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using a refractometer

MRMARTINSALES

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Hi all,

I use a refractometer to measure the sugar content before i start fermentation and during fermentations. I find that the readings i get are inaccurate. one minute it reds 7 brix. then i take another reading and its 8. I wondered if anybody could tell me how to properly use a refractometer or suggest other alternatives to measuring sugar content to work out ABV. any suggestions would be greatly appreciated
 

philm63

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I use my refractometer only during the brewing process, then switch to the hydrometer for OG and FG readings.

As a rule;  use a hydrometer for my final OG reading after running the wort into the fermenter. Once the yeast has been pitched and mixed well, I draw a sample into a graduated cylinder intended for this use and drop in my hydrometer and note the initial reading.

Because I drew the sample post-pitch, it ferments at about the same rate as the wort in my fermenter (I keep them side by side in the fermentation fridge). This way; I can check the gravity any time I want without risking infection in the fermenter.

You may use a refractometer for checking gravity during fermentation but will likely get erroneous readings as, for reasons beyond my current experience, alcohol seems to affect the way light passes through the fermenting beer giving "fuzzy" readings which is why I rely primarily on my hydrometer for readings from OG to FG.

There is a small correction factor between the two instruments I use, I simply note this on my brew sheet and let it be what it is. The readings on the refractometer can be calibrated using distilled water so I tend to trust those readings, and make my corrections on the hydrometer.

In summary, I use the numbers on the refractometer to track the gravity during the brew, and I use the hydrometer to get the numbers I need for calculating my ABV.
 

mbg

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I still check with a hydrometer too - not enough confidence in the refractometer yet. I experimented a little and found technique is inportant. Make sure the device is clean (cleaned with water) and dried completely. Put 2-3 drops on the glass close to the hinged top piece. Slowly lay the top piece down and let the liquid flow to cover the entire surface. Make sure there are no air bubbles (if there are start over). I always take two readings. This is just a theory (I don't know that it's true) but even though the refractometer is ATC if you put too many hot samples on it in a short period of time I think the results can be skewed (because you are heating up the glass). I could be way off base here though. Plus ge some distilled water & calibrate frequently.

Mike
 

tom_hampton

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The blurry line is caused by the suspended yeast.  I draw my samples directly from the fermenter.  I estimate the visual center of the blurry area and use that as my reading.  If I'm unsure, I will let the sample settle for 20 minutes or so in the fridge.  My visual center hasn't been off by more than 0.2 brix, yet.

 

MaltLicker

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Walmart has a four-pack of stainless condiment cups ($1) that are perfect for taking wort samples.  It takes so little wort for the reading that the sample spreads across the stainless cup' bottom and cools amazingly fast.  Boiling wort can be cool to the touch in less than a minute with a little swirling.  In the summer, I put some cooled water/ice in a cereal bowl to speed the cooling if needed.  I find cooled wort gives a much sharper line on the Brix scales for easier reading.
 
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