Hydrometer vs refractometer

[The8thfold]

Needing to replace my old hydrometer due to some butterfingers.... what are your guys option on refractometers vs hydrometers? Does one work more accurately, or should I just get both? Thanks!

 

[Cyclman]

I always have a hydrometer for ultimate accuracy. But refractometers are super convenient, especially with wort. If you want a very good estimate of beer gravity use this Calculator http://seanterrill.com/2012/01/06/refractometer-calculator/

 

[The8thfold]

I always have a hydrometer for ultimate accuracy. But refractometers are super convenient, especially with wort. If you want a very good estimate of beer gravity use this Calculator http://seanterrill.com/2012/01/06/refractometer-calculator/

Thanks!

 

[BroStefan]

Refractometers have their uses but also limits. What matters is the density of the sugar dissolved in the liquid. A hydrometer measures that directly. A refractometer measures a derivative characteristic that is only associated with the thing that matters.

I use my refractometer to monitor the mash but my hydrometer makes the official measurements of SG and OG

 

[ba-brewer]

buy one refractometer and two hydrometers.

 

[LarMoeCur]

I brew with both. But I'm obsessed with the numbers.

 

[gfarantes]

Seanterrill calculator never failed with me. I dont see a point in having a hydrometer anymore. Refractometer is more convenient, uses less wort/beer and less fragile.

 

[dyqik]

Warning: overly detailed nitpick ahead...

Refractometers have their uses but also limits. What matters is the density of the sugar dissolved in the liquid. A hydrometer measures that directly. A refractometer measures a derivative characteristic that is only associated with the thing that matters.

Not really, what really matters is the amount of (fermentable) sugar and alcohol dissolved in the liquid. A hydrometer infers this via density, while a refractometer infers it via refractive index. Both have potential issues - both are confounded by alcohol in solution or by non-fermentables - which is why my cider is currently at an SG of 0.997 and might have a little further to go.

However, in normal beer brewing, it's easier to cope with the confounding due to alcohol on a hydrometer, as alcohol reduces the density while sugar raises it, which means you can use apparent reduction in density as a measure of the progress of fermentation (although apparent attenuation overstates the amount of sugars in wort turned to alcohol), which is what's being done with the traditional use of OG and FG, and why people convert refractometer readings to gravities. For a refractometer, both alcohol and sugar increase the refractive index, and so you have to separate the effects of alcohol and sugar using a slightly more complex calculation, and the equivalent of apparent attenuation measured with a refractometer is less intuitively related to how far the fermentation has progressed.

If you wanted to, you could track progress by potential and actual ABV, which would give you real extract and real attenuation, using either a refractometer or a hydrometer. But most brewers and brewing information don't bother as gravities give enough information. For "normal" beers, it doesn't matter so much. If you are trying to compare something very dry, like a dry cider with something full-bodied, like a milk stout, then the gravities come with a lot of caveats.

 

[dyqik]

Seanterrill calculator never failed with me. I dont see a point in having a hydrometer anymore. Refractometer is more convenient, uses less wort/beer and less fragile.

There's been some further research on converting refractometer readings to real extracts and gravities that disagreed with the Seanterrill calculator, particular under partial fermentation. This was in the July/August 2017 Zymurgy (a couple of issues ago) in the article "Revisiting The Refractometer" on p48.

 

[WesternBrew]

Warning: overly detailed nitpick ahead...


However, in normal beer brewing, it's easier to cope with the confounding due to alcohol on a hydrometer, as alcohol reduces the density while sugar raises it, which means you can use apparent reduction in density as a measure of the progress of fermentation (although apparent attenuation overstates the amount of sugars in wort turned to alcohol), which is what's being done with the traditional use of OG and FG, and why people convert refractometer readings to gravities. For a refractometer, both alcohol and sugar increase the refractive index, and so you have to separate the effects of alcohol and sugar using a slightly more complex calculation, and the equivalent of apparent attenuation measured with a refractometer is less intuitively related to how far the fermentation has progressed.

+1 to this. I just learned my lesson with using my refractometer for FG. I thought I had a stalled fermentation because the refractometer was reading 1.033 for 3 days straight. Spent some time panicking and raising the temp to 75 before asking the guys at my LHBS. I took a sample for my hydrometer and it read 1.013.

I'm just amazed at how different the measurements can be.

 

[gfarantes]

There's been some further research on converting refractometer readings to real extracts and gravities that disagreed with the Seanterrill calculator, particular under partial fermentation. This was in the July/August 2017 Zymurgy (a couple of issues ago) in the article "Revisiting The Refractometer" on p48.

I’ll take a look. Thanks for the article!

 

[Silver_Is_Money]

I took the plunge and I intend to use exclusively my refractometer going forward. I'll be using Sean Terrill's calculator for FG's.

I did a test with a 10 Brix sugar solution I whipped up, and it read about 9.95 Brix. Given the likelihood that there are contaminants in the sugar, or more likely some moisture, I considered that to be a pretty good test.

 

[Pintabone]

I love using the refractometer over the hydrometer. I don't claim to understand the differences but if you can use a calculator to get to +- .002 when measuring your FG are you really that concerned? It's great just pulling a little of beer from the fermenter in a small glass to check the gravity. Especially if the fermenter has a spigot.

 

[Morrey]

Both....I use both every brew.

Test both floating hydrometer and refractometer with distilled water to make sure you get a baseline zero. I have 4 floating hydrometers and ONLY 1 of them read a true zero with Distilled water at 60F. The refractometer can be adjusted to zero with a set screw.

Then I tested apple juice with both and compared the readings. My refractometer was slightly off compared to the floating hydrometer, but since I trusted the reading of the hydrometer, I adjusted the refractometer to this same number. Once I set it, I haven't had issues with the two differing.

 

[Morrey]

+1 to this. I just learned my lesson with using my refractometer for FG. I thought I had a stalled fermentation because the refractometer was reading 1.033 for 3 days straight. Spent some time panicking and raising the temp to 75 before asking the guys at my LHBS. I took a sample for my hydrometer and it read 1.013.

I'm just amazed at how different the measurements can be.

That's the classic number....1.030....that a refractometer will read in the presence of alcohol when the real FG will be around 1.010. Next time you see a novice brewer (or old timer for that matter) post that their fermentation went wild but stalled out and stuck at 1.030, you can almost figure they used a refractometer and failed to convert the number due to alcohol being present.