weird results measuring OG with refractometer

[Nick JD]

I just took a reading from the Boh Pils I'm currently drinking. Got a very clear line, so it's not the alcohol that blurs the line when taking fermentation readings, it's the crud.

And yup - that's an exceedingly cheap refrac. HA! Started at 1.050, finished at 6 bricks high ... calc says 1.007. Dry, dry dry. Mmmmm.

 

[nala]

Do people usually get "sharp defined lines" with refractometers? How "sharp" are we talking here? :huh:

Mine has always been blurry, at least blurry enough that I basically flip a coin to decide between two neighbouring 0.2 brix increments. I'm not entering any competitions or anything so I've never worried THAT much about it.

Quick Google image search, mine tends to look like this.

How would you guys read that result there? I would probably say, 9.2? Maybe 9.4?

There are various types of refractometers, yours appears to be very crude.
The scale on yours is too course and it makes it difficult to make an assessment.
The one that I use is graduated in increments of one degree, I purposely bought a beer refractometer which has an upper scale of 1.030 I have never experienced a problem and get readings which are in the ball park of what they should be, one of the best purchases that I have made.

 

[felten]

Do people usually get "sharp defined lines" with refractometers? How "sharp" are we talking here? :huh:

Mine has always been blurry, at least blurry enough that I basically flip a coin to decide between two neighbouring 0.2 brix increments. I'm not entering any competitions or anything so I've never worried THAT much about it.

Quick Google image search, mine tends to look like this.

How would you guys read that result there? I would probably say, 9.2? Maybe 9.4?

Hard to tell in the pic..

I usually (if I'm not lazy) take a sample in a pipette and leave it to settle out. All the crud will drop to the bottom and you can squeeze it out before taking a reading.

Have you tried fiddling with the twist-zoom thing to make it easier to read?

 

[Edak]

If it is a cheap refrac like the one I used to use then you try to adjust the focus for the blue and then the scale goes out of focus. POS went into the bin and I got a digital refrac the same as the one little creatures use in their brewery.

 

[slash22000]

I'm told digital refractometers don't work with "coloured liquid"? In other words, all beer? What model are you using, Edak?

 

[Edak]

I am using an OPTI+, definitely for beer...

http://www.bellinghamandstanley.com/general_pdfs/literature_page/OPTiPlus.pdf

 

[slash22000]

Am I googling this incorrectly or do they cost something like $800 ... ?

 

[Bribie G]

Nick how do you take the photo?

 

[iralosavic]

Am I googling this incorrectly or do they cost something like $800 ... ?

$450 shipped from UK by my Googlez. Awesome device, but too hard to justify for most home brewers, I imagine.

 

[BobtheBrewer]

Well, now I know why I have had a problem reading my refractometer. Being right handed I naturally use my right eye. Went to the optometrist today and I'm told that I have a cataract on my right eye that needs urgent attention, and one growing on my left eye, and that I shouldn't be driving. That last bit stirred up the missus who prefers not to drive. Thankfully it shouldn't affect my brewing, I'll just change eyes.

 

[Nick JD]

Nick how do you take the photo?

Shove the pointy bit up to the beer telescope after turning the flash off, point randomly at the light source and when you see the picture in the screen and hit the button.

Have to hold the camera lens about 10mm off the refrac aperture

.

 

[iralosavic]

Well, now I know why I have had a problem reading my refractometer. Being right handed I naturally use my right eye. Went to the optometrist today and I'm told that I have a cataract on my right eye that needs urgent attention, and one growing on my left eye, and that I shouldn't be driving. That last bit stirred up the missus who prefers not to drive. Thankfully it shouldn't affect my brewing, I'll just change eyes.

I often get my missus to check refractometer readings. Because she doesn't understand the necessary sensitivity of the reading, she spends ages getting it down to 1.XXXX for me. My left eye vision is ok, but I feel just as retarded using it in isolation as I do using my left arm to throw a ball. I hope things go well in relation to getting the cataracts sorted. My issue is a severe astigmatism (around 5% vision), which has no cure.

 

[Nick JD]

I shoot a compound bow with a 4x mag target sight in it.

Can usually get an X with the refractometer.

 

[Edak]

$450 shipped from UK by my Googlez. Awesome device, but too hard to justify for most home brewers, I imagine.

When one used to work for the distributor they get good discounts

 

[WitWonder]

False. You can read fermenting gravity with a refractometer, you just need to use a calcuator program to fix the value to accommodate for the alcohol etc. You can find about 25,000 of them all over the net.

He is, of course, exaggerating. There are precisely 24,884 such calculator programs on the internet as of todays date. :huh:

 

[verysupple]

I've only ever used a hydrometer and always assumed a refractometer was more accurate (as long as you accounted for temperature and alcohol content). After reading this thread I'm wondering if my assumptions were wrong.

As a physicist, I understand that when you take a hydrometer reading post innoculation, you are only measuring the total specific gravity (not accounting for the fact that alcohol is present and lowering the total SG - ethanol being less dense than water). This is fine as that is how apparent attenuation is defined.

If BribieG's problem arose from particulate matter settling, this would also be a problem using a hydrometer. If his problem is due to something else, then a hydrometer should give a consistent reading.

Maybe BribieG could take refractometer and hydrometer readings next time and update us.

Of course it's Friday night and I've had a few, so if I'm talking bollocks, please correct me.

 

[Bribie G]

I'm thinking of getting a hydrometer again, as I'll be doing ales at ambient from now till about October. In SEQ I could nearly always pick when the fermentation had finished, as the garage rarely got below 18 even in the Winter, but since moving to a cooler area I could trip myself up without a hydro.

 

[PeteQ]

I use my crappy refractometer throughout the mash and boil quite a few times on a brewday and if i play around with the flap a few times (yes you heard right) after dropping wort onto the glass it can jump up to 10 points. Give it another go, leave it to cool and it might jump 1 or 2 points??

If you haven't seen this before give it a go and let us all know what your results are... Maybe my refractometer is super crappy?

 

[MaltyHops]

I use my crappy refractometer throughout the mash and boil quite a few times on a brewday and if i play around with the flap a few times (yes you heard right) after dropping wort onto the glass it can jump up to 10 points. Give it another go, leave it to cool and it might jump 1 or 2 points??

If you haven't seen this before give it a go and let us all know what your results are... Maybe my refractometer is super crappy?

Could it be your sample is evaporating a little and hence concentrating the sugars on the refractometer?

 

[mmmyummybeer]

Are you testing you sample at 20C. I test during the boil but put a sample in the fridge to cool to around 20 before testing. My refract was a cheap ebay buy but seems pretty good. Even my 4 year old has picked it up and given me a accurate reading. Is great to be able to test during the boil.