Hydrometer vs Refractometer for OG

timtoos · Oct 14, 2017

Hi,

I have both a hydrometer and digital milwaukee refractometer (MA871) and find these units both tie up pretty good for OG.

Yesterday, I did a brew and my hydrometer, which I hate using and always reads +1 point high across the range) read a OG of 1050 so 1049 and my refractometer read 13B or 1053.

Which instrument would you guys trust more?

PS, the sample was at 21C on the hydrometer and given well chance to hit room temperature on the refractometer.

TIA

simon12 · Oct 14, 2017

I would trust the hydrometer, having had several hydrometers than always agreed and a refractometer that needed continuous recalibration to give correct readings.

chesters-mild · Oct 14, 2017

I always go with the refractometer for OG, and use a 'finishing hydrometer' for the FG
Cheers

GerritT · Oct 14, 2017

I have a hydrometer that I trust. And ordered a refractometer because I don't want to lose too much beer because of testing.

timtoos · Oct 15, 2017

Thanks for the advice guys. Usually both instruments read the same for OG. This brewday though they differ by 4 points. Not the end of the world I suppose but would love to know why.
Could it be different glucose sugars which are changing the refractometer value? If this is the case then the hydrometer is likely to be the more reliable value. I so want the refractometer to be correct.

mgkpancake · Oct 16, 2017

timtoos said:
Hi,

I have both a hydrometer and digital milwaukee refractometer (MA871) and find these units both tie up pretty good for OG.

Yesterday, I did a brew and my hydrometer, which I hate using and always reads +1 point high across the range) read a OG of 1050 so 1049 and my refractometer read 13B or 1053.

Which instrument would you guys trust more?

PS, the sample was at 21C on the hydrometer and given well chance to hit room temperature on the refractometer.

TIA

Use the refractometer on unfinished wort and after fermentation is done use your hydrometer. The alcohol will screw up your readings on on the refractometer but less so on the hydrometer. Over 1.075 gravity there is compensation calculations that need to be done to correct for the alcohol.

AdeDunn · Oct 22, 2017

I purchased a refractometer myself. The problem is, many of them are cheap and can be less than accurate. The second problem is if you use the same hydrometer for both OG and FG any inaccuracy won't matter, the ABV calculation will still be correct as both results will have the same margin of error. If however you use a refractometer for your OG, then a hydrometer for your FG, the margin of error for each can and probably will vary, meaning your ABV will be even more prone to error.

Mine has pretty much been relegated to the draw, or guide testing, as the first AG I did recently the refractometer reading had quite a large variation from the hydrometer reading. Meaning that for ABV calculation it's pretty much useless to me. :doh:

It's a cheapo one though, I'd say if you are going to get one you need to spend more or expect to end up leaving it in the draw.

Hydrometer vs Refractometer for OG

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