New refractometer doesn't match hyrdometer?!

Hi,

I just got a refractometer, and used it for the first time today.

It gave a reading of 11 plato on something my 60F hydrometer gave at 1.062.

I'm not sure what's up, especially because they both are accurately calibrated to give distilled water a 'zero' reading!

Any thoughts?

Did you check the instructions that came with the refractometer and the hydrometer? They need to be corrected/adjusted at different temps

Thanks, I definitely considered that though.

My hydrometer is configured for 60F, which I've accounted for. And my refractometer is supposedly ATC, meaning that it automatic calibrates to the atmospheric temperature.

Either way, the temp samples and ambient temp were roughly 70F. But I had a 1.015 difference in the readings.

EDIT: I explained ATC wrong above, and I'm aware that ATC refractometers need to be calibrated at a given temp, and I did that.

And my refractometer is supposedly ATC, meaning that it automatic calibrates to the atmospheric temperature.

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You still need to calibrate it. I have an ATC refractometer but it still says to calibrate it.

weirdboy said:

You still need to calibrate it. I have an ATC refractometer but it still says to calibrate it.

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Your're right. I minced words, it will work in any temp, but does need to be calibrated. And I did calibrate it. With distilled water, and it read 0.

But it still read the wort wrong compared to the hydrometer.

did you calibrate the hydrometer with distilled water?

I've thought of two things:

Dumb Thing - you are talking about unfermented wort, correct? Alcohol messes with the refractometer reading. (which you probably already know, like I said, dumb thing)

Not so dumb thing - Are you getting a large, bubble-free film of liquid when you close the cover? I've found that a lot of bubbles under the cover can affect the reading.

Oh wait, Three things! - was the wort mixed well for both samples? I've heard of faulty hydro readings due to stratification in wort.

Isn't there a correction factor, which is specific to each wort, needing to be used when measuring unfermented wort? I know each wort i produce, the correction factor is slightly different each time, and i can see this difference producing the problem the OP has stated above. I use beersmith, which has a "calibrate hydrometer" setting to generate this correction factor.

Just a thought.

cactusgarrett said:

Isn't there a correction factor, which is specific to each wort, needing to be used when measuring unfermented wort? I know each wort i produce, the correction factor is slightly different each time, and i can see this difference producing the problem the OP has stated above. I use beersmith, which has a "calibrate hydrometer" setting to generate this correction factor.

Just a thought.

Click to expand...

I think the correction factor you are talking about is to adjust for slight errors in how a hydrometer reads. For instance, one that reads 1.001 in distilled water at calibration temp needs to be corrected .001 (should read 1.000)

The refractometer calibration in Beersmith is a way to get your hydrometer reading and refractometer reading to agree. After it's set, the two instruments will agree for unfermented wort. As I said, fermenting wort has to have another correction applied (which Beersmith will also do), but that is separate from the 'calibration'.

wehumble said:

I think the correction factor you are talking about is to adjust for slight errors in how a hydrometer reads. For instance, one that reads 1.001 in distilled water at calibration temp needs to be corrected .001 (should read 1.000)

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complete calibration requires a second reading at higher density that you make with pickling salt and create a correction curve.
cheap hydrometers, usually most of the full range triple scale ones, are not very accurate. you're better off with a set of 3 narrow range hydrometers. they are more expensive, about $15 to $25 each, but made to higher standards, and are a LOT easier to read because the marks are farther apart.

if you are measuring wort after fermentation has begun, use this calculator
Onebeer.net :: Homebrew :: Refractometer Calculator

make sure that you calubrate your refractometer to 0-brix with distilled water

an ATC refractometer needs several seconds to ajust for temp, and it only has about a 20-30degree swing at most.

Arkador said:

if you are measuring wort after fermentation has begun, use this calculator
Onebeer.net :: Homebrew :: Refractometer Calculator

make sure that you calubrate your refractometer to 0-brix with distilled water

an ATC refractometer needs several seconds to ajust for temp, and it only has about a 20-30degree swing at most.

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I would bet that one would get the same reading on our cheap refractometers with either distilled or ordinary tap water. At least I can't tell the difference. I no longer bother with the distilled water and use tap water to check mine now and then. I've never had to adjust it.

Why would an ATC refractometer need several seconds to adjust for temp and the temp of what?

Isn't there a correction factor, which is specific to each wort, needing to be used when measuring unfermented wort?

Click to expand...

Correct

Brix refractometer readings are based on percentage sucrose in the solution.
Wort is not pure sucrose, contains many substances.
A correction factor is required to convert from a Brix reading of wort to the actual gravity of the wort.

As per ProMash.
The literature suggests this factor is between 1.02 and 1.06, with 1.04 often used as a default value.

Cheers,
ClaudiusB

Why would an ATC refractometer need several seconds to adjust for temp and the temp of what?

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Catt22 I think a lot of us are confused how a ATC refratometer works.
The only time they are correct if the refratometer was kept at a temp way outside its operating range.

Catt22 discussed the same problem a few weeks ago, can't find the post.


Cheers,
Claudius

Orangevango said:

did you calibrate the hydrometer with distilled water?

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yes for both hydrometer and refractometer. i mentioned that in the OP.

wehumble said:

I've thought of two things:

Dumb Thing - you are talking about unfermented wort, correct? Alcohol messes with the refractometer reading. (which you probably already know, like I said, dumb thing)

Not so dumb thing - Are you getting a large, bubble-free film of liquid when you close the cover? I've found that a lot of bubbles under the cover can affect the reading.

Oh wait, Three things! - was the wort mixed well for both samples? I've heard of faulty hydro readings due to stratification in wort.

Click to expand...

1. Yes, it is unfermented.
2. Yes, I made sure of that. And measure it at least 5 times.
3. Yes, I stirred it pre boil when I measured. And I also measured it post-boil, when it would have been well 'homogenized'. Both times the refractometer was very low compared to the hydrometer. The wierd thing is that the refractometer gave a preboil plato of about 9.75, and a post reading of about 11.00 - which is about the right change during my boil. However, it's much lower than it should be (my process is pretty consistent) and than my hydrometer says. Hyrdometer gave a post boil reading of 1.062.

wehumble said:

The refractometer calibration in Beersmith is a way to get your hydrometer reading and refractometer reading to agree. After it's set, the two instruments will agree for unfermented wort. As I said, fermenting wort has to have another correction applied (which Beersmith will also do), but that is separate from the 'calibration'.

Click to expand...

Right. This is what I'm talking about. It isn't a true "calibration" per se, just a correction done by Beersmith from hydro to refracto. It's just called "calibration" in Beersmith. My point, though, was that from wort to wort, this factor is different, and THAT might be a consideration for an off reading.

I had a d'oh moment when the refractometer reading was way low.
It turns out there was enough distilled water in my eyedropper to throw off the reading.
Now I fill and dump the eyedropper several times to make sure it's all wort.

Also, my hydrometer and refractometer are always within 0.001.
But I have to check to see whether one is always higher than the other.

HairyDogBrewing said:

I had a d'oh moment when the refractometer reading was way low.
It turns out there was enough distilled water in my eyedropper to throw off the reading.
Now I fill and dump the eyedropper several times to make sure it's all wort.

Also, my hydrometer and refractometer are always within 0.001.
But I have to check to see whether one is always higher than the other.

Click to expand...

Good thought for sure, I did this though, several times. Still wonky reading, and consistently wonky too!

Take readings from both - refracto & hydro to get your correction factor. Like ClaudiusB said, a correction of 1.02 to 1.06 should typcially be employed to bridge the difference between the two measurements for each batch of wort.

when I did mine, I used the wort from a starter that I knew from experience would be 1.040, and it's matched the hydro ever since.

LooyvilleLarry said:

when I did mine, I used the wort from a starter that I knew from experience would be 1.040, and it's matched the hydro ever since.

Click to expand...

Ok, I'm going to look into this further.

This might be my answer because all the readings from my refractometer were consistent, the pre and post boil readings even made sense (i could predict what it would be even though it was wrong), and the calibration is right. It is off by about 1.015 from my hydrometer though.

Ill fiddle with this and let you know.

1.015/1.000 = 1.02 correction factor

Really sounds like this is your issue.

I've accounted for this in BeerSmith now. I will play around with it over my next few batches to see how it works. Thanks!

That should work. I've also found the MoreBeer spreadsheet to me very accurate for fermenting wort.