Stick-on fermenter thermometers

[Ben Dean]

I have recently decided to control my fermentation temperature more accurately, so I am now putting my fermenter in a tub of water with an aquarium heater (during winter). The stick-on thermometer on my fermenter appears to read 4 deg C higher than my thermometer reading of the water. Does anyone know if those stick-on thermometers are made to account for the difference between ambient temperature and wort temperature, or are they just massively inaccurate?

Cheers

Ben

[Tom C]

Just massively inaccurate!

[Ben Dean]

Figured as much, cheers. Seems I've been fermenting quite a bit cooler than I thought.

[Jamie McQuillan]

 I wondered myself how accurate they are. It turns out the ones I use are spot on with my thermometer when I read the temp showing in green, not blue or black and when measuring the wort temp in the fermenter. I suspect that the water surrounding your fermenter can be colder than the wort, especially if the wort is actively fermenting. My brews will generally warm up above ambient (i.e they will be 20 deg at ambient 18 deg). 

[The Wine Brewer]

Hey I got a great video on how to read Stick on Thermometers here: https://www.youtube.com/watch?v=IBb2q2GI3pY