refractometers

[reefman]

Does anyone use a refractometer, and are they specific to the process your are doing?
I have a refractometer for measuring salt water SpG, can it be used to measure wine as well, or do I need to purchase another?

 

[BernardSmith]

I am no expert but I would guess that a refractometer is a refractometer. It works on the principle that light is bent (refracted) by water in a very consistent and measurable way and that if you add anything to the water (sugar OR salt , for example) then the light will be bent at a different angle. That said, what is the scale your refractometer uses? Presumably the scale of a salinity refractometer is designed to provide the measure of salt in parts per thousand but if it does this by using specific gravity (SG) then SG is SG and the refractometer will have been calibrated to present the angle of refraction as gravity points - in which case a reading of say, 1.050 will be 1.050 whether the substance dissolved in the water is sugar or salt... If , however, refractometers that are used to measure the salinity of water use a different scale than specific gravity then disregard my comment. (I am assuming, however, that SpG is specific gravity (SG)
But that said, a refractometer poses a small problem and that is that once you have started the fermentation you now have alcohol being produced and the refractive index (RI) of alcohol is different than the RI of water. Moreover, as the fermentation continues the ratio of alcohol to water in the solution changes - so simply taking a reading will not provide you with an accurate measure of gravity of your wine- unlike when you use an hydrometer. - With an hydrometer you are not using the angle of refraction (the refractive index) to measure the specific gravity (density) of the liquid. With an hydrometer you are in fact measuring the density or gravity of the wine itself and the gravity DOES provide you with a good enough measure of the sugar content of the wine and if you know the starting gravity then also the alcohol content of the wine at any point in the fermentation process. In other words, a reading of 1.010 , for example, tells you that you have 4 oz of unfermented sugar in every gallon at this point but you only know that your wine is, for example, 10.5% ABV if you know that the starting gravity was 1.080, If the starting gravity was 1.050 then the ABV at this time is about 5.25%) ... BUT.. there are sites online that apparently provide "calculators" to enable you to convert readings from your refractometer even after the fermentation process has begun.

 

[reefman]

I thought the same thing and that they were only labeled differently, but I wanted other opinions to confirm.
Thanks.

 

[dralarms]

Reefman, if you measure plain water what does it read?

 

[reefman]

Tap or distilled?

just kidding.
I know it's 1.0, but the scale on the wine refractometer I looked at is in Brix.
The aquarium refractometer is in Sp G.
Does Brix translate to Sp G?

 

[reefman]

researching this a little further on the internet (it doesn't lie ) it's still confusing, but I'm guessing with a few different equations, I can convert an Sp G (which is what the refractometer measures) reading to Brix, Salinity, water content, alcohol content, etc.

 

[Bartman]

I have never needed a refractometer to make wine; your hydrometer should do the job 99.9% of the time. If I was growing grapes and needed to know the sugar level as they ripened, then, yes, a refractometer would be useful/necessary. Otherwise, why spend $100-$300 on an unnecessary tool? (unless you want a new toy)

 

[reefman]

They are almost as cheap as hydrometers now....$15- $20 on ebay, that's why I started this thread...I've been thinking about getting one.
You can still spend hundreds of dollars on them, but prices are dropping.

 

[sour_grapes]

Not so fast!

Bernard asserts that index of refraction only depends on density (SG). However, later in the post, he provides a counterexample to that assertion. As he cites, and many of us know, a refractometer gives "wrong" values for the SG after fermentation has started. Why? It is because the index of refraction for alcohol is different (for a given density) than that of a water/sugar solution.

The index of refraction of a material depends on many things. It does depend significantly on the density, so Bernard is on the right track. However, it also depends on the optical properties (such as polarizability) of the molecules, including the dissolved molecules. Thus, liquids having the same density, but different optical properties, will register the same density on a hydrometer but different densities on a refractometer.

I strongly suspect that dissolved sugar and dissolved salt will behave differently, as those molecules have very different polarizabilities.

You could always mix up a sugar solution and a salt solution to have the same SG (as measured on a hydrometer) and then compare!

 

[reefman]

Ok, I agree, and I take back measurement of Alcohol....I actually did read that on one of the websites I was researching.
I'll try to measure both salt water and sugar water this weekend and post my results.
From my readings on wikipedia, it is used in many industries.

Quote:
"In veterinary medicine, a refractometer is used to measure the total plasma protein in a blood sample and urine specific gravity.
In drug diagnostics, a refractometer is used to measure the specific gravity of human urine.
In gemology/gemmology, the gemstone refractometer is one the fundamental pieces of equipment used in a gemological laboratory. Gemstones are transparent minerals and can therefore be examined using optical methods. Refractive index is a material constant, dependent on the chemical composition of a substance. The refractometer is used to help identify gem materials by measuring their refractive index, one of the principal properties used in determining the type of a gemstone. Due to the dependence of the refractive index on the wavelength of the light used (i.e. dispersion), the measurement is normally taken at the wavelength of the sodium line D-line (NaD) of ~589 nm. This is either filtered out from daylight or generated with a monochromatic light-emitting diode (LED). Certain stones such as rubies, sapphires, tourmalines and topaz are optically anisotropic. They demonstrate birefringence based on the polarisation plane of the light. The two different refractive indexes are classified using a polarisation filter. Gemstone refractometers are available both as classic optical instruments and as electronic measurement devices with a digital display.[1]

In marine aquarium keeping, a refractometer is used to measure the salinity and specific gravity of the water. In Automobile Industry keeping, a refractometer is used to measure the Coolant Concentration and Ph Value of the Coolant Oils for CNC Machining Process.

In homebrewing, a refractometer is used to measure the specific gravity before fermentation to determine the amount of fermentable sugars which will potentially be converted to alcohol.

In beekeeping, a refractometer is used to measure the amount of water in honey."

 

[BernardSmith]

Ok, I agree, and I take back measurement of Alcohol....I actually did read that on one of the websites I was researching.
I'll try to measure both salt water and sugar water this weekend and post my results.
From my readings on wikipedia, it is used in many industries.

Quote:

In marine aquarium keeping, a refractometer is used to measure the salinity and specific gravity of the water. In Automobile Industry keeping, a refractometer is used to measure the Coolant Concentration and Ph Value of the Coolant Oils for CNC Machining Process.

In homebrewing, a refractometer is used to measure the specific gravity before fermentation to determine the amount of fermentable sugars which will potentially be converted to alcohol.

In beekeeping, a refractometer is used to measure the amount of water in honey."

I think sour_grapes is right.
Gravity may be gravity but if the refractometer is calibrated to measure the refractive index of parts per thousand of salt dissolved in water it does so by measuring the distortion of the path that light takes as it travels through water with a quantity of salt dissolved in it compared to water with nothing dissolved in it, (that difference is the "angle" ) then the equivalent SG of such a sample of salt water will have a very specific and known specific gravity reading, let's call it 1.xyz. But a sample of water with sugar in it that produces the SAME angle of refraction may have a very different density - 1.xbc - so you would not be able to read off the scale assuming that the density it appears to show is accurate - What is accurate is the refractive index but if the RI for sugar and water are different then a refractometer calibrated for measuring the salinity of water won't tell you the sugar content of must.

 

[salcoco]

http://valleyvintner.com/cp-tips-links.html

go to this link and you can download a spreadsheet that allows use of a refractometer during fermentation. I have checked it and have used it for many years without fail.

 

[BernardSmith]

Reefman, I make lacto fermented pickles so I took the opportunity to test the refractometer using a brine solution for making sour pickled cucumbers. The brine was about 3.5% saline and the gravity, using my hydrometer, read 1.020. I took a sample and applied it to my refractometer and the gravity reading was 1.014. Could be that my refractometer needed recalibrating but I then made up a solution of sugar water so that its gravity was 1.020 and then applied a sample of that to the window on my refractometer. The refractometer confirmed the reading at 1.020.. so salt and sugar do NOT have the same refractive index, and so if your refractometer has been calibrated to provide PPT or % salinity then I think you may need to obtain a refractometer calibrated to map the refractive index of sugar dissolved in water to specific gravity...

 

[terrymck]

Wow! you guys don't have enough to do.

 

[BernardSmith]

Wow! you guys don't have enough to do.

Nah... bored out my gourd... (not!). ..

 

[reefman]

Reefman, I make lacto fermented pickles so I took the opportunity to test the refractometer using a brine solution for making sour pickled cucumbers. The brine was about 3.5% saline and the gravity, using my hydrometer, read 1.020. I took a sample and applied it to my refractometer and the gravity reading was 1.014. Could be that my refractometer needed recalibrating but I then made up a solution of sugar water so that its gravity was 1.020 and then applied a sample of that to the window on my refractometer. The refractometer confirmed the reading at 1.020.. so salt and sugar do NOT have the same refractive index, and so if your refractometer has been calibrated to provide PPT or % salinity then I think you may need to obtain a refractometer calibrated to map the refractive index of sugar dissolved in water to specific gravity...

Thanks BernardSmith!
I didn't have a chance to test it myself. At $20 and some change, I'll just buy one for my wine.

 

[olusteebus]

If I buy this little place, I might buy one. A good one.

http://vinesmart.com/wine/Real_Esta...Offering?_ga=1.39448355.1461918607.1446055984

 

[firstime]

I have also been thinking about picking up a refractometer from eBay. 1 good thing about it is if you use your test tube for the hydrometer the juice is sometimes thrown away. The refractometer uses only a few drops compared to ruffly 3-4 oz or so. Plus you can always use the conversion charts or download a app.

 

[Boatboy24]

http://www.amazon.com/dp/B003H7ILCW/?tag=skimlinks_replacement-20

 

[wineforfun]

1 good thing about it is if you use your test tube for the hydrometer the juice is sometimes thrown away.

Why is that? Am I missing something?
I fill my test tube up with wine, take reading, and dump back into primary/secondary.