Refractometer border is fuzzy

[J2W2]

Hi,

I found a post from a few years ago with a similar topic, but a different issue.

I've been using a refractometer for some time now. It's been working well, but yesterday and today when I used it, the blue/white border is fuzzy instead of being well defined like usual. I've tuned the eyepiece, and the scales are very sharp, but not the border.

I'm using it on a beer I brewed on Friday, and my initial reading had a sharp border. I also tested it today with distilled water, and the border was well defined and right on 0.

So, I'm wondering if the "newness" of the beer can be effecting it? I'm brewing a porter, and the sample I pulled was fairly cloudy. The blow-off tube is still fairly active, so I think the fermentation process is still pretty active as well (it's in a stainless steel brew bucket so I can't see it).

Has anyone else had a similar experience or have an idea what's causing this?

Thanks for your help.

 

[stpug]

Air bubbles between the crystal and clear plate will make the blurry line worse, as will a more cloudy sample. The clearer the sample the crisper the line. Also, if you rotate your eyepiece so you're looking at the scale upside-down then you will likely see a stronger definition of color difference as well as the line tends to get more crisp as well. At least this has been my experience with refracts.

 

[ChefRex]

I'll lift and drop the cover a couple times and it seem to clear mine, as stpug said bubbles.

 

[JosephN]

Yep agree with above statements. Mine usually happens with cloudy wort or wort with higher protein content.

 

[fun4stuff]

i find that i usually just need to look at a brighter light source and the line clears and becomes more defined

 

[J2W2]

Thanks for all the advice.

I can try lifting and dropping the cover next time if it's still fuzzy, but I've not had this issue before so I don't think that's the issue. Especially two times in a row since I haven't seen it before.

I'm leaning more toward the cloudy sample. I don't think I've taken one this early before (I generally give it a week). I'm trying to get an idea on where the fermentation is at so I can start raising the temperature.

stpug, I'll try the upside down trick as well. I'll just keep testing it and I'll see how it goes.

Thanks again for your help.

 

[govner1]

Take off your glasses if you wear them, focus !
Recalibrate w/ distilled water.

 

[jddevinn]

Get a digital, they aren't that much!

 

[greyghost]

Get a digital, they aren't that much!

Couldn't agree more. No more guessing. To the 10th.

 

[stpug]

Thanks for all the advice.

I can try lifting and dropping the cover next time if it's still fuzzy, but I've not had this issue before so I don't think that's the issue. Especially two times in a row since I haven't seen it before.

I'm leaning more toward the cloudy sample. I don't think I've taken one this early before (I generally give it a week). I'm trying to get an idea on where the fermentation is at so I can start raising the temperature.

stpug, I'll try the upside down trick as well. I'll just keep testing it and I'll see how it goes.

Thanks again for your help.

If you have a cloudy/yeast sample, you can pour it through a small patch of paper towel to serve as a filter. You only need a drop or two to come out the otherside since that should be plenty to get a reading. I usually have to do this with grape must but I'd imagine it would work the same on a cloudy beer sample (I can't think why it wouldn't work anyway). It will filter out most of the yeast and particulate matter leaving a clearer sample which will result in a crisper line.

 

[jddevinn]

Get a digital, they aren't that much!

I sound like I'm kidding but I'm not.... they are really cheap.

http://www.amazon.com/dp/B002NX0WHS/?tag=skimlinks_replacement-20

 

[tele_dirtbag]

Hi,

border is fuzzy instead of being well defined like usual. I've tuned the eyepiece, and the scales are very sharp, but not the border.

I'm using it on a beer I brewed on Friday

I always had this problem with my refractometer when I was taking a reading once the beer had started fermenting. I could be wrong, but I thought this is one of the downsides to using refractometers, the blurry line is a result of the alcohol that is now present in the beer?

 

[fun4stuff]

I sound like I'm kidding but I'm not.... they are really cheap.

http://www.amazon.com/dp/B002NX0WHS/?tag=skimlinks_replacement-20

Haha, that's 10x the price of non digital ones! http://www.amazon.com/gp/aw/d/B00CO9BX6U/ref=mp_s_a_1_10?qid=1456330687&sr=8-10&pi=AC_SX236_SY340_QL65&keywords=refractometer

Seriously guys- make sure there is no air bubbles and point it at bright light source.

 

[ajdelange]

No, the blurry line is the result of scattering of light by yeast, protein particles... Digital refractometers suffer from this too. The better ones will give you a warning when the transition is too broad.

 

[jddevinn]

No, the blurry line is the result of scattering of light by yeast, protein particles... Digital refractometers suffer from this too. The better ones will give you a warning when the transition is too broad.

This makes since. I should probably strain some of the next fermentation sample I take and see if it makes a difference

 

[Bobby_M]

I haven't seen it mentioned but blurriness is mostly caused by wide diffused light sources. Go somewhere where you have a single light bulb overhead and see how much clearer it actually is. Outside is the worst since light is coming from all directions. Inside with multiple fluorescent bulbs all over the place is not much better.

 

[augiedoggy]

I always had this problem with my refractometer when I was taking a reading once the beer had started fermenting. I could be wrong, but I thought this is one of the downsides to using refractometers, the blurry line is a result of the alcohol that is now present in the beer?

When alcohol is present the refractometer reading is just thrown off and a formula has to be used to determine the proper reading... The fuzzy line is from solids or bubbles in the sample as far as Ive ever been able to tell.. I use a hydrometer after the yeast is added myself rather than mess with the math of correcting the refractometer readings.

 

[greyghost]

I sound like I'm kidding but I'm not.... they are really cheap.

http://www.amazon.com/dp/B002NX0WHS/?tag=skimlinks_replacement-20

This one looks to be the same. I have been using one for over a year with no problems and is cheaper.
http://www.amazon.com/gp/product/B007Z4IN58/?tag=skimlinks_replacement-20

 

[ajdelange]

I haven't seen it mentioned but blurriness is mostly caused by wide diffused light sources. Go somewhere where you have a single light bulb overhead and see how much clearer it actually is. Outside is the worst since light is coming from all directions. Inside with multiple fluorescent bulbs all over the place is not much better.

I don't think so. They have to be able to work with light coming in from all angles. In the bench top Abbe design the illuminating prism is designed to insure light is coming in from all directions and these are similar though I can't find mine to check it out in more detail. What does spread the boundary that has not been mentioned before is that the refractive index of light depends on its wavelength and as sources cover a wide range of wavelengths the critical angle (which is what the instrument really senses) will vary and in white lite the boundary (between transmission and total internal reflection) will be broad. I think this is helped somewhat in the handheld instruments by limiting red and yellow light input (the field looks bluish as I recall). This can be compensated for by the inclusion of special (Amici) prisms in the telescope as is done in benchtop instruments but not is the handheld ones. Try looking at the blue north sky rather than the sun when outdoors and see if that helps.

The digital instruments don't suffer from this problem because the light source is a narrow band LED.

 

[Bobby_M]

At least try it before you poo poo my conclusion.

 

[ajdelange]

I would if I could find my 'analogue' refractometer and I didn't mean to poo poo your observation but rather said that I didn't think your explanation was correct because of the way these things are designed.

 

[J2W2]

Wow - a lot of activity since I last checked this post.

I sound like I'm kidding but I'm not.... they are really cheap.

Perhaps in the grand scheme of what I've spent on my hobby, but... My analog refractometer was "free" when I spent $100 at Midwest Supplies, which was easy because I picked it up when I was building my keezer (now there's a cheap project).

Overall I'm very happy with my refractometer; for me it's light-years ahead of using a hydrometer; using a wine thief to pull a large enough sample and then making a best guess around the bubbles, curved line, etc. Even with a more cloudy line on the refractometer I think I'm still getting a much closer reading.

jddevinn, you have caught my interest however. Is the model you show on Amazon the one you have, or are all digital refractometers basically the same as long as they are meant for beer/wine? Just a quick search on Amazon showed digitals from $114 to $800. Maybe some day when I have some cash burning a hole in my pocket (or when I hit the lottery).

Just a quick recap on my initial post. The oatmeal porter I'm working on is two-weeks old today. My starting Brix of 17 has settled out at 9.1, which is putting me right at my expected gravity of 1.015 and ABV of 7%. The refractometer border still isn't what I'd call sharp, but it's much better defined than it was early on. It's got another week in the primary and then three in the secondary with some vanilla beans, so I'll see how it looks when I take my final readings.

Thanks again for all the help!

 

[jrcrilly]

If you have a cloudy/yeast sample, you can pour it through a small patch of paper towel to serve as a filter.

That works well for me.

 

[jddevinn]

Wow - a lot of activity since I last checked this post.


jddevinn, you have caught my interest however. Is the model you show on Amazon the one you have, or are all digital refractometers basically the same as long as they are meant for beer/wine? Just a quick search on Amazon showed digitals from $114 to $800. Maybe some day when I have some cash burning a hole in my pocket (or when I hit the lottery).

The one that I linked is the one that I have. The green one linked by greyghost looks very similar, just another manufacturer and accuracy is stated as slightly different.

While I do still use a hydrometer the first time or two on a new brew to determine the "actual" final gravity I don't use it on subsequent brews of the same recipe.