Mason Jar Hack

Posted by Dean Coolman | Dec 11, 2019 | Grow Hacks | 6 |

Quick check humidity in your mason jar. Amazon sells cheap humidistats. Trace the outline on a mason jar lid and cut out with a dremel tool. If your hole is right, you won’t have to seal around the opening and it will be a tight fit.

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About The Author

Dean Coolman

Living in Edmond, OK growing the dream homegrown. Caregiver for a relative allows me a higher plant count and the opportunity to try some small time breeding. I just can’t get enough of the grow, so I installed a Growtronix controller and some cameras to keep an eye on things when I’m at work. I just love looking in remotely to see what the girls are up to. 4 - Fluence SpydrX Plus LED fixtures split between two rooms for a harvest about every two months. Total organic living soil with well water, Recharge, silica, and Grean Bicycles Ocean’s Bounty soil amendment. 10 gallon Radical bags and Marrone Bio Innovations 3 Cannabis products.

6 Comments

Dabby Haze on December 11, 2019 at 5:10 pm

I haven’t found many of these cheap gauges to be very accurate measuring humidity.
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JustCoolin on December 11, 2019 at 5:35 pm

Best thing to do is gather them all together next to a rh meter your confident in and see what they do after letting them stabilize. You can remove the worst ones and even write a correction value on them. Just gives you an idea what humidity is doing, raising/dropping/stabilizing. Might not be perfect but they can be helpful for sure.
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- MarkasCannabis on December 12, 2019 at 8:01 am
  
  Exactly. I order them 20 at a time and they are usually all within 2-3 points with most being right on point. They are more than accurate enough for monitoring stagnant air in a small jar.
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Lysergic_Acid_52 on December 12, 2019 at 9:34 am

Nice I remember seeing this on Reddit r/stonerengineering but they used the round ones.

How well does that rubber gasket seal the jar?

Link to round humidistat 4-pack $15
https://www.amazon.com/JEDEW-Hygrometer-Thermometer-Humidifiers-Dehumidifiers/dp/B07GR67G1M/ref=mp_s_a_1_12?keywords=humidistat%2Bmonitor&qid=1576168223&sprefix=humidis&sr=8-12&th=1&psc=1
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- Dean Coolman on December 12, 2019 at 11:49 am
  
  It seals well enough for a 1-2 month cure. Once the humidity is locked in at 53% I use a regular lid and only burp once a week.
  If your hole is not a tight fit, just seal with some silicone.
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Knowmebymyguacamole on December 20, 2019 at 2:10 am

I made 6 of these a few years back with the round hygrometers. I used a rubber gasket on the top side and hot glue on the bottom. One of the standard size hole saw drill bits is the perfect size for the job. Had actually considered throwing a few hundred together and selling them, but now that I’ve seen it on here, probably not. I believe all six of mine are still kicking after two plus years.

As some have stated they aren’t super accurate (advertised +/- 5% rh). What I generally do to “calibrate” these is throw a humidity pack in a jar, seal it, and note the difference between the reading and the advertised humidity of the pack on a small round piece of tape on the lid.

As someone else noted, they aren’t exactly air right, so I wouldn’t recommend for long term cure. With that being said, I love being able to monitor humidity levels during the first couple weeks in the jar.

One last note, I’ve found that the batteries often come unseated, causing it to look as if the unit has failed. In my experience, 9/10 simply removing the back cover and reseating the battery fires it right back up.
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