Do you use thermometer "strips"?

[voyager 663rd]

I was gifted some sourdough starter jars that come with the band (hours/days of the week) as well as a 'thermometer" strip.

Being kind of doubtful, I added hot water to the jar and stuck that strip on the side.

No change that I could see. I've seen lots of them advertised on amz and they usually get 4* ratings.

Mine does nothing.

Does anyone here use them? Do they really work?

 

[homebeerbrewer]

I've used them for home brewing beer. Usually, they're for a limited temperature range, so hot water would most likely show no change. Same as too cold of water. Does it show the temp range?