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Sorry...another hydrometer question

My hydrometer appears to be .002 measures off. I have never dropped it, but I have also never checked it for calibration until last light. I got the water temp down to 60 degrees and used a scientific thermometer to check the temp. It’s reading 1.002 in water. I kept dropping the temp down but still got the same reading. Dumped that water and poured in water straight from the faucet that was high 70s-80s. Still got the exact same reading. My assumption was that the temp would change the reading, and since it didn’t, I wonder how accurate my hydrometer is. Any suggestions? I now know to try distilled water and can try tapping the paper inside down, but does anyone have any other ways to check it before I buy a new one?

A difference of 1 or 2 points can be hard to read sometimes. You’re correct the value should have changed with temperature, but there’s no way an improperly calibrated hydrometer could cause temperature to not have an effect. Temperature matters because the density of liquids physically changes with temperature. Something else must be up.

Is the jar large enough for the hydrometer to float freely? It doesn’t have an obvious leak or anything like that? Is the water straight out of your faucet highly aerated maybe (because of the faucet screen)?

Check it with cool distilled water, and make sure its floating correctly. If you’re still off, you can probably just subtract 2 points from future measurements. Even if the scale is a little off, the basic principal of the hydrometer is going to work.

Oh yeah and too cold doesn’t matter as much as too hot. Water anywhere from 32 to 53 degrees is only off by one point, and 54-65 is no different from 60.

[quote=“Nate42”]A difference of 1 or 2 points can be hard to read sometimes. You’re correct the value should have changed with temperature, but there’s no way an improperly calibrated hydrometer could cause temperature to not have an effect. Temperature matters because the density of liquids physically changes with temperature. Something else must be up.

Is the jar large enough for the hydrometer to float freely? It doesn’t have an obvious leak or anything like that? Is the water straight out of your faucet highly aerated maybe (because of the faucet screen)?

Check it with cool distilled water, and make sure its floating correctly. If you’re still off, you can probably just subtract 2 points from future measurements. Even if the scale is a little off, the basic principal of the hydrometer is going to work.[/quote]

Nate, it’s in a hydrometer tube, so that shouldn’t be the issue. Water aeration might be an issue, but I think i can only tell when I use distilled water to test. The water temp issue is what bothered me bc the water straight from the tap is high 70s, and so I guessed that would have made an impact.

When you say hydrometer tube, do you mean a test jar or the tube it came in? The tube it came in is really too narrow to use as a test jar, it can distort the results. Roughly speaking the test jar should be about twice the diameter as the hydrometer itself to make sure it floats freely.

A test jar. Sorry, I’ve been using quart jars a lot lately and when I read jar, I thought of a big glass container. It’s the tube that came with it to do tests in. I have read that you can use fingerna polish to weigh the hydrometer down to calibrate it, but if the water temp doesn’t impact the measurement, I’m guessing it won’t matter

I assure you that no matter how out of cal your hydrometer might be, it will vary with temperature. Anything that floats will float differently depending on the density of the water, and the density of water has a well known dependence on temperature. Either your water wasn’t enough hotter to make an easily observable difference, or some other outside factor kept you from making the measurement accurately.

Don’t get hung up on the temperature thing. Just take note of where it measures with pure 60deg water, and offset by that much from then on.

Subtract .002 from every reading you do. Simple.

[quote=“Nate42”]I assure you that no matter how out of cal your hydrometer might be, it will vary with temperature. Anything that floats will float differently depending on the density of the water, and the density of water has a well known dependence on temperature. Either your water wasn’t enough hotter to make an easily observable difference, or some other outside factor kept you from making the measurement accurately.

Don’t get hung up on the temperature thing. Just take note of where it measures with pure 60deg water, and offset by that much from then on.[/quote]

So you wouldn’t recommend getting a new one under those circumstances? The temp thing was what bothered me and was the reason I figured I’d post since it was almost 20 degrees different and still showing the same reading.

Thanks for the advice (and patience)

If it was me, Id probably replace it eventually, just cause. But in the meantime, I wouldn’t let it stop me from brewing. I’d also hold onto it as an emergency spare, cause hydrometers have a nasty habit of breaking when you drop them.

Seriously though, you can totally still use it, just subtract 2 points (or whatever you measure the offset to be with 60deg distilled water). RDWHAHB.

If you go ahead and buy a space or replacement now, this one will never break. In brewing, as in life, things only roll off the table and break when you do not have a spare handy.

My hyrdo was reading 0.096 in water. I added nail polish to get it to read 1.000. The difference in gravity at 20* is around .002 which I assume is one line on your hydro (it is on mine). I can see this being difficult to determine a difference. If you buy a new hydro, you’ll run into the same issues. I’ve owned 5 hydros and the only one that read correctly was the one I broke. Just take .002 from all of your readings to get an accurate gravity.

Thanks for the advice

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