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Refractometer Vs Hydrometer


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#1 hz3gzy

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Posted 23 February 2007 - 05:55 AM

Does anybody use a refractometer when checking their Brix? I am thinking about buying one. Is it more accurate than a hydrometer? Are there any disadvantages when using a refractometer? I would appreciate some feedback.

Thanks Russ

#2 Peter Lynch

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Posted 23 February 2007 - 06:44 AM

QUOTE (hz3gzy @ Feb 23 2007, 07:27 AM) <{POST_SNAPBACK}>
Does anybody use a refractometer when checking their Brix? I am thinking about buying one. Is it more accurate than a hydrometer? Are there any disadvantages when using a refractometer?
Russ, I use both. I wouldn't say a refractometer is any more accurate but it certainly is simpler. The handheld is most useful in field sampling when crushing enough fruit to use a hydrometer is impractical. Also nice to get a quick reading on a must especially when the juice sample is foamy making a hydrometer reading difficult. Disadvantages can be that the small sample size sometimes requires several samples to be measured and averaged to get a representative & accurate value. I also understand that alcohol throws them off so they are generally not used to measure fermentation progress, use the hydrometer for that. That's all I can think of but I'm sure others here know more. FWIW, if you can grab one cheap it's a good tool to have if for nothing else then verifying your hydrometer measurements. Good luck! smileytoast.gif
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#3 The Chemist

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Posted 23 February 2007 - 08:19 AM

The refractometer measures the amount by which light is bent as it passes through a liquid. The more sugar in the solution, the more the light is bent. This is why you can use a refractometer to measure Brix.

It is true that alcohol does throw off the reading because as the alcohol content increases, you are now measuring refraction in a water/alcohol solution instead of just a water solution, which will have different refractive properties and thus give different readings.

Quoting a University professor I once knew: "Instruments are like biologists, you can't trust them: They just spit out numbers and don't know what they mean."

The refractometer has no way of knowing that you are using a water/alcohol solution instead of just plain old water.

You CAN however, correct for this effect. You can do a few fermentations where you check the sg with a hydrometer and the Brix with a refractometer and make a standard graph which will compare the readings to each other. You know have standard graph from which you can compare your refractometer readings to true sg readings in the future. Ie. no more hydrometer.

Hope that makes sense.
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#4 NorthernWiner

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Posted 23 February 2007 - 08:39 AM

QUOTE (The Chemist @ Feb 23 2007, 08:51 AM) <{POST_SNAPBACK}>
You can do a few fermentations where you check the sg with a hygrometer

I hope you're not using a hygrometer for checking SG. That instrument might be more useful for checking the humidity in your winemaking area. huh.gif

On the other hand, a hydrometer will measure SG.

Steve smileytoast.gif

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#5 Bill Frazier

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Posted 23 February 2007 - 08:56 AM

"Does anybody use a refractometer when checking their Brix? I am thinking about buying one. Is it more accurate than a hydrometer? Are there any disadvantages when using a refractometer?"

Russ-I don't believe there are disadvantages in using a refractometer for home winemaking. There are advantages such as small sample size, testing speed, ease of clean-up, etc. I also make beer. Some years ago I compared the use of the refractometer to hydrometers for measuring the specific gravity of wort at various times during the sparge (ie. while draining malt syrup, after the mash, into the kettle before boiling with hops. This can take about an hour). I believe these data show tgood comparison between the two methods of measuring "sugar". Here's the data;

RI (refractometer)
NRH (narrow range hydrometer)

zero minutes~RI 1.096, NRH 1.093
13 minutes~RI 1.096, NRH 1.093
22 minutes~RI 1.065, NRH 1.063
32 minutes~RI 1.037, NRH 1.037
42 minutes~RI 1.017, NRH 1.017
52 minutes~RI 1.009, NRH 1.008
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#6 MartyYule

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Posted 23 February 2007 - 09:02 AM

QUOTE (hz3gzy @ Feb 23 2007, 07:27 AM) <{POST_SNAPBACK}>
Does anybody use a refractometer when checking their Brix? I am thinking about buying one. Is it more accurate than a hydrometer? Are there any disadvantages when using a refractometer? I would appreciate some feedback.

Thanks Russ

From experience my refractometer always reads a point or 2 lower Brix than the hydrometer in fresh crushed must. Both have been calibrated but I go by the Hydrometer. I have also checked this with other refractometers and ithis difference seems to be pretty consistant

#7 Doyle

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Posted 23 February 2007 - 10:15 AM

I have both but use the refractometer the most. Both have their own set of advantages and problems. The refractometer is the easiest to use when measuring field samples or when checking your freshly crushed Must. A measurement takes less than a minute to make and record. The Hydrometer requires a larger sample and a bit more care in reading the number. During fermentation, I find it easiest to again use the refractometer to monitor the ferementation. Again less than a minute to get a reading but you have to correct that reading for the presence of alcohol and for the temperature of the must. You also have to have the starting must readings. In my case, I have a computer in the garage where I do the fermentation and the Refractometer spreadsheet is open. I enter the temp and brix reading and immediately get a corrected reading entered into the log. It is very easy for me. I also then have a dated log with all of the must temps, brix and SG readings by varietal. Here is a link to the spreadsheet as well as an explanation.
http://valleyvintner...fract_Hydro.htm
A hydrometer can be an accurate instrument but care must be taken to read the meniscus properly, make sure the float is not touching the wall of the sample tube and to make sure there is not a lot of particulate or gas in your sample that will cause errors. When working with red must I will take the refractometer over the hydrometer because of its ease of use.

..Doyle

#8 The Chemist

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Posted 23 February 2007 - 11:34 AM

QUOTE (NorthernWiner @ Feb 23 2007, 10:11 AM) <{POST_SNAPBACK}>
I hope you're not using a hygrometer for checking SG. That instrument might be more useful for checking the humidity in your winemaking area. huh.gif

On the other hand, a hydrometer will measure SG.

Steve smileytoast.gif


Haha! Opps! I had a brain fart.
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#9 WineyDog

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Posted 23 February 2007 - 12:41 PM

QUOTE (The Chemist @ Feb 23 2007, 12:06 PM) <{POST_SNAPBACK}>
Haha! Opps! I had a brain fart.
I wonder if that would be measurable with hygrometer.

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#10 NorthernWiner

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Posted 23 February 2007 - 01:24 PM

QUOTE (WineyDog @ Feb 23 2007, 01:13 PM) <{POST_SNAPBACK}>
I wonder if that would be measurable with hygrometer.

Only if it were a "wet" one.

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#11 Old Duffer

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Posted 24 February 2007 - 07:03 PM

QUOTE (hz3gzy @ Feb 23 2007, 04:27 AM) <{POST_SNAPBACK}>
Does anybody use a refractometer when checking their Brix? I am thinking about buying one. Is it more accurate than a hydrometer? Are there any disadvantages when using a refractometer? I would appreciate some feedback.

Thanks Russ


Russ,

Doyle is right on that the refractometer is fast and easy and referring Valleyvintner's website.
One of the owners, Mike Horton, is a member of my local club and they sell some very
good quality refractometers. Buy the highest quality that you can afford.

Rex

#12 The Chemist

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Posted 25 February 2007 - 08:31 AM

If you do go for a cheap one, be sure to 'calibrate' it yourself. That is, run a few fermentations while checking sg with a hydrometer and brix with a refractometer. Also, take multiple readings, 3 at the least, and average them. This way your cheap refractometer should give you dependable readings. Ie. don't use a pre-made chart that was made with a different, superior, refractometer.
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#13 Old Duffer

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Posted 25 February 2007 - 04:24 PM

QUOTE (The Chemist @ Feb 25 2007, 07:03 AM) <{POST_SNAPBACK}>
If you do go for a cheap one, be sure to 'calibrate' it yourself. That is, run a few fermentations while checking sg with a hydrometer and brix with a refractometer. Also, take multiple readings, 3 at the least, and average them. This way your cheap refractometer should give you dependable readings. Ie. don't use a pre-made chart that was made with a different, superior, refractometer.


Russ,

Stay away from cheap analytical instruments. ALL analytical equipment has to be calibrated
and they should be checked every time that you use them. So that means you have two types
of control samples. (1) The primary calibration standard and (2) a known check sample that
is in the range of your sample. While this is necessary when using the refractometer or any other
type of analytical instrumentation, a one time only check on the hydrometer should verify its
accuracy.

Rex
Retired Analytical Chemist




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