# Refractometer Calibration Fluid



## Les Evans (Aug 25, 2005)

Hi Mike,
Mann Lake sells replacement calibration fluid for around $9. Is this something that might work for you?
Mann Lake 

I'm not sure if/or what type of glycerol will work(you may want to look into it if you don't already know) for what you need but I have seen the stuff on Ebay for around $4-$5


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## Sundance (Sep 9, 2004)

Making your own should be fairly simple if you have an accurate scale, like an old triple beam. Use distilled water and sugar in an amount within your range (by weight). It all hinges on having a good scale.


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## Michael Bush (Aug 2, 2002)

>Use distilled water and sugar in an amount within your range (by weight). 

I thought of that, but sugar is so hydroscopic I wonder how you know how much moisture there is in the sugar?

Seems like, at the price they want, a bag of pharmaceutical glucose would be useful for calibration.


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## Sundance (Sep 9, 2004)

That should work, I think Pharm glucose is like 99% or so......

With sugar you could oven dry 100 grams at 220F before adding 100 grams of distilled to yeild a 50% solids liquid. Lot of screwing around to save $10 or $15 though.


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## Curtis (Jun 25, 2005)

Refractometers are widely used to measure the amount of dissolved substances in solutions containing mainly sucrose. The relationship between refractive index and the amount of dry substance content is well known for sucrose and is the basis of the BRIX scale, which is the measure of the number of grams of sucrose present per 100 grams of aqueous sugar solution. That is, 50 BRIX means 50 grams of solid per 100 grams of solution. This relationship holds for a large number of similar substances and so the BRIX scale is widely used in the food industry.


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## Jim Fischer (Jan 5, 2001)

I don't have any glycerol or pharmaceutical 
glucose lying around, but I just put some pure 
Glycerin (from the drugstore) on my calibrated
refractometer, and it read 62% sugar, which
is well off the "% water" scale provided on
my refactometer, but is not off the "% sugar"
scale.

Maybe a few others can repeat the experiemnt
with their equipment to confirm my reading.


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## Curtis (Jun 25, 2005)

Yes Jim is right I was calibrating for sugar content not water content..
Thanks for the correction.
Curtis

[ July 24, 2006, 02:20 PM: Message edited by: Curtis ]


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## BeekeepingIsGood (Aug 12, 2012)

> I just put some pure
> Glycerin (from the drugstore) on my calibrated
> refractometer, and it read 62% sugar,


I believe my refractometer is calibrated. I just used the last of my calibration fluid that came with my refractometer to calibrate it. However, I was getting a higher number than anticipated for my honey, so I started measuring other things to see if I could get another point of verification.

Glycerine from the drugstore came in at 23.2% moisture
Cold-Pressed, Unrefined Flax seed Oil came in at 21.6% moisture - according to the internet this should theoretically be around 19%
My honey was showing at 18.9% moisture.

This is a very dark fall honey, a large percentage is likely from Japanese knotweed. How much would that impact refractometer readings?


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## crofter (May 5, 2011)

There are quite a few posts on using virgin olive oil as a calibration fluid. I tried 3 or 4 different brands and they did seem consitent in readings so I used that method. It was very, very close to the setting of the refractometer as it came from the box from Mann Lake.


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## BeekeepingIsGood (Aug 12, 2012)

Thanks Crofter! My model only goes from 13-25%. I was hoping to find something a within or closer to that range. Maybe I will try olive oil and see if there is any use in trying to estimate how far off the scale it is.

edit: I did measure olive oil and it actually showed up as 24.6%. The confounding factor here might be that I usually purchase my olive oil by filling up my own bottle from a bulk container...so perhaps it's been subject to more air exposure than most olive oils.

I also tried sunflower oil and that was 24.2%.

Seems for every sample that is lower than expected based on internet searches, I find a different sample that is higher than expected.


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## crofter (May 5, 2011)

I think you can pick up a small bottle of glycerine at a pharmacy. That may not have as much variation as Virgin Olive Oil. I think bottled olive oil of a top brand would be more reliable than something dipped at a bulk food store. I reset mine (slightly, but cant remember which way) taking olive oil as being 71.5 and my honey then indicated from just over 17% to just over 18% moisture even though much of it was uncapped on the comb.


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## BeekeepingIsGood (Aug 12, 2012)

> I think you can pick up a small bottle of glycerine at a pharmacy.


I did. the 23% moisture reading I got seems dramatically different than the '62% sugar' reading reported by Jim Fisher above, and a few moisture percentage points different than one would expect based on the commonly cited 1.4730 refractive index for glycerine.


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## Bee Herder (Jan 26, 2014)

crofter said:


> There are quite a few posts on using virgin olive oil as a calibration fluid. I tried 3 or 4 different brands and they did seem consitent in readings so I used that method. It was very, very close to the setting of the refractometer as it came from the box from Mann Lake.


This one :thumbsup:

Set aside an amount to maintain as a reference.


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## BeekeepingIsGood (Aug 12, 2012)

It's interesting that both my readings for olive oil and glycerine are off of the expected reading by about 2% moisture.

It could be the calibration liquid that came with my refractor, which in now 1.5 years old is now off, but my readings for sunflower oil and flaxseed oil are off by 2.5 - 5 % moisture in the opposite direction of the olive and glycerine.

So, I'm the least confident about any of the oils being reliable, and more confident that my calibration liquid has gotten me close to the right place.


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## sjj (Jan 2, 2007)

crofter said:


> ... I think you can pick up a small bottle of glycerine at a pharmacy. That may not have as much variation. ...


At a pharmacy you can get a 70% glycerine. 
One should ask for "Glycerine 99,5% ph. ".


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## crofter (May 5, 2011)

I picked up a little bottle of pure glycerine at food store yesterday (so the label says.) it shows 73 on my refractometer and the virgin oliive oil I have says approximately 71.5 so I feel confidient enough for honey ripeness. Of course if either the glycerine was not pure or the olive oil was off to one end or the other of average then my calibration could be off. Supposedly the instrument self corrects for temperature. If you can fairly easily get the proper calibration fluid it would give more peace of mind. I have spent more buying make do liquids but it was entertaining!


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## BeekeepingIsGood (Aug 12, 2012)

The bottle i have say Glycerine 100% v/v. USP. As best as I can tell 'ph." is a european thing similar to USP so it'll probably be the best I can find here. At $4.50 for 100ml it doesn't seem like a horrible option if I can get a consistent reading out of it over time.

Frank, where do you get your calibration fluid from? I used the last drops of the bottle that came with my refractometer to calibrate before testing out all these liquids. The company that sold me the refractometer wants to charge me $50 +tax/shipping for another 1ml bottle. In the bee supply catalogue from Proplis etc. it says to call them regarding calibration liquid, hopefully they'll be more reasonable, but I'm still waiting to hear back from them.

Looking here, I'm seeing '1.470 - 1.475' refractive index for usp glycerine, which is actually close to my 23.2% moisture reading.


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## sjj (Jan 2, 2007)

Pure glycerine should give 25.5% on your 13-25% Water in Honey Scale.


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## crofter (May 5, 2011)

The brix is only a relative term to compare _the refractive index_ of another substance to that of a _glucose /water solution_. The other liquid or even a solid would not necessarily contain any water or sugar. If your refractometer gives a reading of 73 on pure glycerine the assumption is that it will be sufficiently accurate for practical purposes on the water content of honey. Solids content and other sugars besides glucose makes it less than a perfect figure at the best. The blue/white boundary is also a fuzzy line. I dont have experience with how high a water content you can have before getting into spoilage concerns.


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## sjj (Jan 2, 2007)

crofter said:


> ... The blue/white boundary is also a fuzzy line. ...


The refractive index varies with the wavelength of light.
The splitting of white light into its constituent colors of a rainbow makes the blue/white boundary fuzzy. 
Take a lamp with yellow LED's. They give ~590nm light. 
Nowadays, it is about 5$ investment.


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## BeekeepingIsGood (Aug 12, 2012)

I find the line is fuzzy if I haven't strained or if I haven't properly cleaned and dried the refractometer (so there are mixed substances). The lines I get from strained honey that has settled are very distinct. Here's an example from my first harvest with a refractometer. Incidently, I found a source matching your reading on the brix scale.



> Solids content and other sugars besides glucose makes it less than a perfect figure at the best.


Should one expect darker honeys like japanses knotweed be off in a certain direction? Is their higher mineral content significant enough to make any difference?



> Pure glycerine should give 25.5% on your 13-25% Water in Honey Scale.


This is based on a refractive index of 1.4729 at 20C correct? 

It's a little frustrating that so many refractive index references don't give temp. references. But I do find reference to glycerine at 20c having a refractive index of 1.47399


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## sjj (Jan 2, 2007)

I have found: 

http://hypertextbook.com/facts/2005/ShirleyDeng.shtml

http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_0032/0901b803800322b7.pdf


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## BeekeepingIsGood (Aug 12, 2012)

It's interesting that there is so many references for two different readings. I'm not seeing references to anything in the middle, just one or the other.

I'm still l'm running out of ideas as to why there would be this divide. aside from temperature, I'm also having a hard time finding sources that specify the assumed light frequency with a wavelength of 589 nanometers.

At any rate, it appears that I've bought the 1.47399 variety of glycerin


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## crofter (May 5, 2011)

My instructions say a bright daylight source and also a bunch of chinglish about temperature compensation then ends with saying not to worry because this instrument self compensates for temperature variation. I wonder are you trying to get higher accuracy than necessary? As long as the moisture content is not above 18.4% or so I think you are safe. Buy a container of supermarket honey and see what it reads. Someone on the forum suggested that it is likely near the top of allowable water content since they are selling it by the pound!  Not sure if that is good advice but I read it on the internet.


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## BeekeepingIsGood (Aug 12, 2012)

> I wonder are you trying to get higher accuracy than necessary?


No, I want a cheap, easy to purchase, reliable liquid that I can use for calibration. When I started testing all the liquids others said could be used, and I saw very different results, I started asking more questions.

Under 18.4% is not accurate enough for me. It's not accurate enough for you either if you want to sell honey beyond the farm gate and label it as Ontario #1.


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## crofter (May 5, 2011)

OK! now I know what you are casting about for. I would not bother with an Ebay source or something homespun. It will have to be something with a definititive RI. Have a look here, www.thermoscientific.com You may have to get an instrument that is not compensating for temp. as that would be taking something on faith as well. You will have to do the math. There seems to be a big jump from the 75$ units to ones around 350.$ I definitely am not considering anything more than casual farm sales so my instrumentation reflects similar accuracy needs.


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## BeekeepingIsGood (Aug 12, 2012)

Crofter, do you have a proper calibration liquid? You now also have a bottle of glycerine. Why don't we sample our glycerine again in a year or so and test how constant of a substance it is.

Once we know the true value of a given bottle of liquid, it seems to me we could rely on it if we know it's RI remains steady over a reasonable period of time.


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