Refractometer Problem?

[Duff]

This is the 3rd brew in a row I've done where my refractometer is giving me a pre-boil reading equivilent to 97% efficiency :blink:

I made a Dunkelweizen today OG:1.056. ProMash pre-boil is 1.044 (11.4 Brix). My refractometer read 14 Brix (1.054), my hydrometer reading was 1.045. This is after stirring the wort thoroughly for several minutes to ensure even distribution of sugars.

Now, simple answer is it's not calibrated correctly, I've checked several times and it is fine with boiled, cooled water. Further, when the boil has finished and the wort cooled (as with the other two) it gives me the correct anticipated OG. Has anyone had any issues like this with their refractometers? It's quite off putting when you are second guessing in your mind about the upcoming hop additions.

Cheers.

 

[mika]

Is it just that your refractomer does not have ATC (Automatic Temp Compensation) and you're seeing an inflated reading.
Did you cool the sample when you checked with the hydrometer ?

 

[Duff]

Is it just that your refractomer does not have ATC (Automatic Temp Compensation) and you're seeing an inflated reading.
Did you cool the sample when you checked with the hydrometer ?

It has the ATC and the hydrometer sample was cooled. This has only occured for the last 3 brews, before that no problem.

 

[mika]

If the reading was good once the wort had cooled it would have to point to a problem with the ATC or something temp related :unsure: I'm still waiting for my refractometer, have to verify my damn paypal account :angry: so can't offer anymore advice.

 

[pint of lager]

Have you calibrated the refractometer to zero with distilled water? The easiest way to obtain distilled water is to use a few drops of condensed steam from the kettle lid, or hold a spoon in the vapour path of the steam escaping. Also check that your hydrometer floats at 1.000 in water at 20 deg C.

You could also check both the hydrometer and refractometer with a known sugar sample. 100 gms of sugar dissolved in 1 litre of water is supposed to give an sg of 1.040. Have never measured this myself.

Is the glass landing and the flip down plastic cover spotless? If wort has at some time dried on the cover (both top and bottom sides) or the glass bed, this would give you an incorrect higher reading. Is the cover seating flat as it has always done in the past? If there is dried wort in the hinge, this may be causing it to not seat correctly.

 

[Gulf Brewery]

Is it just that your refractomer does not have ATC (Automatic Temp Compensation) and you're seeing an inflated reading.
Did you cool the sample when you checked with the hydrometer ?

It has the ATC and the hydrometer sample was cooled. This has only occured for the last 3 brews, before that no problem.

We have had erroneous readings in the brewery using a refractometer. I think the ATC refers to correction for the ambient temperature, not the wort sample. We find the safest and most accurate way is to cool the sample and then measure.

Cheers
Pedro

 

[Zwickel]

Gday mates,

the ATC does not correct the temp of the sample.
The ATC avoids only an offset of zero-calibration.
Thats only a mechanical balancing of the zero point.

Anyway that ATC works only within a certain range.
If you left the refractometer laying in the sunlight, youll not get a proper reading.
The ATC will run out of range.
Also if the temp of the sample is too high.

Thats a physical matter, a cold samples density is higher than that of a hot one.
A refractometer cantt correct the sample!

To get proper readings, the refractometer itself should be at 20C.

just my 2 cnt.

 

[Darren]

I have been dunking my refractometer into the boiling wort waiting 15 seconds and then reading. It is always the same as the hydrometer.
I would check your hydrometer as it the most likely to break and be reading incorrectly.

cheers

Darren

 

[Zwickel]

I have been dunkimg my refracto into the boiling wort waiting 15 seconds and then reading. It is always the same as the hydrometer.

Sorry Darren,

a hot wort, has never the same density as a cold one.
The refractometer has no device to adjust its optical lens to another refraction.
It only can compensate the drift of zero line.

just my 2 cent

 

[Darren]

I have been dunkimg my refracto into the boiling wort waiting 15 seconds and then reading. It is always the same as the hydrometer.

Sorry Darren,

a hot wort, has never the same density as a cold one.
The refractometer has no device to adjust its optical lens to another refraction.
It only can compensate the drift of zero line.

just my 2 cent

No need to be sorry Zwickel,

The wort reaches ambient almost immediately as it is essentially only about 100 microlitres in volume
If it is too hot the line is blurred, as it cools the line becomes sharper.

Done it dozens of times now. Try it yourself.


cheers

Darren

 

[mika]

Zwickel, Darren, would be interesting to take a measurement the way the other does it and then do it your way and let us know if there is any difference in the reading.

 

[Darren]

Zwickel, Darren, would be interesting to take a measurement the way the other does it and then do it your way and let us know if there is any difference in the reading.

Mika,

When I first got my refractometer I was sooo careful not to damage it and also use it as per instructions. As time went on I got lazier and lazier. In the end I just dunked it in and it worked.
I always take a flame-out (hot with refractometer) and post chill (with hydrometer) They always read within the limit of sensitivity of either device (never more than 4 SG points apart).

Just my observations.

cheers

Darren

I should have added. Most false results from a refractometer come from not washing the prism or lid.
If it is slightly wet from water or wort it will greatly skew your results.

 

[Zwickel]

Darren,

the compound of the device will cool down your sample very quickly, thats why your reading is close to the real value.
But... dont dip the refractometer into the hot wort or never leave it lying in the sunlight.

sure your readings will be far away from its original.

when the horizon is unsharp, the reason is mostly a cloudy wort.

You may take an experiment. Take clear water and add some powder.
Youll get a very unsharp horizon.

To resolve that problem, you may press the lid to the device, so the layer of wort becomes thinner and the horizon will sharpen.

Cheers

 

[Darren]

Hi Zwickel,

I have watched the line become sharper as the wort within the chamber cools. Try it yourself. Reads the same 20 seconds afterwards as it does 10 minutes later.

BTW, Cloudy wort will not effect SG or Refractive index.

cheers

Darren

I agree that leaving the whole unit in the sunlight will adversely heat it up and cause problems.

 

[Zwickel]

BTW, Cloudy wort will not effect SG or Refractive index.

thats absolutely right.
but the clarity of the sample is responsible for the sharpness.

lets have a beer :beer:

 

[Darren]

Zwickel,

:beer:

cheers

Darren

 

[sqyre]

Hi, i've just been skimming through the posts on refractometer problems and a few posts mention the word "DUNKING".
What ever you do dont submerge any part of your refractometer into any liquid as the seals in these things arn't the best. As soon as you get any moisture inside them they are stuffed.

I have been using refractometers for about 10 years (for testing coolant levels in machinery) and the biggest cause of damage is people submering the refractometers in the water.( even only the tip. )

The best way to take a reading ( in my experience) is to remove a small sample in a cup or whatever... and leave to reach room tempreture before testing. Apply 2-3 drops to the glass by dipping the end of a clean spoon or something into the cooled wort sample and use the drops off the end of the spoon.

To keep the reading acurate all the readings you take after the first reading should be close to the same tempreture as the first reading you took. (this also applies to calibration, but not sure how you guys do that as we calibrate to the water before the addition of soluble oils,etc.)

Hope this helps... :blink:

 

[Zwickel]

Hi sqyre,

thats absolutely my position :super:

 

[Darren]

Hi, i've just been skimming through the posts on refractometer problems and a few posts mention the word "DUNKING".
What ever you do dont submerge any part of your refractometer into any liquid as the seals in these things arn't the best. As soon as you get any moisture inside them they are stuffed.

I have been using refractometers for about 10 years (for testing coolant levels in machinery) and the biggest cause of damage is people submering the refractometers in the water.( even only the tip. )

The best way to take a reading ( in my experience) is to remove a small sample in a cup or whatever... and leave to reach room tempreture before testing. Apply 2-3 drops to the glass by dipping the end of a clean spoon or something into the cooled wort sample and use the drops off the end of the spoon.

To keep the reading acurate all the readings you take after the first reading should be close to the same tempreture as the first reading you took. (this also applies to calibration, but not sure how you guys do that as we calibrate to the water before the addition of soluble oils,etc.)

Hope this helps... :blink:

Sqyre,
Interesting post. I have had my brewing hydrometer for at least two years and have dunked it many times. It is just the tip, the same thing that you drop your oil on.
Btw, I have used lab refractometers to measure sucrose and salt solutions for 20 or more years. I would never be stupid enough to submerge the whole thing in the fluid.

Also, water on the lens will not be a problem with oil as the two don't mix. Water on the lens with wort will make a considerable difference.


cheers

Darren

 

[Zwickel]

Darren,
it also depends on the quality of the device.

Some of the very cheap one dont allow to get dunked into the wort. Not even the tip of it.

Maybe you are owner of a very good one, so you are lucky.

But other hand, better not to advice anyone to do the same, some of that equipment will die very quickly.

Just my 2 cnt.