My stupid hydrometer and refractometer disagree with each other

[phug]

Okay I'm leaning towards it being a problem with the refractometer since it's a cheap one ordered off Amazon from Hong Kong.

They both read the same for water. And the refractometer is an atc model.


But I just took some side by side measurements of the same juices

Apple juice. Hydrometer reading 1.048 at 60 f
Refractometer 1.042 SG and 10.6 on the brix scale. It has both.

Pear juice. Hydrometer reading 1.056 hydrometer at 60f
Refractometer 1.051 and 12.5 brix

I am grumpy. It's not even a consistent percentage of variance

 

[doug293cz]

Okay I'm leaning towards it being a problem with the refractometer since it's a cheap one ordered off Amazon from Hong Kong.

They both read the same for water. And the refractometer is an atc model.


But I just took some side by side measurements if the same juices

Apple juice. Hydrometer reading 1.048 at 60 f
Refractometer 1.042 SG and 10.6 on the brick scale. It has both.

Pear juice. Hydrometer reading 1.056 hydrometer at 60f
Refractometer 1.051 and 12.5 brix

I am grumpy. It's not even a consistent percentage of variance

Have you confirmed (from the paper in the stem) that the hydro is calibrated for 60°F and not 68°F? Only other thought that I have is that maybe fructose behaves differently (either for an index of refraction or SG or both) than sucrose and maltose, but that's just a wild azz guess.

Brew on

 

[Hex23]

Only other thought that I have is that maybe fructose behaves differently (either for an index of refraction or SG or both) than sucrose and maltose, but that's just a wild azz guess.

Brew on

Not just a WAG. That's quite true. It's why we need "wort correction factors". Search for it here on HBT.

Edit: I guess it would be better to just say that index of refraction is not a measure of gravity, and so different sugar solutions at the same SG would have different IOF. Not sure why the readings are so different for fructose based juices. I thought that's what many refractometers are calibrated for. Maybe you have a refractometer that's supposed to be calibrated for beer wort ?!?

 

[stpug]

Have you checked them both with (preferably distilled) water? Determine where on the hydro you should be taking your reading from and accounting for any inaccuracies in the equipment?

 

[Oginme]

Your refractometer is set up for sucrose measurements. Fructose has a different refractive index and refractometer calibration. When reading the sugar content of wort using a refractometer, we typically record the readings in Brix and use a table to convert to specific gravity.

 

[PlinyTheMiddleAged]

Phug,

I'm pretty sure the cheap refractometers have a bad sg scale - the Brix might be right, but don't trust the sg scale.

If I convert your Brix values to sg (with a default wort correction factor of 4%), I get
10.6 Brix is 1.041 sg and
12.5 Brix is 1.048 sg
So, that's a delta of 7 and 8 points from your sg scale - kind of consistent.

Now, if I zero out the wort correction factor (since you are not working with wort, but with real fruit sugars)
10.6 Brix is 1.042 sg
12.5 Brix is 1.050 sg
That's a delta of 6 points for both of those - consistent.

But you still haven't figured out which one is right - you can mix up a known sample. Mix 10 grams of sugar with 90 grams of water and you have a solution of 10 Brix. See what your refractometer tells you. If it reads 10 Brix, you know you are good to go and you just need to ignore the sg scale.

 

[phug]

the one I got is http://www.amazon.ca/gp/product/B00JVIIGLW/?tag=skimlinks_replacement-20 which may have a wort correction factor fudged in.

I also double checked my hydrometer and it's calibrated for 60f, and is intended to be read at the lowest dip in the surface. because that did occur to me.

I did compare my brix values to the sg scale using brewers friend to cross check the results, and my brix and sg values matched, so it might actually have a good brix to sg scale. unless, of course the math there is no good

and yeah, I'm going to bust out my blade scale a mix up a 5 10 15 20 brix solution.

I'm assuming those would be

5g sugar 95g water
10g sugar 90g water
15g sugar 85g water
20g sugar 80g water. using distilled water.

my scale is accurate to 0.1 grams and has a calibration certificate, so that should be easy enough.

 

[phug]

the brix scale on this one seems to match up accurately to sg, at least close enough using sean terrill's website as well, after removing the wort correction factor

 

[PlinyTheMiddleAged]

...I'm going to bust out my blade scale a mix up a 5 10 15 20 brix solution.

I'm assuming those would be

5g sugar 95g water
10g sugar 90g water
15g sugar 85g water
20g sugar 80g water. using distilled water.

Yes, that's my understanding as well. I don't know how important the distilled water is, but it's not going to hurt to use it. I've got some of the crappiest water in America (SoCal drought water) and I get 0.0 Brix and 1.000 sg with refractometer and hydrometer respectively when I check it out.

I should mix up some standards to check out my refractometer...

 

[b-boy]

Do you know anyone else with a refractometer? You could do a side-by-side with them to determine if it's really your refractometer. If it's not you should get similar readings.

 

[phug]

Refractometer, no.

I suppose I could go down the street to get my FIL's hydrometer as a third reference point, but that probably won't do me any more good than mixing up some calibration solutions.

 

[phug]

Ok so I did some testing this weekend.

I measured out table sugar using my precision scale. It's calibrated and certified to be accurate to 0.1g

I then put that sugar into my cleaned dried Hydrometer test tube, and measured the sugar measurement container to make sure it read 0.0g

I then placed the tube and sugar on the scale and added distilled water and measured out the weight. Since Brix is the sucrose percentage of a solution by weight, it was easy to determine what the Brix Value should be, which I then plugged into brewer's friend to provide the correct SG value for that brix value.

I then capped my hand over the end of the tube, and shook it back and forth until all the sugar had dissolved. I then placed my rinsed and dried hydrometer in the solution, and used a pipette to get my sample for the refractometer and placed that on the window and let it sit to match the temp of the refractometer. Refractometer samples were done twice to ensure that the values matched. Readings were taken with daylight.

it would seem that my refractometer reads low by about 3%, and my hydrometer reads about 6% high. and of course if I compare them I get a difference of 9% which is a noticeable difference.

Both were calibrated with distilled water as you can see from the spreadsheet I put together.

I did throw out some of the variance values because they were just wierdly off, and I wanted to get a useful correction value that would be close to accurate across most of the range. Also, I can't rule out some kind of tester error on that.


Moral of the story. Just because your hydrometer or refractometer reads 0 at zero with distilled water, does not mean that it is accurate. Please test it using more than one known value. Also, I'm very disappointed in my hydrometer. It has been lying to me all along. This is very important when mixing and matching readings from different instruments. At least it's a percentage of difference that's reasonably consistent. So as the reading approaches 1.000, then the absolute error gets smaller and smaller. Apparently my beverages have been only about 94% of the alcohol percentage advertised.

The good news from all of this is that my Refractometer at least has an accurate SG and Brix scale, provided that I adjust for the fact that it's low by 3%.


****row 8 of the spreadsheet looks like it's garbage data most likely from an instrument reading perspective, and possibly also from a solution generation perspective

 

[stpug]

Most refractometers have a little adjustment knob/screw on top near the crystal to allow you to calibrate your instrument. This should at least alleviate your 3% difference the refract is measuring.

 

[phug]

Most refractometers have a little adjustment knob/screw on top near the crystal to allow you to calibrate your instrument. This should at least alleviate your 3% difference the refract is measuring.

Yup, found it and used it when I calibrated it at 1.000 with distilled water. I'll have to try adjusting it at a higher value to read correctly and then see if that carries over down the line and doesn't throw off the baseline distilled water reading. At least it's off by a consistent amount and I know how to compensate for it.

Finding time to mixup the necessary solutions with wife and kid around can be troublesome. Maybe I'll just take a given sample. Adjust to the corrected value and then check the zero reading with distilled water.

I'm still disappointed with my hydrometer. It's French, or so it tells me.

 

[nealm]

If the sugar solution is 10% by weight shouldn't you be adding 135g of water to 15g sugar. 15g in 150g is a 9.09%.

Nealm

 

[phug]

you're right it is, and if you take a quick look at my spreadsheet, the line that shows 15 g sugar and 150g water shows a calculated brix value of 9.09.

I realized that I had screwed up in terms of getting an exact reference point of 10 brix. but I also realized that it didn't matter WHAT the brix value of the sample was, as long as I knew exactly what the brix value was.

This was particularly helpful because I wouldn't have been able to float my hydrometer in all of the samples if they had been made using the same amount of water.

I've also decided I might not calibrate my refractometer again, since the scale on the viewpiece says Wort SG. And since my readings are 3% low, and most wort correction factors seem to multiply your reading by about 1.04 or thereabouts, I may just have myself a beer refractometer with a must correction factor of .9697

 

[fermentology]

Brix to SG is not linear so when using your refractometer don't use the SG side. As stated before refractometers are not set up to measure wort, but rather wine so they don't accurately correlate between brix and plato. In order to do that you will need to determine your corrective factor. Take measurements of wort with a hydrometer and your refractometer. Over time you will be able to calculate your corrective factor. Brewer's friend has a spreadsheet that you can download to do this. When you have your corrective factor it will help you convert brix to plato, which can then be converted to SG if need be.

Plato=Brix/(corrective factor)

Mine is 0.91 so my refractometer is pretty crappy

SG = Plato/ ( 258.6 - ( ( Plato/ 258.2 ) * 227.1 ) ) + 1

Hope this helps.

 

[phug]

Ok, everyone keeps saying that brix and SG are non linear, fine.

But if I can't trust the brix vs SG scale on my refractometer, then I can't trust my hydrometer either, And I can't trust the brix to SG calls I've found online.

When I look at the SG scale on my refractometer compared to the brix, I get the same values when I look at the corresponding marks on my hydrometer And I get the same SG value when I plug the brix reading into the online calculators I've found.

I know that the rule of four is not accurate, but I also know that my brix/ SG scale on my refractometer do not follow the rule of four.

So please explain. I know there are super crappy refractometer a out there, but surely there must be one where someone used the right conversion table when printing their scale.

 

[phug]

I'm not saying wort correction factors don't need to be used.

But most of my fermentations are ciders. so I shouldn't need a wort correction factor.
and when my refractomer reads 8.8 brix and the line intersects 1.035 I don't see why I can't trust the SG scale on it.

16.2 brix intersects with 1.066, 15.9 brix intersects with 1.065, and 30.70 brix intersects with 1.132.5ish on the scale on my refractometer. I don't where those conversions are wrong.

 

[fermentology]

I'm not saying wort correction factors don't need to be used.

But most of my fermentations are ciders. so I shouldn't need a wort correction factor.
and when my refractomer reads 8.8 brix and the line intersects 1.035 I don't see why I can't trust the SG scale on it.

16.2 brix intersects with 1.066, 15.9 brix intersects with 1.065, and 30.70 brix intersects with 1.132.5ish on the scale on my refractometer. I don't where those conversions are wrong.

For the sake of comparing refractometers I'll list where that corrected values for my refractometer with the brix values you listed

8.8 = 1.039
16.2 = 1.073
15.9 = 1.072
30.7 = 1.147

These are the values that I would get after calculation and using the corrective factor that I calculated.

The best thing for you to do is to take measurements with your refractometer and a hydrometer and compare them (assuming they are all calibrated properly). If they are different, continue to take measurements and notes to see if there is a correlation.

 

[stpug]

...most of my fermentations are ciders. so I shouldn't need a wort correction factor.

when my refractomer reads:
8.8 brix and the line intersects 1.035
16.2 brix intersects with 1.066
15.9 brix intersects with 1.065
30.7 brix intersects with 1.132

I agree with your statement above. When using simple sugar solutions (sugar, grapes, apples, etc) those values are what I'd expect.

They would not be accurate for reading wort, as you already know.

 

[phug]

For the sake of comparing refractometers I'll list where that corrected values for my refractometer with the brix values you listed

8.8 = 1.039
16.2 = 1.073
15.9 = 1.072
30.7 = 1.147

These are the values that I would get after calculation and using the corrective factor that I calculated.

The best thing for you to do is to take measurements with your refractometer and a hydrometer and compare them (assuming they are all calibrated properly). If they are different, continue to take measurements and notes to see if there is a correlation.

Does your refractometer have an SG scale as well? at the moment I'm interested in where the refractometers differ in their SG scales to Brix scales.

if I were using a correction factor, I would have to apply it to the Brix WRI, to get my actual brix, and then convert to get my SG. for that matter I could, from the looks of things look at my refractometer SG reading and get my SG WRI, for lack of a better term, and apply the same wort correction facotr, to obtain my refractometer SG.

so what I'm trying to say is that based on MY refractometer, and the scale that it has, I can trust the SG reading to the same extent that I can trust my Brix readings, as they will both be off by the same amount if I'm reading wort, and need to then use a wort correction factor to adjust.

 

[fermentology]

Does your refractometer have an SG scale as well? at the moment I'm interested in where the refractometers differ in their SG scales to Brix scales.

if I were using a correction factor, I would have to apply it to the Brix WRI, to get my actual brix, and then convert to get my SG. for that matter I could, from the looks of things look at my refractometer SG reading and get my SG WRI, for lack of a better term, and apply the same wort correction facotr, to obtain my refractometer SG.

so what I'm trying to say is that based on MY refractometer, and the scale that it has, I can trust the SG reading to the same extent that I can trust my Brix readings, as they will both be off by the same amount if I'm reading wort, and need to then use a wort correction factor to adjust.

I'll have to double check to see how my Brix correlate to SG on my refractometer. It does have both scales.

I will say that my refractometer looks like this.