Hydrometers Giving Different Readings in the Same Water

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The Gulper
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For several years I've been using a Stevenson Reeves Hydrometer being totally happy with it.
Since having a second Just-In-Case-Hydrometer is a must for a homebrewer and my second Hydrometer (a German one, Balling scale) had been accidentally shattered without even much use I bought another Stevenson Reeves, triple scale (SG/Balling/Potential Alc.).
Then, comparing both in the same bucket of water I was surprised as my old Hydrometer read 0.998 while the new one 1.004. Quite a difference, I should say. Not so happy to see such a respected brand producing measuring equipment that differentiates so wildly.
Which one is correct then?

To calibrate my glass and electronic Thermometers, I use a Medical Thermometer as a reference point, making a simultaneous measuring of 40C water and marking the difference (like "+1C", "-2С", "EXACT") right on the Thermometers.

I wonder, what to use for a reference point when calibrating Hydrometers?
 

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You have to Google the amount of sugar per amount of water to get a specific gravity at a specific temperature. This way you can weigh the two ingredients and be sure that the resulting liquid has the gravity X. Then check which hydrometer gets of correct.

Is check with at least two coagulated gravity solutions, a strong one and a weak one.
 

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My memory says that brix is the percentage sugar in water.
10 brix = 10% sugar which is around 1040 (can't remember the exact conversion)
So plain water & 10 brix should give you a good indication.

My 2 hydrometers are 2 points apart. I need to mark them so I take the same one for all measurements of a brew
 

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well if your hydrometers are not reading 1.000 in water then I would get a new one. Mine always read exactly correct in water as they should since water is the reference point density for hydrometers.

I would contact the manufacturer and let them know about the issue because that seems rather odd.

One other thing to check, was the water at the reference temperature of your hydrometer? Usually that's 68F

One scenario that i can envision is that the water was colder than 68F so your new hydrometer was reading accurately but high because of temperature and your old hydrometer is not sealed properly and has taken on a tiny amount of water over time so was reading low.

I've gotten a bad glass blow on a hydrometer before and it leaked over time.
 

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Just check them both in distilled water. Whatever the difference is, just factor that in when you brew. It has to be distilled though, anything else could have varying gravities that will throw you off. It doesn't really matter if your hydrometers are off, so long as you have a reference for adjustment.
 
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Yes, I think I need to make one more control reading: this time in distilled water at exactly 20C, where both Hydrometers have been factory-calibrated.
If they are both off again, I'll have to mark it on each one how much exactly, just like I do on my thermometers. Then I'll have to make correction every time I use them. Damn.
Buying new hydrometers one after another until I happen to strike a perfect one isn't an option unfortunately.
 

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A consideration is that while I'd say "most" hydrometers have you read the bottom of the meniscus, I have seen that there are some that have you read the sides up against the vial you are using. They might not be off as far as you think? That said I still prefer reading the bottom and would consider a note regarding a correction for them.

Bummer. I totally understand having equipment that, though it can do the job, isn't working properly.
 
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I test them in a large bucket, both not touching sides and floating freely.
The meniscus thing, I'm aware of it: that was the difference between my old German Hydrometer (it was clearly stated in the manual to read from the upper edge of the meniscus) and my newer two British ones (the manual advises to disregard the meniscus distortion and to take the reading level with the liquid surface in the vial).
 

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I've never had hydrometers disagree by as much as you are claiming. Are you certain there wasn't a few bubbles clinging to the one you said was 1.004?

Usually hydrometers are calibrated at either be 60°F or 68°F and that won't make much difference for the comparison but maybe a single point.

If the scales and ranges of the two are greatly different and your eyes are getting less trustworthy as mine are, then that can be a possible consideration.

Regardless of why, I might just buy a third for a tie breaker and then toss the one that gives a reading furthest from the other two.

And I might also use a graduated cylinder or hydrometer flask instead of just floating them in a large bucket.
 
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The range is just slightly different: 0.970 to 1.150 on the single-scale and 0.990 to 1.170 on the triple-scale one.
Also, after a thorough inspection I see they're factory-calibrated at different temperatures: the first one at 68F and the second one at 70F. Even more confusion to add O_O

Nice idea to have two separate narrow-ranged hydrometers for measuring OG and FG! Another thing, there's nowhere to buy those here.
 
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You can recalibrate the one that's reading high just by filing off a little bit of glass from the bottom. Make sure they're both very clean that there's nothing stuck to it. You can also do a two-point calculation using a known concentration sugar solution. If they read the same difference from their respective 0 point )still differ by .004) recalibration should work. And by all means spin them and take another reading.
 

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Every homebrew quality hydrometer I've seen the paper scale is just rolled up inside. If it's just slighty off zero in distilled water you can VERY GENTLY tap the appropriate end and the paper scale will move. If it's way off , get a hew one.
 
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I don't think the paper scale is movable. What I see is that it's glued to the glass from inside with a tiny droplet of transparent glue.
Which makes a lot of sence, of course. Otherwise the hydrometer would change its reading wildly, depending on every shake.
 

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Just piling on the necrothread here, but I have had several hydrometers and the paper scale is never perfectly set to zero except the expanded scale (1.040 max instead of 1.100). With all of them, adjusting if their zero point was hi/lo, they would measure identically in prepared 1.040 and 1.060 corn sugar solutions.
 

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Just piling on the necrothread here,


2 months is necro now?

honestly, reading the first post again...was the older hydro heavier from more use? maybe give it a PBW soak... these things are measuring mg's here.....or grams what ever....

but if it has some slight more weight from being stuck in beer a lot could explain it....
 
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I suppose if I had a hydrometer as musty as to have a few grams of grease sticking to it from the hundreds of previous measurings 🐖, I'd take it with pincers and throw it into the dustbin however correct readings it was giving 💩

😂
 

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I suppose if I had a hydrometer as musty as to have a few grams of grease sticking to it from the hundreds of previous measurings 🐖, I'd take it with pincers and throw it into the dustbin however correct readings it was giving 💩

😂


in this case it'd be dried out sugar......
 

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just rinsed and clean after the soak, hydro is a total 1.000....i guess i should have weighed it on my cheap mg scale too, to see how much the PBW soak got off.....
Interesting that cleaning it changed the reading by two gravity points. Before cleaning, how did it look?
Edit: Are you sure it's not just a random reading difference? The change is in the wrong direction for the hydrometer being heavier.
Another edit: Disregard previous edit.
 
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Well, both hydrometers were perfectly clear at the time of the test.
No dried-out sugar or shyt on my brewing equipment (at least on my brewing equipment; can't state the same regarding the rest of my belongings).
 

bracconiere

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Interesting that cleaning it changed the reading by two gravity points. Before cleaning, how did it look?


honestly, it looked spotless, now i think otherwise....i wish i could try to duplicate the result, but my other hydro is pretty much brand new, this is the one i was using since 2006...
 

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I've never had hydrometers disagree by as much as you are claiming. Are you certain there wasn't a few bubbles clinging to the one you said was 1.004?

Usually hydrometers are calibrated at either be 60°F or 68°F and that won't make much difference for the comparison but maybe a single point.

If the scales and ranges of the two are greatly different and your eyes are getting less trustworthy as mine are, then that can be a possible consideration.

Regardless of why, I might just buy a third for a tie breaker and then toss the one that gives a reading furthest from the other two.

And I might also use a graduated cylinder or hydrometer flask instead of just floating them in a large bucket.
I worked in medical electronics for years. I came to the conclusion that you never carry 2 meters. They may or may not agree and then you are stuck. Use one, consider it done. This also applies to tape measures. Use the same instrument for each project.
 

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Come on guys this is HBT how has nobody encouraged the OP to ditch the hydrometers all together and buy an expensive easydens!
You wallet will then also read slightly less because it will get lighter too.
 
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Well, I'm a self-confessed retro-brewer: retro-styles, retro-techniques, retro-grade views on the wild fads of the modern homebrewing culture etc.
An Easyden could be a funny toy to have but you see, it isn't a retro-device, so it won't fit the rest of my retro-equipment, so no, thanks :)
 
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