The refractometer read 13.6 brix and the hydrometer read 1.062 (actually 1.061, but the wort was at 168f, so that corrects to 1.062). I use beersmith, so I plugged the 13.6 brix into the refractometer tools and with the default brix correction factor of 1.02 I get a converted OG of 1.056, which is off. The problem is that when I plug in my values in the refractometer calibration dialog, I get a brix correction factor of 0.89944, and I believe that's never supposed to be less than 1.

After this I suspect that the refractometer is faulty, so I heat up a solution of 10g table sugar and 90g tap water and the refractometer reads 10 brix. I'm not sure what's wrong now.

I just bottled a batch that I brewed previously and tried the refractometer out for an FG measurement and got 5.7 brix (after calibrating to 0 with distilled water again) and 1.010 from the hydrometer. I know the OG for this batch from hydrometer reading was 1.056. In beersmith with the brix correction factor set to 0.89944, and using the fermenting wort gravity calculation type in the refractometer tools, if I enter 5.7 brix and OG as 1.056, it tells me the ABV is 7.06% and the corrected FG is 1.002. If I try the "original gravity of finished beer" calculation type and enter 5.7 brix and the FG of 1.010, it tells me the OG was 1.043 and the ABV is 4.36%. Neither of these is very close to the actual ABV, which is 6.0% based on the hydrometer readings for OG and FG.

Should I throw this refractometer in the garbage?

 

[Homercidal]

Hold on... You used 168F wort with your hydrometer?

All readings should be done at close to 60F. There is some room for correction, within reason, of course.

I've not used the beersmith FG correction before, but the one on my phone app seems to work just fine.

I'd sample some water with your hydrometer and check it's calibration. Make sure it's at 60F. Then add some amount of sugar (no heating) and measure it. Calibrate your refractometer and measure the sample and compare. It should be close, but sometimes you might have to adjust the correction factor for your particular refractometer.

And be sure to do all of this with the refractometer at room temp.

 

[Snafu]

Chances are you'll break it soon anyway,

 

[arch1tect]

I calibrated mine with the water I use to brew.

1) Drew a sample for my hydrometer and took a reading.
2) used same sample for refractometer.
3) entered into beersmith for calibration.


If you're going to use it for the FG you need the OG to account for the alcohol. It will always be off due to that.

 

[Diver165]

There is something not right with your math or conversion program.

Using the table provided by John Palmer if your sample was a 120F and you got a 1.061 reading a temp correction (0.0106) would be 1.0726. I don't even know what the hydrometer conversion numbers would be for a 168F wort sample.

 

[gadams00]

Sorry, i mistyped in the original post. The 1.061 reading at 168f was actually at 68f.

I have tried to calibrate my hydrometer and refractometer using sugar water at specific percentages (15g sugar to 135g water = 10% w/w, 30g sugar to 120g water = 20% w/w) and both give accurate readings for sugar solutions. I do have to heat the samples to around 130f to get the sugar to dissolve completely, but i'm applying temperature corrections to the hydrometer and the refractometer is supposed to automatically correct for temp unless I'm misinformed. Regardless, the readings are accurate for 10% and 20% sugar solutions, but the readings are off in the wrong/unexpected direction when using wort with the refractometer as compared to hydrometer readings, i.e. the refractometer reading equates to a lower gravity, when it's expected to be higher.

 

[Diver165]

I would say your refractometer you got off ebay is just what you said, cheap. Do you have access to another hydrometer to cross check?