Can hydrometer be left in primary?

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Senior Member
Sep 1, 2008
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Is there any reason not to just leave the hydrometer bobbing in a primary bucket like the floating thermometer. It sounds like a no-brainer that it would be easier than sanitizing and using a wine thief and test jar and all, but I don't think I've heard of people doing it.
Lots of people leave their hydrometer in the primary. Of course, if you have more than one primary you would need more than one hydrometer. Also, you may need a second hydrometer to measure the sg of wines in carboy.

There are two issues with leaving the hydrometer in the primary. You may not be able to read it accurately. However, for most of us, it will be close enough.

The other possible problem is that hydrometers are notoriously breakable. So if you need to stir the must/wine you may probably should remove the hydrometer first.

I guess it all depends on how accurate a reading you are comfortable with.

Even using a test jar pressed to the end of my nose, I still have to do a lot of squinting to come up with a reading.

Not to mention a bucket fermenter, I've never tried to take a reading through the class/plastic wall of a carboy because I know that it will be even more difficult than using a test jar.

With a bucket fermenter, I imagine that I'd have to stick my head down into the must to get an accurate, eye level, reading, but I would still wouldn't have much confidence with such a reading, because I would have to be reading it upside down!

If I'm going to be working with ballpark readings, I'll just throw the hydrometer away and really ballpark everything.

Besides, taste testing the sample is an important test, me, anyway!


i was thinking is it possable in wine making to use a portable refractometer to
measure your sg as thes are like 0000.00001% correct i use one to measure the sg in my marine fish tank.
Thanks, everyone. I think I'll just get a spare, then feel free to leave one in there. Seems like it would let me skip some sanitizing hassle. I don't feel like my readings need to be that fine, just confirming a kit wine is ready to move to secondary, ready for potassium sorbate, finings, that kind of thing.
Jay, you can use a portable refractometer to measure brix or specific gravity of the must but only before primary fermentation. Once fermentation begins and the sugar begins its conversion to alcohol a refractometer will not give you an accurate or even close measurement.

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