Refractometer Query

[Stuster]

I've given up on my refractometer - not happy with the reproducibility. I use the hydro - it works the same every time plus you can drink the sample.

I've found that refractometers can be really variable in their readings. I've been taking reading straight after each other that are different. I was showing OldBugMan at the last ISB brewday, readings from the kettle during the boil (should be stirred up enough that all readings are the same I thought) were different by up to 1P. :blink:

Maybe there's a reason those Chinese refractometers are cheap. :lol:

 

[Tony]

not happy with the reproducibility.

WOW :blink:

Biggest word of the day goes to............. GH

I love my refract. I like being able to take a simple sample of just a few drops as the mash progresses to check its gravity. When it stops increasing, i run it out and sparge.

Its spot on with the hydro too.

The thing i found produced reproducibility (hehe) problems for me was not stiring a mixtrue properly like when you are bringing the 1st runnings and sparge up to the boil in the kettle. If its not mixed in properly you will get a flase reading as you only take a 3 drop sample, not 100mls or so like in the hydro tube.

cheers

 

[PostModern]

If its not mixed in properly you will get a flase reading as you only take a 3 drop sample, not 100mls or so like in the hydro tube.

Reproducibility is inefficacious with amorphos stratification.

 

[Stuster]

Reproducibility is inefficacious with amorphous stratification.

Fixed that for ya.

 

[goatherder]

Reproducibility is inefficacious with amorphos stratification.

I'm laughing so hard right now...

 

[warrenlw63]

My own take on the whole thing is a refractometer is only of any real use for making small starter worts or if you fly sparge because you've got to get a quick reading to hit your sparge cutoff point.

Now I batch sparge I find mine bordering on redundant. Only time I use it is to take the specific gravity of no-chill wort. Even then I become very dubious. Putting a drop of liquid on the lens when close to boiling would have to give a highish reading when the sample cools to 20 degrees (assuming you're not using a temp correcting refractometer) because of the wisp of steam given off on such a tiny sample would surely increase the actual gravity ?? :unsure:

Warren -

 

[browndog]

We are struggling to get our second going ...... do I have amorphos stratification h34r:


cheers

Browndog

 

[Keith the Beer Guy]

Just a word about some of the criticisms offered about using refractometers.

I'm using one of mashmasters refractometers (the link is in the advertising bar above).

There's no doubt in my mind that I'm using it because I love toys, not because it helps me brew better beer.

That said, I love using it, I find it quick and simple to use. It gives reliable and consistent results.

You gotta remember its a piece of groovy scientific equipment and you need to both use it properly and look after it. Calibrate it before use, make sure the prism is entirely covered by your sample, dont have floaties in your sample, rinse it with clean water after use, dry the glass prism before storing it, blah, blah, blah.

Warren, one of the advantages of using a refractometer is that the temperature should not be an issue. The heat in a few drop of liquid is quickly lost to the surrounds as it lands on the glass prism. Whereas using a hydrometer you have to either cool your wort first or measure the temperature and adjust the gravity reading accordingly.

There is no reason why you shouldn't get consistent, accurate results. To be straight up, my first reaction is to suggest that problems using a refractometer might be a variant of the PEBKAC issue.

Happy Analysing,

Keith

 

[goatherder]

There is no reason why you shouldn't get consistent, accurate results. To be straight up, my first reaction is to suggest that problems using a refractometer might be a variant of the PEBKAC issue.

Happy Analysing,

Keith

I have no doubt that you are correct in the source of my problems Keith. I might pull the refractometer out next brew and follow your tips, see if it's any better.

 

[lucas]

You gotta remember its a piece of groovy scientific equipment and you need to both use it properly and look after it. Calibrate it before use, make sure the prism is entirely covered by your sample, dont have floaties in your sample, rinse it with clean water after use, dry the glass prism before storing it, blah, blah, blah.

I think another important thing to to dry the prism before you attempt to use it. if it's not dry you're diluting your sample

 

[Barge]

Another thing to be aware of, if using one like mine, (it's a 0-32 Brix, probably el cheapo) is that the instructions say to recalibrate after 30 mins. So on brew day you may need to calibrate a few times to get consistent results.

 

[domonsura]

I've never heard of having to re-calibrate a refractometer every 30 mins, are you sure the instructions aren't just in 'engrish' and that instruction is an error in translation?
If I had to recalibrate mine regularly during the brewday I would proably bin it!
Here are a couple of the tips I would probably give;

* make a point of cleaning the lense/tip with a clean damp tissue/cloth after every sample, this will keep your refract' in good condition, and mean that your sample is neither diluted by water nor contaminated with residual sugars from the last sample. It also means you won't come back to find it congealed with sugar & stuck to the foam in the bottom of it's case at your next brewday...

* when you take your sample, if using a pipette - make sure you 'rinse' it in your main wort, to make sure that there is not liquid/sugars inside to throw your reading out - ie: don't comtaminate your sample before it even gets to the refractometer.

* don't take sample after sample in quick succession, even with an ATC model, unless you cool your wort first because repeated samples of hot wort will heat up the lense, and will make your readings inaccurate. (From memory, the warmer mine gets, the lower the readings get, that would be something to do with the extra heat on the lense would cause the sample particles to expand/spread out more on the lense, and therefore less refraction would take place as the light passes through the sample=lower reading.)

These are the things I do, and I get good consistent readings. Of course there are the 'user related' discrepancies, but they are nothing to do with my instruments..... :lol:

 

[BrissyBrew]

* don't take sample after sample in quick succession, even with an ATC model, unless you cool your wort first because repeated samples of hot wort will heat up the lense, and will make your readings inaccurate. (From memory, the warmer mine gets, the lower the readings get, that would be something to do with the extra heat on the lense would cause the sample particles to expand/spread out more on the lense, and therefore less refraction would take place as the light passes through the sample=lower reading.)

good advice

also dont forget for beer, especially darker beer you need to calibrate your refract to the beer, all those dark grains resulting in darker beers does effect refraction. Oh and post ferment readings with a hefe forget it.

 

[warrenlw63]

Warren, one of the advantages of using a refractometer is that the temperature should not be an issue. The heat in a few drop of liquid is quickly lost to the surrounds as it lands on the glass prism. Whereas using a hydrometer you have to either cool your wort first or measure the temperature and adjust the gravity reading accordingly.

Hey Keith.

Wasn't actually the temperature of the sample that concerned me as I know at that size it should cool to 20 degrees quite rapidly.
It's more the issues of taking a small sample of near boiling liquid to put on the prism. I was questioning how much higher will the sample read due to the minute amount of evaporative loss from the small wisp of steam you see when the sample hits the lens?

I'm thinking it would be safer to cool the sample before putting it on the lens to avoid small amounts of evaporation? I still think a refractometer is worth it's weight in gold for fly spargers looking for quick turnaround on sparge cutoff points though.

Now I batch sparge mine virtually sits in mothballs. I only use it to check the SG of my yeast starters.

Warren -

 

[Ross]

I'd be lost without my refractometer, especially when doing higher/lower gravity brews where your grain efficiency can vary quite a bit from the norm. The preboil gravity is my most important reading of the day, as this is where i make any adjustments neccesary to achieve the desired end result. I take a 1/2 tsp sample at the beginning of the boil, let it cool for a couple of minutes & then measure. I do this twice, to rule out a rouge reading & find the results very consistant.

cheers Ross

 

[mika]

I'm with Ross, I take a sample in the little pippette type thingo. Let it sit and after 5mins or so take a reading. Have noticied that if you take a reading quickly and then come back to it again later, the later sample with read slightly higher.
Have wondered as Warren has if this is due to the water evaoprating and the sample becoming higher gravity, or a darkening of the wort being exposed to sunlight, the pull of the moons gravity or whatever.
I've kinda learned to accept these little issues and get on with brewing beer.

 

[Barge]

are you sure the instructions aren't just in 'engrish' and that instruction is an error in translation?

The instructions say 'liquid and speciment should be under the same temperature. If the temperature varies greatly, the null point should be adlusted once per 30 minutes.'

To be honest, I'm not sure what that means. I assumed it meant that if sampling hot liquids that you need to recalibrate but I dunno.

also dont forget for beer, especially darker beer you need to calibrate your refract to the beer, all those dark grains resulting in darker beers does effect refraction.

BrissyBrew: How do you take into account darker wort when calibrating. Do you use Adelaide water

 

[domonsura]

The instructions say 'liquid and speciment should be under the same temperature. If the temperature varies greatly, the null point should be adlusted once per 30 minutes.'

To be honest, I'm not sure what that means. I assumed it meant that if sampling hot liquids that you need to recalibrate but I dunno.

Well, I would call that 'engrish'. I can only guess at what they might mean, and say - calibrate you refractometer with water at the same temperature as your specimen you are wanting to test, ie: calibrate with water @ 20 deg, test your samples when cooled to ~20 deg.
The 30 minute thing is beyond me, unless they mean if your sample temperatures are all over the place you may need to recalibrate accordingly?
Bypass the engrish advice by making sure you let your wort sample cool as Ross says, that's what I do mostly.
Can I ask if your refract is an automatic temp compensating (ATC) model?

 

[domonsura]

And as I said before, the reason for lower reading at higher temps, is that a warmer liquid will expand (becomes less dense) over the lense more, and refract light less. So when it's cooled a bit, it becomes more dense, and refracts more light, so cooling the sample down is important.

 

[PostModern]

cooling the sample down is important.

An easy way to do that is to swish the bulb of the pipette in a bucket of water or sanitiser while holding your finger over the opening. Takes only a couple of seconds to bring the temp down on such a small sample.