Efficiency of "ice packs"

[tony1941]

I had always thought that those plastic blue liquid filled "ice packs" were filled with a solution of ethylene glycol, and that this was used to provide more"cold storage" due to a larger value of the specific heat. I have just discovered that ethylene glycol has a Specific heat of 0.57, (cf. water @1). What is the stuff in th epacks? What is the best way to make a "cool pack"? Is it best to rely on the latent heat of fusion of ice? .......or have I missed something?

[Space]

I think it's the latent heat that matters, not the specific heat.
What makes the ice pack efficient is mostly the heat it absorbs while melting, not the heat it absorbs once liquid and warming up.
You are supposed to make sure your ice pack is completely frozen before using it.