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-   -   Hydrometer vs. Refractometer Reading (http://www.homebrewtalk.com/f163/hydrometer-vs-refractometer-reading-381405/)

oasisbliss 01-14-2013 04:17 PM

Hydrometer vs. Refractometer Reading
 
I just got done doing a bavarian hefe (thanks Ed Wort!)
here is what I got on my gravity readings...after chilling wort post boil.
I pulled a sample for my hydrometer and it was cooled to about 70f I got 1.052
then I took the same sample on my refractometer (that was calibrated with distilled water) that was 1.060
Can anyone explain this big difference?

Thanks for input

RmikeVT 01-14-2013 04:19 PM

have you calibrated your hydrometer in 60* distilled water? I know my hydrometer reads about 4 points too low.

Bobby_M 01-14-2013 04:30 PM

Right, most hydrometers are calibrated to 59F. The other thing to check is the scale of your refractometer. What brix number lines up with that 1.060?

oasisbliss 01-14-2013 04:48 PM

15 is the brix for 1.060

Intimnasc 01-14-2013 04:53 PM

I wanted to look at refractometers at my Local Brew Store and the guy told me it was a waste for extract brewing that the hydrometer would be way more accurate. Is this correct?

bmac 01-14-2013 05:48 PM

Quote:

Originally Posted by Intimnasc
I wanted to look at refractometers at my Local Brew Store and the guy told me it was a waste for extract brewing that the hydrometer would be way more accurate. Is this correct?

Refractometers are great at taking quick readings while all grain brewing. I use mine to check my run off gravity near the end of sparging, to take pre boil gravity, mid boil gravity just to make sure i'm where i thought i would be and post boil to get my starting gravity numbers. With an atc refractometer you don't need to cool the wort and you only need a couple of drops of wort to get an accurate reading. After fermentation is complete you will need to make adjustments to the reading you get from a refractometer due to alcohol being present, but there are calculators online or in beersmith that will make that a piece of cake.

johnp 01-14-2013 06:20 PM

Quote:

Originally Posted by Intimnasc
I wanted to look at refractometers at my Local Brew Store and the guy told me it was a waste for extract brewing that the hydrometer would be way more accurate. Is this correct?

It's not that they are more accurate. You don't need to check starting gravity with extract because you know exactly how much sugar you have in the beer.

Plus you can't use a refrac to determine FG, due to the presence of alcohol, though there are converters available online.

So I'd say he was correct that refractometers are less practical for extract, but not because they are any less accurate.

oasisbliss 01-14-2013 06:37 PM

I am doing AG - my biggest question is why the big difference? from 1.060 to 1.052 ?

librewer 01-14-2013 07:09 PM

Quote:

Originally Posted by RmikeVT (Post 4783870)
have you calibrated your hydrometer in 60* distilled water? I know my hydrometer reads about 4 points too low.

This... grab a jug of distilled water and check it. If you have an adjustment screw, adjust your refractometer. As far as the hydrometer, if it was calibrated at 59 (should see this stamped/printed somewhere on it) then your reading at 70 would be about 1 point off.... resulting in a corrected 1.053 SG.

Bobby_M 01-15-2013 06:28 PM

I can't figure out that wide of a discrepancy but librewer does show that the actual temp adjusted SG was probably 1.053.

The issue with the refractometer can be related to the calibration and actual handling. First, if you calibrated it inside the house at 68F room temp and then used it outside in 34F, you have a calibration issue. Try recalibrating when the instrument is temp conditioned to where you'll be measuring. The second issue that can result in an inflated gravity reading on a refractometer is evaporative concentration. If you take 1/2mL of sample wort and drop it on the prism where it flattens out to a paper thin layer, you can easily evaporate out 1/10th of the volume and therefore concentrate the sugar content. I always take my pipet with sample and invert it into a small cup of icewater just to knock the sample temp down closer to ambient temps to avoid this issue. Also, getting the cover down on the sample very quickly helps.


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