I'd like to make my own hand warmer, so I bought sodium acetate and made a solution. When I put some solid acetate, it starts solidification. But, I'd like to close it in some kind of container and initiate solidification with fixed trigger located inside. I read some articles about the trigger. It's usually a metal disc or a tiny stick which releases small crystals when is pressed. How does it work in details and how could I make it on my own?
Thank you in advance for any answers. [;