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For years, I've always taken my gravity readings with the hydrometer that came with my original homebrew kit. There's nothing wrong with it, but I've been thinking lately about switching over to a refractometer. While I enjoy tasting the progress of the beer at various stages, I'd like to limit the amount of beer I pull out of my batch to take gravity readings (an pbvious benefit of the refractometer).

Which of these two tools is more accurate/precise in taking gravity measurements?

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They are both very accurate when used correctly.

It's really best to use both

Refractometer is only accurate for OG readings. Benefit is a few drops for sample instead of 100-200ml. This is very useful when doing several samples trying to hit an OG in the mash/boil process.

You still need your hydrometer for fermentation gravity readings and FG.

Though there are some calculators to use refraction in FG they still need to be calibrated for each batch using a hydrometer.

Side note: Using a calculator, a refractometer and a hydrometer on FG can get you an unknown OG. Very useful when reverse engineering a commercial beer or when an OG reading was forgotten.

  • I agree that it is quite possible to use both but cannot understand why it is really best to use both. I like the fact that a refractomer is quick and simple to use for initial confirmation of OG (eg when mashing to test conversion). But IMHO unless the refractometer is SPECIFICALLY calibrated for beer wort or grape must (which many are not) then it can only serve as a close indicator of OG. Of course if one has a specifically calibrated wort refractomer then I concede that can be sensibly used for determining OG - with a hydrometer for FG. – barking.pete Jun 29 '18 at 10:11
  • @barking.pete use both. Refractometer for speed, accuracy and small sample size in OG readings. Hydrometer for FG because a refractometer isn't accurate when alcohol is in solution. – Evil Zymurgist Jun 29 '18 at 12:30
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I haven't used a hydrometer in years. I think they are worthless and you waste a fair amount of beer using one. You can do a very close estimate of your alcohol content by just using only a refractometer. I used a similar formula when making wine and remembered it for using it with beer too. I won't post the formula here (it's at this website). I never looked back and you should just throw away your hydrometer. Get a temperature compensating refractometer. They are a bit more expensive but you'll have it the rest of your life. Here is the calculator.

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Which of these two tools is more accurate/precise in taking gravity measurements?

Hydrometer. In my experiance.

It could be my cheap refractometer but i've noticed some inaccurate readings and I therefore don't trust it completely. I use the refractometer during the boil and fermentation just to get a general idea, but always a final reading with a hydrometer. I usually take the trub that is left in the kettle after the boil to get a accurate OG and the last bit of beer before the yeast cake after fermentation for a FG, to minimize the beer loss.

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    I agree. Refractometers are mainly used for determining initial sugar level in various brewing and food manufacturing processes. Refractometers work in relation to specific solution mixes. Once the solution mix is changed (eg brewed beer with alcohol present) the refractometer reading must be "suitably adjusted" to make it meaningful. Many refractomers are calibrated for sucrose (or glucose syrup) and give false readings with glucose/maltose mixes commonly found in wort.They are useful quick sample devices but a good hydrometer is usually more accurate( and precise) for general brewing needs. – barking.pete Jun 29 '18 at 10:02
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I recently switched too. One problem I noticed with the smaller sample is that if you pull from the top of the vessle you may get some oils or other less dense particles collected at the top. This layer of particles doesn't effect the hydrometer much reading since the sample size is much larger.

Precision - as long as temp is about 70f the hydrometer will be more reliable since it is based on a large sample and uses density.

Accuracy - the refractometer has to be recalibrated, using a hydrometer or by making a known solution with a scale. Also, a wort correction factor should be used.

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Yes, a refractometer is quick, requires only a drop rather than a larger sample, and is therefore easier to use with hot wort. But in my personal experience a hydrometer combined with a glass thermometer is the most reliable combination, always giving you an accurate reading no matter what. They measure the GRAVITY of the wort or beer at any time.

A refractometer, on the other hand, gives you the optical refraction of the wort or beer at whatever temperature the instrument has (a drop of wort or beer assumes the temperature of the instrument very quickly). How refraction relates to gravity depends on a number of factors including the sugar profile.

I know several seasoned pros who use a refractometer only to quickly check for deviations from the norm (i.e. to make sure the batch is doing more or less what it should) but if they need certainty and accuracy they break out the glassware.

For the same reason I also never use electronic thermometers. They may drift off calibration and you'll never know it. I've yet to see a glass (mercury) thermometer do that.

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