Stick On Thermometer Accuracy

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I hope this isn't a foolish question or hasn't already been covered countless times, but I have one of those digital stick on thermometers, and my fermenter has been in the fridge at 19 degrees for 15 hours and the stick on thermometer still reads 26 degrees. I'm aware the plastic is an insulator, but is the accuracy of the thermometer potentially flawed, or is it that there hasn't been adequate time for the temperature to equalise between the bucket and the liquid? Do I need to be worried?
What temp was the wort in the plastic when you placed it into the fridge? If it was within 19 or so then I wouldn't stress. It should be fine, I'd say your stick on thermometer is a incorrect.
You could always pour off some wort and measure it with another thermometer if your stressing about it.
Well, despite chilling with ice, I could still only get it down to 26 before I had to move my supplies from the kitchen (shared house), I knew it was slightly too high for pitching but was wanting to get the yeast into the wort and started, since the strain I used could survive up to 40 deg. I had thought the temp would drop in the fridge and wasn't aware the plastic was such a good insulator.
Those stick on thermometers are crap. Forget using it and stick a decent probe one to the side of the fermenter. Before you know it you will be posting why is my yeast inactive = ie your beer will be at 4 degrees...

My fermenting fridge can drop 2 fermentors over 1degree per hour.

Also get a small fan (pc fan) in there to get the air moving, it makes a good difference.

Yup, it may be time to invest in a proper thermometer. The brew is fermenting well, i'd just rather it be fermenting at lower temps... I checked again and it seemeds to have dropped 2 degrees. Most likely the reading is out of whack anyway. Cheers for the feedback.
from my experience with them and i have heaps of them with fishtanks and fermenters. they usually arent terribly accurate. but i havent seem one more than 2 degrees out.
Been covered before and they are reasonably accurate. You may have a bad one. Always best to check thermometers for accuracy once in a while.
My stick-on normally matches pretty closely what stc-1000 is reading taped to side of fermenter.
^^^ I figured it'd been inevitably covered, but it's a cornucopia of information on here and it's a little bewildering trawling through it all.

Anyway, I have all this sorted now. After decreasing temp in the brewfridge down to around 14 -15 degrees, and also compensating for heat generated by fermentation, i've got the wort at a perfect 18 degrees! \m/ The air lock has slowed right down but is still steady. Possibly I got the overall temp down a tad too late in the process, it certainly wont be a fantastic beer as it had fermented for some time at 26 degrees, but fingers crossed it's not loaded with unwanted flavours and nastiness. I'm sure it will at least tastier than the last few batches given I attempted steeping grains and used all quality ingredients. Gradually eliminating all my weakest links with this brewing business and i'm determined to at least knock out ONE reasonable partial extract batch to show off with some light-hearted rivalry to a friend and fellow amateur brewer :D

I think in the future, I could be on the lookout for materials to make a basic wort chiller, to get those pitching temps spot on in the first place hence averting potential temp problems.
Hi might for future brewer strap your fridge control probe to the fermenter with so foam foam for insulation , that's how lots of it

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