Reading A Refrac.

[Hashie]

G'day all, just want to make sure I'm doing this right. Before I get too excited about good efficiencies.

What I am doing is as follows;

Take a sample with supplied pipette, place a few drops onto the refrac. window, close the cover, allow to cool to 20C, take a reading. At this point the reading can be quite fuzzy (hard to see a definite line between the white and blue), so what I am doing is opening and closing the cover. This gives me a definite line of separation making it easy to read. Is this ok or will it affect the readings I am getting?

 

[KillerRx4]

Try to get as clear a sample as possible, sometimes its impossible.
Its the solids in the sample giving you the blur.

 

[Screwtop]

G'day all, just want to make sure I'm doing this right. Before I get too excited about good efficiencies.

What I am doing is as follows;

Take a sample with supplied pipette, place a few drops onto the refrac. window, close the cover, allow to cool to 20C, take a reading. At this point the reading can be quite fuzzy (hard to see a definite line between the white and blue), so what I am doing is opening and closing the cover. This gives me a definite line of separation making it easy to read. Is this ok or will it affect the readings I am getting?

I allow the sample to cool in the bulb of the dropper before putting a couple of drops onto the lens of the Refractometer.

Screwy

 

[Cortez The Killer]

Here is a chart you might find useful

http://www.aussiehomebrewer.com/forum/inde...st&p=330379

Cheers

 

[Hashie]

I have noticed small bits of grain on the lens, it's not easy to get a clear sample.

Will try letting the sample cool in the pipette next brew, see how that goes.

As for today's brew it all went well. According to beersmith I hit 84.34% Brewhouse efficiency, hence the need for clarity on sampling before I go getting too excited

 

[RobB]

I try to cool the sample before putting it on the refractometer. When I first started using it, I would put a couple of drops of wort on the glass at mashout temperature. However, I noticed that the drops would immediately evaporate around the edges since it was such a small volume at quite a warm temperature. So I was inadvertently concentrating my sample and getting an artificially high reading.

These days I take a larger sample (about a teaspoon) and drop it into a steel measuring cup which I keep in the freezer. The wort cools almost instantaneously and then I take my sample drops.

 

[Ducatiboy stu]

If your sample is cloudy, you will get a fuzzy reading

 

[drsmurto]

Point the refractometer at a source of light.

I scoop out a sample with my 'mash paddle' which after the demise of my coopers spoon looks suspiciously like a soup ladle.... and allow it to cool before taking a reading.

 

[Fents]

after the demise of my coopers spoon looks suspiciously like a soup ladle....

ahh you lost yours in battle too. mine had been fighting for over 4 years on the front line then one day in the trenches....sssssnap!

 

[Hashie]

Thanks for the replies.
Looks like cooling before putting onto the refrac is the way to go.

 

[Frank]

I don't bother with the eye dropper. Just dip the whole end into your sample. As you are sampling pre boil, or during boil it is fine to throw the sample back into your tun. Just don't return the sample once you are taking from the fermenter. Refractometers are water proof, rinse under the tap once you have finished.

 

[Batz]

I have to ask this,you know you can focus the thing ? I did know someone complaining about a fuzzy reading who didn't realize this.

Batz

 

[Hashie]

^ Sure Batz, I have it in focus

 

[therook]

If the Refractometers are ATC i didn't think temp what a problem?

Rook

 

[fraser_john]

Clarity of sample and a strong light source is the best solution to a clean line. Plus the focus ring! All of these mentioned in the above thread.

 

[Frank]

If the Refractometers are ATC i didn't think temp what a problem?

Rook

Yes, and no. If your sample is too hot in can start to evaporate on the prism and give you a false higher reading.

 

[ikern]

I put a couple of drops on the lens and then close the cover ASAP to minimise evap, I then leave the refrac on the bench with the cover down to cool before taking a reading.

For those that leave the sample in a seperate container to cool before placing on the refrac, wouldn't you be getting evap anyway?

Cheers :beer:

Soz

 

[therook]

I put a couple of drops on the lens and then close the cover ASAP to minimise evap, I then leave the refrac on the bench with the cover down to cool before taking a reading.

For those that leave the sample in a seperate container to cool before placing on the refrac, wouldn't you be getting evap anyway?

Cheers :beer:

Soz

Excellent point Soz

 

[TidalPete]

I put a couple of drops on the lens and then close the cover ASAP to minimise evap, I then leave the refrac on the bench with the cover down to cool before taking a reading.

For those that leave the sample in a seperate container to cool before placing on the refrac, wouldn't you be getting evap anyway?

Cheers :beer:

Soz

Ditto. I leave the refrac & sample to cool for a few minutes before taking the reading.

TP :beer:

 

[RobB]

For those that leave the sample in a seperate container to cool before placing on the refrac, wouldn't you be getting evap anyway?

A slightly larger sample in a container will evaporate less than a smear on the prism since it has a higher ratio of volume to surface area. Plus, I drop my sample into a cup which I've just taken out of the freezer, so it chills to room temperature almost instantly.

Maybe if you're quick enough to close the cover you won't get significant evaporation, but I found I was getting artificially high readings by by dropping hot wort on the prism.

And +1 for pointing the end at the light, it really makes a big difference.