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dralarms

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Just bought a new refractometer, made to measure alcohol, directions say will not read properly if it's a sweet wine.

So. I took a wine that's at .990, calibrated the unit using distilled water, and took my measurment. Well it says my wine is 25% how can that be? Since there's 10 points from .990 and 1.000 do I subtract 10 points from the reading?
 

BernardSmith

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Is this refractometer calibrated for alcohol or for water? Typically, a refractometer is calibrated to measure the angle at which light is bent through water as the solvent, but if the solvent is alcohol then you need to apply quite complex formulae to account for the different angle of refraction at which the light bends at different volumes of alcohol in the solution.
 

dralarms

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It's designed for alcohol.
 

dralarms

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Once the wine clearshop completely I'll add sugar to get to 1.000 and retest to see what happens.
 

salcoco

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there are a number of spreadsheets on the internet that convert refractometer numbers measuring alcohol. suggest using these spreadsheet to verify your readings against hydrometer.
 

dralarms

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there are a number of spreadsheets on the internet that convert refractometer numbers measuring alcohol. suggest using these spreadsheet to verify your readings against hydrometer.
It's not a regular refractometer. It's designed to measure alcohol
 

Arne

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Did the meter come with instructions? If so did the mfr. list a website? Shoot them an email, explain your results and see what they say. Arne.
 

dralarms

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Did the meter come with instructions? If so did the mfr. list a website? Shoot them an email, explain your results and see what they say. Arne.
Good idea. Thanks
 

sour_grapes

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I realize that you are assuming that 0.990 means that you don't have to worry about any residual solids (like sugar) messing up your measurement. Although that makes sense to me, these guys seem to say that's not good enough:

http://www.misco.com/Downloads/MISCO-TB-WINE.pdf

FINAL ALCOHOL CONTENT
Computing Alcohol by volume in finished wine.
Now that the wine is complete, you need to meas- ure the alcoholic strength or alcohol by volume. This is easily accomplished using one of two meth- ods:
1. Roesener Method based on specific gravity and refractive index.
2. Following the distillation method of the AOAC or OIV.

It is impossible to directly measure the ethanol content of wine using either a refractometer or hydrometer alone. That is because, by their nature, these two instruments are designed for measuring binary, or single component, solutions. The direct measurement by a single instrument is precluded since the combination of water, alcohol, and sugar in the wine represents disparate factors, each dif- ferently influencing the readings of these instruments.
They go on to describe how to perform both of those two methods. In the second one, you distill the solution to get rid of the residual solids, but then re-dilute back to the original strength, and then use a calibrated-for-alcohol refractometer such as yours.

Personally, I'd give the first method a try, although, ironically, it requires a calibrated-for-sugar refractometer!
 

dralarms

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I realize that you are assuming that 0.990 means that you don't have to worry about any residual solids (like sugar) messing up your measurement. Although that makes sense to me, these guys seem to say that's not good enough:

http://www.misco.com/Downloads/MISCO-TB-WINE.pdf



They go on to describe how to perform both of those two methods. In the second one, you distill the solution to get rid of the residual solids, but then re-dilute back to the original strength, and then use a calibrated-for-alcohol refractometer such as yours.

Personally, I'd give the first method a try, although, ironically, it requires a calibrated-for-sugar refractometer!

Thanks Paul,

I'll let it clear out and see what I get then,
 

balatonwine

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Not only will residual sugars cause inaccurate readings in an alcohol refractometer, so will pigments in the solution. Even white wines have pigments to some extent.

Sour_grapes gave a good link. Another, less accurate but even easier, estimator for alcohol content:

http://www.monashscientific.com.au/AlcoholDeterminationBySpecificGravity.htm

If one needs more accuracy, then one needs to start doing some bench work at the distiller. No way around it.
 

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