Spakon 6 Pcs Heat Sensitive Sheet Temperature Sensitive Sheet 6 Color Changing Heat Board, 24 to 34 Celsius Degree Transition for Science Experiment (10 x 10 Inch)

Got these and was disappointed because they would not change color. I set them aside planning on returning them. The next time I picked them up, they worked, just as they should. I use them one electronic circuit boards to find the hot spots. Example: When something fails after running for a while, it's probably a heat problem. These sheets will find the location of the heat. The part under the sheet is either defective, needs a fan or heat sink. Often aheat snk will solve the problem.

Save your money. These will barely react for 1-2 days out of the packaging and then they become useless. I bought them to add to my sensory wall in my classroom, total disappointment.

Works great (on shiny side)!

Works fine at advertised temperature ranges however maximum temperatures are black again.

I like that they change color but dang it's a 6 inch by 6 inch sticker for almost 20$

Doesn’t work well, hands have to be very warm

This did not work. I only noticed color changes if I had the paper sandwiched between both my hands but that is not the use that was described. It worked nothing like the photos.

My child loved it.