Diy ice packs

[Greenbeast]

I'm looking to create my own ice packs so that I get a custom for in my display cool boxes at farmers markets.
I have read some guides and its easy enough, I even have access to a commercial vacuum sealer to make a pro job of it.
My question is for the science boffins ; most articles refer to using alcohol or liquid Soap to prevent complete freezing but one did allude to the fact complete freezing removes the latent heat of fusion therefore requiring more energy to the.
Thoughts?

[dhaslam]

The gel or alcohol packs seem to be for medical use in order to have flexibility. 

[Greenbeast]

So would I be best sticking with pure water?

[A.L.]

hello,

- adding alcohol or soap will lower the freezing point , in proportion to the amount added ( IIRC molal depression of freezing point). I would expect the latent heat of fusion (on a kg or volume basis) to reduced slightly but not to much.

- I would just stick with pure water, leaving space to allow for expansion on freezing (or vacuum pack the ice  )