Adhesive strip thermometer and ice bath

[SubjectB]

Here's a riddle for you.

My glass carboy has an adhesive strip thermometer on the outside. If I place said carboy in a soda bucket filled with ice water, which temperature is the strip thermometer indicating, that of the wort or the ice water?

 

[KPaul]

The adhesive thermometer is not precision equipment and is really only picking up the temperature of the glass wall. With such a gradient between the ice water and the wort inside, you're not going to get an accurate wort reading until the two reach equilibrium.

It's like with a bowl of soup. You eat from the outside when it's too hot because it cools off faster on the edges. The same with the carboy in the ice water.

 

[SubjectB]

Thanks for the tip on how to eat hot soup.

Anyone else care try to answer the question?

 

[WayFrae]

You don't want to submerge the adhesive thermometer. They tend to not work after they have been submerged in water. Just keep the strip above the water line and it will give you a fairly accurate reading of the temperature of the beer.

 

[SubjectB]

Ooops

Well, since water is thermal conductive, what if I ignore the sticker--since it's probably ruined--and just measure the temp of the water in the bucket instead? Of course, I would allow some time for the water and the fermenting wort to reach equilibrium.

 

[tmendick]

It should be relatively close, depending on how fully submerged in the ice bath your carboy is.
Next time, what I used to do was cover the fermometer with packing tape before submerging.

 

[OscarBrau]

Fermenting wort tends to heat up by a few degrees over the ambient temperature. Any time I've kept a fermenter in a water bath, during fermentation the wort is 2-4 degrees warmer than the water. They match once fermentation completes.

 

[SubjectB]

The carboy is covered by water almost up to the shoulder and near the same level as the wort inside.

So, what I'll do from now on is rely on the temp of the water bath and assume that the fermenting wort is 5 degrees warmer during the initial 72 hours (?). I live in Central California, so even in the months we call "winter" I still need to leave the carboy in a water bath. The only difference is I use less ice than in the summer.

 

[tmendick]

5 degrees seems like a huge jump. I use better bottles though so the barrier is thinner, which I think would transfer heat better so the temp would be closer.