A simple click of a metal disk inside the pack immediately warms it. It gets nice and warm and stays that way for quite a while. The problem is you have to boil it in water to get it back to a useful stage. It’s pretty big so I use my pasta pot. It takes about 20 minutes of stirring and watching the pot so it doesn’t stick to the bottom or sides.
I put a washcloth in the pot so it doesn’t stick. But, it’s a big PITA to boil it and more than once I thought I had it completely done only to have it go solid again after it cooled down (meaning there was a little bit of gel still hiding somewhere). I’ve used it maybe 3 times and now it just sits in my closet. I use my beanbag heating pack WAY more.
I’ve had these in the past when my kids were younger and in sports. They seem like such a good idea…until you have to boil them! What a pain!! I was boiling mine 2-3 times a day! It is SO inconvenient! It seemed like I had a big pot of boiling water on the stove constantly! The kids did like them but the time and energy spent getting them back to gel state just became too much and these sat in a drawer until I finally decided to sell them at a garage sale! Just not worth it to me.