Author Topic: Refractometer Calibration  (Read 2398 times)

Offline case thrower

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Re: Refractometer Calibration
« Reply #30 on: November 26, 2014, 05:57:51 PM »
And someone asked in another thread why you don't like Chico.  What are your thoughts on Groucho and Harpo?

"Je suis Marxiste, tendance Groucho."
[/quote]

Oh, man, you'll have to translate that for me.  If it isn't in English, it might as well be in ancient Egyptian hieroglyphs.

And yeah, I do see about a 5 degree variation from top to bottom.  I'm stirring the whole time the grains are going in and then I continue till I'm sure there aren't any dough balls.  Put the thermometer in, put the lid on and walk away for a minute or two.  Then I check the temp and start the timer.
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Offline archstanton

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Re: Refractometer Calibration
« Reply #31 on: November 26, 2014, 08:40:57 PM »
Why can't you get an accurate gravity measure until the boil starts?

Like Denny said, the wort will start out stratified (unless it's a no-sparge beer), and no reasonable amount of stirring will get it well-mixed. This could actually be a case where a hydrometer would give better results, due to the larger sample size.

In practice I just measure my first and second runnings with the refractometer and math the pre-boil gravity.


I have never seen an issue with this, pulling from the top and bottom of my kettle as yielded the same results. Wouldn't this theory make it impossible then to use priming sugar to carbonate equally? If it just won't mix then all of your bottles would have different carbonation?

Offline HoosierBrew

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Re: Refractometer Calibration
« Reply #32 on: November 26, 2014, 08:58:04 PM »
Why can't you get an accurate gravity measure until the boil starts?

Like Denny said, the wort will start out stratified (unless it's a no-sparge beer), and no reasonable amount of stirring will get it well-mixed. This could actually be a case where a hydrometer would give better results, due to the larger sample size.

In practice I just measure my first and second runnings with the refractometer and math the pre-boil gravity.


I have never seen an issue with this, pulling from the top and bottom of my kettle as yielded the same results. Wouldn't this theory make it impossible then to use priming sugar to carbonate equally? If it just won't mix then all of your bottles would have different carbonation?

The turbulence of the boil (as well as the later turbulence of fermentation on the beer) thoroughly mixes the varying densities of mash runoff so that you have a homogenous mixture to prime.
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Offline archstanton

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Re: Refractometer Calibration
« Reply #33 on: November 26, 2014, 10:16:23 PM »
Why can't you get an accurate gravity measure until the boil starts?

Like Denny said, the wort will start out stratified (unless it's a no-sparge beer), and no reasonable amount of stirring will get it well-mixed. This could actually be a case where a hydrometer would give better results, due to the larger sample size.

In practice I just measure my first and second runnings with the refractometer and math the pre-boil gravity.


I have never seen an issue with this, pulling from the top and bottom of my kettle as yielded the same results. Wouldn't this theory make it impossible then to use priming sugar to carbonate equally? If it just won't mix then all of your bottles would have different carbonation?

The turbulence of the boil (as well as the later turbulence of fermentation on the beer) thoroughly mixes the varying densities of mash runoff so that you have a homogenous mixture to prime.

I think you are misunderstanding me, I mean the priming sugar and the beer itself won't mix evenly because they are not boiled, only stirred and then bottled. I haven't bottled in years but when I did I didn't notice a difference among the bottles.

Offline HoosierBrew

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Re: Refractometer Calibration
« Reply #34 on: November 26, 2014, 11:19:50 PM »
archstanton - I get what you're saying. I just feel that it's very easy to stir a small amount of simple syrup into 5 gallons of beer that is ALREADY of equal density and temperature after boiling and cooling. IMO what is much tougher is to combine large volumes of liquid, each of different densities ( as runoff gravity drops) AND temps into a homogenous mixture by hand. Here is where boiling helps IMO. My refractometer preboil readings were all over the place until I took the advice of several here to take a reading a couple minutes into the boil.
Jon H.

Offline hopfenundmalz

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Re: Refractometer Calibration
« Reply #35 on: November 27, 2014, 12:51:48 AM »
As a an engineer who had to calibrate his transducers every day, I have a comment on refractometer calibration.

Using your water of choice, distilled is often recommended, use that and set to zero Brix. You have zeroed the instrument. What about the gain? For a refractometer, you can check a 10% sugar solution (~1.040) by mixing water and sucrose, instructions are on the net. You might be surprised that the reading is off, I was. Then I tried 15 Brix and it was dead on. Diluted that to 10%, and it was off the same amount.

Adjusting the zero does not give you the gain (slope), and checking the gain at multiple points will show you if your instrument in linear. One learns this from every day practice over the years (until you are no longer doing hands on work).
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Offline archstanton

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Re: Refractometer Calibration
« Reply #36 on: November 27, 2014, 01:13:23 AM »
archstanton - I get what you're saying. I just feel that it's very easy to stir a small amount of simple syrup into 5 gallons of beer that is ALREADY of equal density and temperature after boiling and cooling. IMO what is much tougher is to combine large volumes of liquid, each of different densities ( as runoff gravity drops) AND temps into a homogenous mixture by hand. Here is where boiling helps IMO. My refractometer preboil readings were all over the place until I took the advice of several here to take a reading a couple minutes into the boil.

I see. Next time I have a numbers problem, I will have one more thing to check out.

Offline a10t2

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Re: Refractometer Calibration
« Reply #37 on: November 27, 2014, 04:50:16 PM »
I think you are misunderstanding me, I mean the priming sugar and the beer itself won't mix evenly because they are not boiled, only stirred and then bottled. I haven't bottled in years but when I did I didn't notice a difference among the bottles.

I don't do much bottling either, but from forum threads I've seen it seems like people do have trouble with the beer and priming solution not being thoroughly mixed.
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Offline BrewingRover

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Re: Refractometer Calibration
« Reply #38 on: November 27, 2014, 05:07:00 PM »
Why can't you get an accurate gravity measure until the boil starts?

Like Denny said, the wort will start out stratified (unless it's a no-sparge beer), and no reasonable amount of stirring will get it well-mixed. This could actually be a case where a hydrometer would give better results, due to the larger sample size.

I've measured the gravity from the top of the tun in a no-sparge beer, and it was significantly lower than the reading I took just after the boil started. I assume it's the same thing with the heavier sugars sinking to the bottom.
« Last Edit: November 27, 2014, 05:09:36 PM by BrewingRover »
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Offline ranchovillabrew

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Re: Refractometer Calibration
« Reply #39 on: November 28, 2014, 02:42:19 AM »
I think that you should calibrate with your regular brewing water ( tap, well,  ro,  distilled) since we aren't really interested in true sg but in the contribution of our extract over the initial sg of our water right?
- Charles

Offline archstanton

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Re: Refractometer Calibration
« Reply #40 on: November 28, 2014, 04:17:46 PM »
I think you are misunderstanding me, I mean the priming sugar and the beer itself won't mix evenly because they are not boiled, only stirred and then bottled. I haven't bottled in years but when I did I didn't notice a difference among the bottles.

I don't do much bottling either, but from forum threads I've seen it seems like people do have trouble with the beer and priming solution not being thoroughly mixed.

Yes that is possible. Usually though the problems are in getting the correct amount of carbonation not in uniform carbonation.

Also with your theory it would not be possible to get an accurate reading form the first runnings as the amount of sugar in the mash is increasing until 100% conversion it met. The second runnings would encounter the same issue as you would be adding water to what is left of a wet sugar and grain mixture. Without boiling neither would be uniform enough to get an accurate reading. You certainly could not create mathematical model based on such inaccuracies, like a batch sparge calculator for instance ;-)

Offline BUBBA LOU BREWERY

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Re: Refractometer Calibration
« Reply #41 on: December 01, 2014, 12:04:17 AM »
The cheeper refractometers like the atc ones are unreliable. I know this first hand due to being in the beverage repair business for over 10 years. I have found that the atago refractometers are durable and stay calibrated, they are a bit more money but worth it. Www.atago.net

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Re: Refractometer Calibration
« Reply #42 on: December 01, 2014, 01:18:05 AM »

Adjusting the zero does not give you the gain (slope), and checking the gain at multiple points will show you if your instrument in linear. One learns this from every day practice over the years (until you are no longer doing hands on work).

What good is the refractometer if the gain is not linear?  I would imagine that really throws off the FG calculations too.  I wonder if that is why every model for determining FG is different: they all used their own variable refractometer.

Is there a solution?  Maybe buy a better refractometer?  Or is this a permanent flaw in the refraction through the prism? It seems odd that these tools have passed the test of time with wine, but they don't work with a standard curve using sucrose. 

Offline hopfenundmalz

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Re: Refractometer Calibration
« Reply #43 on: December 01, 2014, 01:51:16 AM »

Adjusting the zero does not give you the gain (slope), and checking the gain at multiple points will show you if your instrument in linear. One learns this from every day practice over the years (until you are no longer doing hands on work).

What good is the refractometer if the gain is not linear?  I would imagine that really throws off the FG calculations too.  I wonder if that is why every model for determining FG is different: they all used their own variable refractometer.

Is there a solution?  Maybe buy a better refractometer?  Or is this a permanent flaw in the refraction through the prism? It seems odd that these tools have passed the test of time with wine, but they don't work with a standard curve using sucrose.

Solution?

Buy a good one. Avoid dropping it - as I have done more than once! I must say that I have only broken 1 hydrometer in 22 years, so I have that going for me, which is nice.

It does give a quick check of the gravity, so it is expedient.
Jeff Rankert
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Re: Refractometer Calibration
« Reply #44 on: December 01, 2014, 06:45:42 PM »
What do you recommend as a good one?