Tempilstik Temperature Indicators - te 750 tempilstik

It only works on metal that is already hot.

This product is junk. All it does is crumble. I heated a piece of brass that I’m annealing to red hot and it wouldn’t even smoke. Don’t waste your money. Whoever screwed the pen together must have loctited it as it won’t unscrew. Just pushed it through from the bottom. I wish I could give 0 stars.

I'm only basing this on my experience annealing, but this product seems to tell me when the right temperature has been reached. I guess I wouldn't know when or how much it was wrong, but it seems right.