Refractometer vs hydrometer

[enohcs]

I just got a refractometer and I'm testing it on a brew currently fermenting. My hydrometer is telling me the gravity is 1.046, but the refractometer is reading 12.4brix (which translates to 1.050). Which one do I trust? Does a hydrometer ever go out of calibration? I've checked it over and there it's not damaged in any way. When reading water, the refractometer is reading 0 and the hydrometer is reading 1.000

The other thing is at first reading my hydrometer read 1.049, but then settled at 1.046 after about 10min (I'm guessing due to bubbles that initially gathered, but then dispersed).

 

[Irrenarzt]

Always trust a hydrometer that reads 1.000 at 60F in distilled H2O. Refractometry is always going to yield questionable results for mixed solutions such as wort. Each chemical species (in this case, sugars) will refract light at different wavelengths and therefore you are only getting an average value. This might be fine for a quick check during fermentation but I always count on a good hydrometer for a more accurate reading.

 

[cfonnes]

After fermentation has started a refractometer is useless. I only use mine to tell me when to stop sparging.

 

[RoadKing]

Refractometers are best used when there is no alcohol present.
The alcohol skews the way the refractomer sees the sample.
If you know the starting gravity there are spread sheets that will be fairly accurate
with alcohol present. Beersmith has one built in, but here's one with a tutorial from morebeer. http://morebeer.com/learn_vids/vids_refract

 

[MalFet]

There's an effort going on to recalculate the post-fermentation refractometer correction formula, described here:

http://seanterrill.com/2011/04/07/refractometer-fg-results/

I've found the results on Sean's spreadsheet to be consistently very close, always between 1-2 points. Good enough for me.

 

[rico567]

After fermentation has started a refractometer is useless. I only use mine to tell me when to stop sparging.

I know there are correction factors that can enable a refractometer to be used post-fermentation, but my philosophy is to use each instrument where it's at its best. I use a refractometer through the mash & boil, down to checking the OG post-boil. I then use the hydrometer to check for FG post-ferment. It just doesn't seem all that difficult to use both.

 

[kcpup]

+1 on MalFet and Ricos posts. I want to move to all refractometer if possible. However, I haven't yet found a correction that suits me. I'm now going to try the link MalFet posted.

Like Rico, I use a refractometer pre-fermentation and I have a precision hydrometer for fermentation. It has a smaller scale and is good. However, it uses about 10-12 ounces per reading - hence my desire to be all refractometer.

I like accuracy most but would love it if I could only surrender about 2 ounces per batch! Thanks for the link MalFet.

OP, you need to do what you feel comfortable with.

I'd suggest doing side by side readings during fermentation (refractometer v hydrometer). This is the best way to develop confidence on gravity readings regardless of device. I'm continuing to do this in hopes I'll find the right compensation for my refractometer.

 

[iaefebs]

From what I see it might depend on whether your refractomter reads in Brix or SG or who the manufacturer is..I really and truly have no idea why people have trouble with a refractometer. I have taken many comparative samples and use an online convertor or BeerSmith 2.0 to convert fermenting beer from a refractometer to gravity. To me this question is one of those MYTHS that pop up continuously where the answer is... only to be used for pre boil or post boil... this is utter nonsense..I use it for every step of the process and have checked with a hydrometer and am very confident using the refractometer.... This being said you do have to do a correction to the reading, but with a calculator it is really simple,

 

[iaefebs]

after fermentation has started a refractometer is useless.

bs I use one all the time and have compared readings. Please cite an example for your post.

 

[nilo]

From what I see it might depend on whether your refractomter reads in Brix or SG or who the manufacturer is..I really and truly have no idea why people have trouble with a refractometer. I have taken many comparative samples and use an online convertor or BeerSmith 2.0 to convert fermenting beer from a refractometer to gravity. To me this question is one of those MYTHS that pop up continuously where the answer is... only to be used for pre boil or post boil... this is utter nonsense..I use it for every step of the process and have checked with a hydrometer and am very confident using the refractometer.... This being said you do have to do a correction to the reading, but with a calculator it is really simple,

+1, I also used a refractometer for OG and FG and during fermentation and had no issues to get accurate results.

 

[Mpavlik22]

i found this answer very spot on.

 

[jroot]

For my measurements I always use a properly calibrated refractometer. I see no problem using it for determining if a fermentation has completed. The reading will be the same if the fermentation has indeed finished because there is no more alcohol being produced or sugar to be consumed. Besides I don't really care if the ABV measurement is off by two or three tenths of a percent from its true value.

 

[iaefebs]

i found this answer very spot on.

Don't believe everything you read .. use real experience

 

[Mpavlik22]

Don't believe everything you read .. use real experience

????
Do you have any 'real experience' to prove otherwise? I've read this other places too....

 

[Brewskii]

The other thing is at first reading my hydrometer read 1.049, but then settled at 1.046 after about 10min (I'm guessing due to bubbles that initially gathered, but then dispersed).

Usually the readings go up, not down due to the temperature correction ( higher temps mean less viscous which gives low readings)

 

[Brewskii]

That applies to refractometers and hydrometers. Large commercial brewery's use temperature corrected spindles and compare all in their inventory to a control to place a further correction on them ( usually +- .02 SG or less) because there is variation from one to the next and they need to be certain they all are the same.
If using a spindle, however, to get accurate readings the sample cannot be carbonated. You must first de-gass the sample, usually by vigorously pouring it back and fourth a few times between two beer glasses.
I have a temp corrected spindle and use it infrequently. Refract is just as accurate and can be calibrated easily with adjustment scale. Try to keep temps as consistent as possible and use whichever you prefer. - my $0.02

 

[enohcs]

Usually the readings go up, not down due to the temperature correction ( higher temps mean less viscous which gives low readings)

There wasnt much of a temp change in this situation. Pulled sample at 55. Probably north of 60 by the time I get it in the test jar. Room temp was 70.
There were noticeable bubbles gathering around the hydrometer that went away within a few min.

 

[jetmac]

After fermentation has started a refractometer is useless. I only use mine to tell me when to stop sparging.

This is absolutley not true

 

[rack04]

????
Do you have any 'real experience' to prove otherwise? I've read this other places too....

I do and I have found the my fg corrected refractometer reading is spot on with the hydrometer reading. I have tested this on 4 occasions using the more beer calculator. The beersmith calculator is way off.

 

[Mpavlik22]

I do and I have found the my fg corrected refractometer reading is spot on with the hydrometer reading. I have tested this on 4 occasions using the more beer calculator. The beersmith calculator is way off.

Yes maybe in reading fg that may b the case because there is less sugars left in the wort, but I can personally say that my last 15 batches I have used both a hydrometer and a refractometer for my preboil and post boil readings and I have had as little as 1.002 and as high as 1.010 differences in readings.

 

[rack04]

Yes maybe in reading fg that may b the case because there is less sugars left in the wort, but I can personally say that my last 15 batches I have used both a hydrometer and a refractometer for my preboil and post boil readings and I have had as little as 1.002 and as high as 1.010 differences in readings.

What temp are you taking the pre and post boil readings? I assume both the hydrometer and refractometer and both calibrated.

 

[Mpavlik22]

What temp are you taking the pre and post boil readings? I assume both the hydrometer and refractometer and both calibrated.

Yes both calibrated in distiller water. Taken around 60F.

That is why I agree that the make-up of the wort (type of sugars it contains ie maltose, glucose, sucrose) affect the refractometer readings. Where a hydrometer takes a true density reading.

 

[MalFet]

Yes both calibrated in distiller water. Taken around 60F.

That is why I agree that the make-up of the wort (type of sugars it contains ie maltose, glucose, sucrose) affect the refractometer readings. Where a hydrometer takes a true density reading.

Actually, hydrometers are also calibrated for simple sucrose solutions, and likewise will be distorted by the presence of other sugars as well. If you want a true density reading, you need to involve yourself in some more sophisticated (=expensive) equipment.

Generally, though, hydrometers will be better correlates to actual density in most circumstances, though the question is whether or not the difference is large enough to matter to you. From my end (over literally hundreds of tests), I've never seen anything even close to a 10 point difference between a hydrometer and a refractometer with pre-fermentation wort. That's pretty weird. If I were in your shoes, I'd be inclined to check out my equipment. I've seen more variation in post-fermentation wort, but I've always found the readings to be close enough for my purposes — especially with Sean Terrill's new cubic regression.

 

[iaefebs]

????
Do you have any 'real experience' to prove otherwise? I've read this other places too....

Yes, at least to myself.