Just Curious

fsa46 · Mar 28, 2020

Just curious, how many of you have ever checked how accurate your hydrometer is ? I never gave it any thought until I looked into it after dropping mine and having to get a new one today.

After watching a couple YouTube videos I decided to test mine. I put it in some 60* demineralized water and it read 1.004. Not horrific but enough that I'll make the calculation when using it from now on.

Using 60* demin water it should read 1.000.

CDrew · Mar 28, 2020

If you have the usual tri-scale hydrometer, they are not that accurate. Good enough, but not perfect. But the range is too broad and the gradations too small for real accuracy. Just reading them precisely is a chore.

If you get a smaller scale hydrometer, like +5, -5 brix, you'll find the measurement accuracy is much better. Better hydrometers cost more though, so be aware and take care of them!

So I use a normal wide scale hydrometer at the start of fermentation (because the exact starting gravity is not that important) , and a +5, -5 one as it's finishing to get a better end point and to be sure that I'm not stuck near zero. It will cost more but it gives better accuracy so your call. I was a chemist way back when, and I just gotta know.

And to step back from the edge, wine was made for a looooonnngggg time before hydrometers were invented. So if you're off by 0.4%, you're likely ok. Just sayin'. And frankly, I'm surprised you're only off by 0.4%. I would have expected good to be plus or minus 1%.

cmason1957 · Mar 28, 2020

Also a single point check really isn't good enough to know how far it is off. You need to do one at the low end (1.000) and one at the higher end. By mixing up a known sg amount.

fsa46 · Mar 29, 2020

cmason1957 said:
Also a single point check really isn't good enough to know how far it is off. You need to do one at the low end (1.000) and one at the higher end. By mixing up a known sg amount.

You're absolutely correct.

The video I watched said to make a SG 1.06 sucrose solution using 30.1 g of table sugar and 173.9 g of distilled water.

Boatboy24 · Mar 29, 2020

Good news is your ABV is calculated with the difference between your beginning SG and your ending SG. If your hydrometer is off by .004 at the start, it should still be at the finish and your ABV will be the same. The difference will be in knowing whether your wine is done fermenting. But you should be able to tell.

fsa46 · Mar 29, 2020

Boatboy24 said:
Good news is your ABV is calculated with the difference between your beginning SG and your ending SG. If your hydrometer is off by .004 at the start, it should still be at the finish and your ABV will be the same. The difference will be in knowing whether your wine is done fermenting. But you should be able to tell.

Good point Jim. Just good to know how accurate an instrument is coming from China. lol

bstnh1 · Mar 29, 2020

I have a half dozen or so and having checked them all in 60 distilled water, every one of them is off by .002 to .004. I correct readings in my notes for the errors and for temperature, but in the end it really doesn't affect anything.

NorCal · Apr 1, 2020

I have a precision set of 4 hydrometers, as well as the $5 one. I use the precision one to get the initial reading, then the +5 to -5 brix to get the end reading. I use the $5 most the other times. Like others said, you really just want to see that it’s moving and the exact number itself isn’t all that important.

garymc · Apr 4, 2020

WOW! So, when I read .992 for 2 or 3 days, it could be .988 or .996 in reality. Jeez O Pete! That's huge! You know what that means? It means I should be writing some other number down! I'm surprised I haven't gotten alcohol poisoning or something.