Salt Test - 48 hours and counting??

Mar 2, 2004
47
0
#1
Hi all,

So I just got a digital thermometer/hygrometer and I was running it through the salt test.

I saw the humidity climb steadily over the first 15 hours until it hit about 69%. I thought, OK, so it's -6%.

But after 24 hours it was up to 70%. This morning it was 71% and now it's up to 72%...

So I'm pleased that it's looking to be more accurate than I'd orginally thought, but everything I read about salt tests say it shouldn't take longer than 15-20 hours, right?

Is this just a quirk of the hygrometer I have? Or maybe I did something wrong when I mixed the solution? I mixed it till it was like damp paste...

Anyway - just wondering if this had happened to anyone else before...

thanks!
 
Sep 27, 2003
8,798
0
Puerto Rico/NYC
#3
That's very interesting, since I usually recommend 18-24 hours, which is way more than some sets of instructions. The main issue is, did you use a DOUBLE bag? You should not conduct this test with only one bag. Plastic ziplock bags are not always perfectly airtight, and a double bagging will provide added insurance for an accurate test.
 
Nov 25, 2003
2,438
0
Paradise CA
#4
other factors can affect the test. you will get wrong readings if its in direct sunlight id bet.
 
Oct 23, 2003
746
0
#5
I have tried this test several times with various amounts of water. I think it is important to make sure that your salt is not over-saturated. It works best for me if there is some dry salt around the edges of the dampened salt. If the salt is fully saturated the excess water will evaporate and raise the RH. When double bagged my hygrometer stabilizes in a couple hours, although I leave it for 24. Never hurts to try it again.
 
Sep 27, 2003
8,798
0
Puerto Rico/NYC
#6
Thank you FreedomGuns. That's an excellent point, and an error that's famous for screwing up those hygrometer salt tests. Definitely don't oversaturate that salt. DAMP salt doesn't mean making it like the ocean. :mrgreen:
 
Mar 2, 2004
47
0
#7
Hi there,

Yes, I did actually double bag it. And it's been sitting in the closet so the temp has been constant and no direct sunlight hits it.

It may be the salt/water mixture. I didn't have it very wet, but definitely no dry spots around the edges.
 
Oct 23, 2003
746
0
#8
The less air in the bag, the faster it should stabilize. Make sure there is enough air to allow free airflow around hygrometer and between hygrometer and salt without allowing any salt to contact the hygrometer. Any reasonable room temperature should be fine, as the salt should give off the same RH over a range of temps. That's about all I can think of. Let us know the results if you retry the test.
 

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