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Old 04-08-2009, 05:55 PM   #1
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Default Do you trust your refractometer?

Hydrometer or Refractometer?

My "fermenting beer" corrected refract reading is 1.012 while my hydrometer reading is 1.019 on my Ordinary Bitter (only 3 days into fermentation).

For the Stout, the hydro says 1.024 but the refractometer (adjusted to "fermenting beer") says 1.017...

This is my first experience with the refractomer. It is supposed to be ATC but I've read distilled water at 2 different temps and have had to adjust the screw both times.

Please help me understand this thing!


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Old 04-08-2009, 05:59 PM   #2
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You need to make sure that you have:

1) Corrected your hydrometer in distilled water
2) The samples for the refractometer must be degree and bubble free
3) You must also make sure you have calibrated your refractometer using distilled water


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Old 04-08-2009, 06:05 PM   #3
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Here is my process:

Purchased distilled water.
Put some in a hydrometer tube and got it to 68
Put some on the lens and adjusted the screw down to 0% Brix.

On brew day:
took SG at 1.032.
took refractomer reading at 8% Brix
Entered those values into Beer Smith to store.

You said "degree and bubble free." I just want to make sure you meant "debris" free. Not pointing out any spelling BS. Just want to ensure I have your meaning.

Thanks
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Old 04-08-2009, 06:08 PM   #4
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Opps... yes "debris"

Also - did you use the "calibrate refractometer settings" in beersmith?
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Old 04-08-2009, 06:15 PM   #5
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The ATC feature adjusts the instrument for ambient temperatures. IOW, the temperature of the instrument, not the temperature of the sample.

It's possible that your SG reading was incorrect for some reason. Maybe the wort had stratified or was not mixed well.
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Old 04-08-2009, 06:23 PM   #6
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Good call on the ATC. Didn't know that.

After I got a JACKED up reading on my first AG for SG, I've been very cautious to stir the hell out of it before taking a reading but I guess there is always a chance that it wasn't enough...although I hit the target SG. Then I chill the sample to get better accuracy from the hydro. What do you mean by "stratified"?

JVD: Yes. I put the 1.032 in Beer Smith along with my 8% Brix reading. Gives me a conversion factor ( I think that's what they're calling it) of 0.99. Should those be done at 68 too?
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Old 04-08-2009, 06:57 PM   #7
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Stratified simply means that the wort will sometimes tend to form layers in the kettle of differing gravities. This can be a result of not mixing well after the runoff is collected or possibly due to temperature differences as the sparge progresses. I'm sure you've discovered that the initial runoff will be very of high gravity and this wort will tend to just lay in the bottom of the kettle. Subsequent lighter runoff can lay on top of this heavy wort and not mix well on its own. It sometimes takes more mixing than one would think. I've had this problem more than a few times. One indication is if you take multiple refractometer readings one after the other and they do not closely agree, then there's a good chance that it's not mixed well. It's likely not a problem with the refractometer as they are rather simple instruments and there's not a lot that can go wrong provided they are not dropped or otherwise abused. Even then, recalibration will usually fix the problem. I have never had to calibrate mine. Been using it as it came out of the box several years ago without problems. The sample need not be completely free of particulates (debris). What little difference they would make would likely not even be measurable by our methods. You can spin a hydrometer to shake off any bubbles and get a more accurate reading.

I just plugged the 8 brix refractometer and 1.019 hydrometer readings into the Promash utility for and it says your OG should have been 1.052. Something's not right, but I don't know what.

According to ProMash, for un-fermented wort, 8 Brix corresponds to 1.0305. This is only slighty off of your 1.032 reading and that could be due to the way you are reading the hydrometer or the calibration of the hydrometer itself. Some hydrometers are difficult to read due to the small gradation marks.
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Old 04-08-2009, 07:10 PM   #8
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I've heard mixed reviews about trusting the adjustments you make for readings after fermentation has begun. Some say that they're accurate, others... are less convinced.
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Old 04-08-2009, 07:15 PM   #9
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I generally don't use mine after fermentation has begun. Its not so much that I don't trust the conversion, but I like to have a taste of how things are going anyways. So why not use the hydrometer.
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Old 04-08-2009, 07:24 PM   #10
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Quote:
Originally Posted by the_bird View Post
I've heard mixed reviews about trusting the adjustments you make for readings after fermentation has begun. Some say that they're accurate, others... are less convinced.

Yes, I've read the same thing. I think the best that can be said is that it would be a reasonable approximation. There's also got to be some inherent
error in our reading of both the refractometer scales and the hydrometer gradations. I don't worry much about the gravity during fermentation. I use the refractometer mostly on brew day to get my OG during the boil so that I can make adjustments quickly if need be. After that, I'm only really interested in the FG to check the attenuation.


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