My wife got me this beer making kit for my birthday. The first two brews failed horribly due to bad sanitation, but the third one, an American Pale Ale, turned out alright. The only thing I didn't like about it, was that it very heavy, not unlike certain Belgian, quadruple beer.

I'm not too sure what caused it, but my guess is the fact that we've had a few very hot days while it was fermenting. It's either that, I misunderstood this page completely.

Anyway, as you can see, the kit contains a 1 gallon glass fermenter and I would like to find a way to constantly measure the temperature of my wort as it's fermenting. How would I measure that inside that glass fermenter? What kind of temperature sensor should I use?

In the future, I want to hook up said sensor to a small computer (Raspberry Pi, Arduino, etc.) so I can perform actual temperature control based on the temperature, but I'm having a hard time finding a method that doesn't involve making holes in the fermenter and simply sticking the sensor in through that and just using epoxy to close the hole and making it air tight.

I guess my question is: what's the best method to accurately measure the temperature of the wort inside my 1 gallon glass fermenter? Are there any wireless, waterproof temperature sensors out there that I can simply sanitize and toss in the fermenter or is that too simplistic?

Thanks for your help!

3 Answers 3


The kind of thing you seem to be in need of is a BrewPi. Basically the Pi, temp sensors, relays for heater/fridge and software to hook it all together in a nice little package.

You would likely have to make an extra hole for a temp probe, but rather than using epoxy for the probe try to find a small rubber grommet, you can often find these in home brew stores for holding airlocks in the top of brew buckets.

  • I'm definitely interested in a BrewPi, but right now, I feel that it's out of my price range and a bit overkill for a 1 gallon fermenter. I like the temp probe + grommet approach, though, if only because I could stick some other thermometer through the grommet (and later replace it with something more fancy). I'm a bit worried about contamination, though. Could I just have any sanitized thermometer stuck in there for two weeks without contiminating the wort?
    – user849924
    Commented Jun 14, 2016 at 9:33
  • If you sanitize it as you would sanitize your fermenter then no reason why it would not be OK sat there for 2 weeks. A simple alcohol thermometer through the grommet would work fine. so long as the bulb was fully immersed into the wort.
    – Mr_road
    Commented Jun 15, 2016 at 13:11

I would just put a self-advesive style thermometer on the jug ($4.00). Then keep it in a cool dark place where it will hold 65-72°.

With just a 1 gallon volume and a lot of glass surface area heatsinking the wort it will be pretty accurate without having to be in the wort.

A brew Pi, or T1000 temp controller works if you have refridgeration for it to control. Otherwise it's just a thermometer.

If you want digital thermo monitoring, a PC fan controler work good and have flat temp sensors you can tape to the outside of the fermentor or put in a thermowell. Easy DIY, put in a box with a basic 12v power supply, most can monitor 4 temp locations.


Warming up your fermenter is easy. Keeping it cool is a lot harder.

My best advice during the summer months is to brew something heat-tolerant during summer (NOT a lager) and find a cool place to keep it. You can easily control the temperature with a simple heat wrap and a cheap temperature controller. I like to tape the thermometer to the outside of the fermenter and cover it with a bit of paper tower for insulation: that way the thermometer is reading the jar temperature instead of the air temperature. Tape the heatwrap to the fermenter (but not over the thermometer) and plug it into the "Heat" outlet of your controller.

If you are lucky enough to own a refrigerator or freezer large enough to hold your fermenter then you can brew anything you want any time you want. Just turn the fridge's thermometer all the way down and plug the power cord into the "Cool" side of the controller.

There are improvements you can make to this setup like using an immersed thermometer, or fermenters with glycol jackets that are dynamically heated/cooled. But a temp controller, low-density heat wrap and a fridge are a great combination.

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