Following on from my post about keeping the booze cool, I was sent an email about the Easicool. I'd not come across one of these before. It's an interesting alternative to the usual coolbox using evaporation to keep the inside cool. It's a box surrounded by a porous material (something similar to plaster of paris as far as I can tell) which you pre-soak in water. You then place freezer packs or cold food and drink (or both) inside to pre-chill the box. Then you are ready to go. The water needs topping up each day but only with a cupful or so.

The reason the evaporation keeps the inside chilled if I remember my 'O' level physics correctly is that the evaporation requires the water to change state from liquid to gas and this requires energy that energy is drawn from the box in the form of heat so keeping the inside chilled.

There are a few things to note about this type of coolbox. Firstly it's not very common, the Easicool seems to be the only one on the market. Secondly the pre-soaking is really important and if you don't sit it in a bath of water overnight it won't work. Thirdly, they are by all accounts very heavy. Lastly it won't make the things you put inside cold, it will just stop them from warming up much like a coolbox does. So you need to put things into it already cold.

I would guess they fell out of favour (they were more common in the '70s)  because they don't offer much benefit over a standard coolbox but they are a more hassle and considerably more expensive around £100. Given you can get a 3-way (12v/mains/gas) fridge for a similar amount they seem over-priced for what you get.

Thanks to alule for the tip off.