Reading a refractometer; clear line with distilled water; fuzzy line with beer

See the pictures (sorry for crappy iPhone pics). Left one is with distilled water and the right one is with a FBS clone that has been in primary for 12 days. I'm trying to ensure it's done before transferring to secondary (to add more coffee). I know the alcohol will screw up the number, so it's not accurate, but I thought I could tell if it was done using a refractometer. True or not true? Is the alcohol screwing up the reading? How would you read that?

I'd say 10.0 Brix. With mine, the longer I look at it the fuzzier it gets.

LOL. Should it be a clearer line though? Is it because of all the "stuff" in there? I'm pretty sure my APA wasn't that fuzzy.

I was reading a smidge lower than 10 brix, but 10 is about what I got 2 days ago. I'm hoping it's done because it's already finishing a little lower than I was expecting based on what other people were reporting after making this beer (closer to 1.030). I did do a hydrometer reading 2 days ago, but not today and it was 1.020. Beersmith estimates 1.022, so I guess I'm not that far off. I was expecting higher though since I think I mashed at a higher temp than I should have. I was having thermometer issues and it was my first BIAB.

Nice pictures.

Us over on WortMonger's pressure fermenting thread have to de-gas the sample, of CO2 before a reading. Try putting a little in a canning jar with a lid and shake it. Maybe that's it.

Sometimes a get a fuzzy line, very frustrating

Thanks. I'll try that. I did read it one more time and I let it sit for a couple minutes and the line was clearer.

There is probably no appreciable co2 in your fermenter to skew a reading. I got a fuzzy reading my last time, last week, no matter how long I let that bugger sample sit out.

It's the alcohol. Alcohol changes the way light refracts and since that is what a refractometer reads, they are hard to read and inaccurate once fermentation occurs.

Yooper said:

It's the alcohol. Alcohol changes the way light refracts and since that is what a refractometer reads, they are hard to read and inaccurate once fermentation occurs.

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This.

Thanks. I was still hoping I could use it to tell when fermentation was complete.

--deleted. wrong thread. --

OK, here's what I meant to write. This damn cold is not helping the thought processes.

mtnagel said:

Should it be a clearer line though? Is it because of all the "stuff" in there? I'm pretty sure my APA wasn't that fuzzy.

...I was having thermometer issues and it was my first BIAB.

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Ditto, nice images. They could be used for teaching.

I also notice fuzziness while reading the wort and the final fermented wort. It is probably because there are many compounds in there with different refractive indexes. It was not as fuzzy when I made a low alcohol beer, again probably because there was less stuff in there.

Temperature fluctuations with BIAB - I have also had problems chasing the proper mash temperature and have not entirely resolved it. Perhaps this info will help.

I think it is because of the method of reading temperature and not that the mash temp changes so quickly. I find the glass thermometer reads more consistently when the cold grain is stirred in thoroughly, the thermometer is inserted into the center, and I leave the pot covered for a few minutes. Then I uncover the pot and read the temperature very quickly. I was surprised how much temperature variation there is from top to bottom of the grain and how quickly the top grain cooled off when the lid was removed. Also, how fast the thermometer cooled off when it was removed for a reading.

For my next BIAB batch I will add the grain at the calculated strike temperature, stir it well, insert the thermometer, cover it, and leave it the heck alone for 5 minutes. Then pull and read the thermometer quickly.

BIAB is usually done in an uninsulated pot instead of a nice, cozy mash tun. If you use the full 7 gallons for a 5 gallon batch, the large heat mass will better maintain temperatures.

Yooper said:

It's the alcohol. Alcohol changes the way light refracts and since that is what a refractometer reads, they are hard to read and inaccurate once fermentation occurs.

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Mine is pretty fuzzy when i'm brewing. No alcohol there.

Try using a small flashlight and move it around the prism. I can usually find a sweet spot to get a decent reading.

To the OP, mtnagel:

Please see my 4 photos dated today, 4/14/13, which shows that you can confidently use your refractometer for reading your samples anytime during fermentation and for final gravity readings.

Thanks, nice pictures.

I have the same problem when making wine. Just turn the refractometer upside down and it should clear up the fuzzies. Just give a few seconds.

1MadScientist said:

To the OP, mtnagel:

Please see my 4 photos dated today, 4/14/13, which shows that you can confidently use your refractometer for reading your samples anytime during fermentation and for final gravity readings.

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How does that picture show that " that you can confidently use your refractometer for reading your samples anytime during fermentation and for final gravity readings"?

It shows you got a clear line, but the laws of physics say that the reading will not be correct. Even though it is possible to get a correct reading occasionally, you cannot get true repeatable results reading a refractometer when alcohol is present. The laws of physics, unlike civil laws cannot be broken on occasion.

How did you take those pictures?

Did you see the screenshots of the online correction calculators showing exactly what he got with his hydrometer?

Naturallight16oz said:

Mine is pretty fuzzy when i'm brewing. No alcohol there.

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Most have an eye-piece that can be adjusted like a telescope/binoculars for adjusting to get a clear image.

mtnagel said:

Did you see the screenshots of the online correction calculators showing exactly what he got with his hydrometer?

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Doh, missed them. So he meant to say you can get a reading that can be used to calculate the correct numbers. This is correct, but with the refractometers most of us use, it can be hard to get the reading as clear as he has, so there is a lot of guess work on the numbers for most people.

If you do manage to get a clear reading, then yes you can use the formula for adjusting.

Yep. Agreed based on my testing on like 2 batches

Honestly, if I'm off by +/- 0.002 or 0.003 I'm not going to sweat it. Maybe 1% alcohol difference. I don't really care. I just wanted to know it was done and it was okay for that. And I will use it for pre-fermentation now that I got into BIAB.

Yooper said:

It's the alcohol. Alcohol changes the way light refracts and since that is what a refractometer reads, they are hard to read and inaccurate once fermentation occurs.

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This x 2

Use a refractometer for OG and a hydrometer for FG. Alcohol content makes refractometers inaccurate.

Morebeer had a spreadsheet on their site to correct fermented refractometer samples and although I don't rely on my refractometer for FG readings the few times I tried it it was right on with my hydrometer sample. No blurry lines either.

Though alcohol will distort the reading, it shouldn't make it impossible to get a reading. With my refractometer, I have no problem getting a sharp line with wort, both before and after fermentation. If you're consistently getting a blurry line like this, it's likely caused by solids in the liquid that are preventing a good, clean contact between the stage and the plastic cover.

sorry for digging, but can you correct me? About 2 pictures from 1st post.
1.120 is showed that it is more than 30% Brix where when you use calculator or whatever 30% Brix is around 1.130. What is lying here?