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Old 01-22-2014, 01:00 PM   #1
b-boy
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Default Weird Refractometer Issue

I brewed a batch of Imperial Red Ale in my garage yesterday. It was 7F outside. I'm not really sure what I was thinking, but I was off work and I had the itch to brew. My water hose froze within about 15 minutes, but I got through it somehow.

However - I had a weird issue with my refractometer. I have a fairly new ATC refractometer. It's not super high-end, but it's not a cheapie either.

My pre-boil gravity reading was 15 Brix (~1.060). I boiled for 60 minutes and added 1 lb of corn sugar to the recipe at flame-out. I boiled off about 1.5 gallons of liquid. My post-boil reading was 19 Brix (1.078). I was fairly happy because my predicted target was just slightly higher.

Once I cooled my wort to about 65F, I re-took a reading. I was surprised because I got 15 Brix. I took another sample and got 15 Brix again.

It didn't make any sense, so I'm assuming equipment problems. I re-tested my refractometer with water. It checked out, but I did this after it was brought inside and it had warmed up a bit.

Anyone have an idea of what happened here? Is it a temperature thing? Even with the ATC, is there a set temperature range (min-max) to use a refractometer? Is 7F a little too cold for an accurate reading?

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Old 01-22-2014, 01:05 PM   #2
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ATC refers to a bi-metal portion of the frame holding the scale. As the temperature changes, the frame moves slightly to compensate for the change in temperature. The sample size is so small that it will equilibrate to the temperature of the device within seconds.

As to 7°F, that may be the problem. Asking the refractometer to adjust to such a huge range is really asking a lot.

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Old 01-22-2014, 01:14 PM   #3
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This makes sense to me. It pretty much validates my thoughts. Since my initial samples were quite hot, I guess the refractometer was able to compensate. I'm thinking all my reading are suspect now. Oh well - It's still beer.

I was very surprised that my mash tun held my mash temperatures as well as it did. I only had a 2F drop in 60 minutes.

I'm waiting until at least March before I attempt another brew-day. Brewing Jan-Feb in Buffalo is just not a good idea.

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Old 01-22-2014, 01:21 PM   #4
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Wussie!

Get out there and brew, man!

Just leave the refractometer inside...

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Old 01-22-2014, 01:33 PM   #5
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Quote:
Originally Posted by ianw58 View Post
Wussie!

Get out there and brew, man!
says the guy from California......

On the plus side, my wort went from 212F to 65F in about 5 minutes.
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Old 01-22-2014, 04:32 PM   #6
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Im in nc and brewed in the shed out back last week in the snow and -13° with the wind chill. And I only lost 3 deg in my tun. I was shocked. Love cold brew days.. more beer needed to keep warm :sly: anyways as for your question my buddy always Has the same problem with his refrac during the cold months so we just use hydros till it warms up.

Sent from my SPH-L710 using Home Brew mobile app

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Old 01-22-2014, 04:42 PM   #7
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There are several reasons that refractometers should not be used in brewing (except where they are properly calibrated to the particular beer being brewed) most of which derive from the fact that the refractive indices of the sugars encountered in worts do not follow the refractive indices of the sucrose solutions on which the Brix scale is based but probably number two is that the ATC 'curve' is based on the variations of sucrose RI with temperature which is not the same as the RI change with temperature for the sugars in wort. If you are going to use a refractometer be sure to use it at the temperature for which it was calibrated. The 'ATC' in the handheld optical devices is very crude. One can expect deviations to be less than 2 Bx if this is done. I guess OP's experience is a data point for what can happen when ATC is put to work.

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Old 01-22-2014, 06:54 PM   #8
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Going forward I'll guess I'll just take my samples and save them for indoor testing later. That should alleviate the problem.

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