Will suspended yeast affect Refractometer reading?

[mhermetz]

I recently started fermenting out of kegs. I took my first sample after running about a pint out of yeast sludge. When I took the sample it was not 100% clear, it definitely had yeast still in suspension. Anyway my reading came out to 3.8 brix, or 1.020. If that's true it means my fermentation completely crapped out. Just wondering if that cloudy sample affected my reading? I didn't have enough time to re-check with my trusty Hydrometer.

 

[Aristotelian]

You need to put your current Brix reading in a refractometer calculator along with your OG to account for alcohol in the beer. Use a refractometer calculator for during/after fermentation. I am getting different numbers for my current batch from these calculators so I am not sure about their accuracy. Regardless, if your Brix reading is stable, you can be pretty confident it has reached final gravity and it should be way below 1.020 depending on your OG.

http://www.northernbrewer.com/learn/resources/refractometer-calculator/

http://www.brewersfriend.com/refractometer-calculator/

 

[mhermetz]

humm yup that's telling me 1.006. cool

 

[microbusbrewery]

+1 what Aristotelian said. Once fermentation starts, the presence of alcohol changes the refractive index of the solution. The calculators help to adjust for this. Like you said, the yeast is in suspension, not solution, so it doesn't change the refractive index of the solution, but it can make it more difficult to get an accurate reading. For example, the blue border isn't as sharp/well-defined when there's lots of yeast in suspension. So if a perfectly clear sample reads 3.8, a sample with a bunch of yeast might show a cloudy border from 3.7 - 3.9.