Ice packs for cool bags: your recommendations please.

[Polar Bear]

Looking for that bag to help keep things cool at camp I managed to land a Red Original 30 litre bag at a decent discounted price.  Now I need to buy some ice packs and would appreciate the wisdom and experience of the YACF massive please.

I am looking for packs which stay cool longest and are also robust.  We are likely to have items such as cheese, yoghurt and milk in the bag as opposed to bottles of beer.  Boring I know but that's just the way it is.

[Kim]

Shirley it's just latent heat and thermal mass of something that's approximately water, so for an equivalent mass performance isn't likely to be very different^[1].  I'd choose whatever's a convenient shape (IME the limiting factor is finding room for it in the freezer before use) and is reasonably durable.

Gel packs that remain flexible are useful for injuries and smaller coolbags.

FWIW we've got some of those rigid plastic packs with liquid that freezes solid (presumably water with a bit of glycol) in them, just like the ones my parents had in the 80s.  They're about 20 years old and still work fine.

A useful trick is to make use of whatever other thermal mass you have to hand.  Bringing a tin of beans?  Cool it down in the fridge and pack it in the coolbox so it can help keep the milk cold until you use it.

The real challenge is what you do on the second day, unless you're at the sort of campsite that provides freezing facilities.  Usually that's buying a bag of ice cubes from a supermarket, and the coolbox turning into a poolbox as it melts (not sure how well that works with a bag).  Otherwise you're into active refrigeration, which is the realm of ammonia-cycle gas fridges or electric hookups.  Our coolbox has a peltier thing in the lid, which is sufficient for keeping it at reasonable fridge temperatures indefinitely, iff you can feed it the 100W or so it requires.


_{[1] Obviously an ice pack that was less effective at transferring heat would stay cool for longer, but then you're getting less cooling from it.  In my mind, if you're going to insulate something, it's better if it's the outside of the coolbox.}

[Mr Larrington]

Back in the early 1970s we had a Thing which was a metal cube wrapped in some kind of porous foam.  You poured water into a divot at the top and evaporative cooling chilled the interior to preserving-milk temperatures.

[Basil]

Back in the early 1970s we had a Thing which was a metal cube wrapped in some kind of porous foam.  You poured water into a divot at the top and evaporative cooling chilled the interior to preserving-milk temperatures.

I remember when I was a small, my mother kept the glass milk bottles standing in a washing up bowl of water with a wet tea towel draped over. Tea towel draped into the water kept it damp.

[Polar Bear]

Back in the early 1970s we had a Thing which was a metal cube wrapped in some kind of porous foam.  You poured water into a divot at the top and evaporative cooling chilled the interior to preserving-milk temperatures.

I remember when I was a small, my mother kept the glass milk bottles standing in a washing up bowl of water with a wet tea towel draped over. Tea towel draped into the water kept it damp.

We had been using such a contraption, a round metal pot with enough room for a litre of mils, a bottle of wine and a sealed tub of yoghurt. 

Problem is, it's not really car friendly ...  😉

[aidan.f]

A useful trick is to make use of whatever other thermal mass you have to hand.  Bringing a tin of beans?  Cool it down in the fridge and pack it in the coolbox so it can help keep the milk cold until you use it.

Frozen milk. Adds or is that subtracts? latent heat of fusion. Don't freeze tins of beans, they go mushy..found that out after a very cold week inna bothy.

[canny colin]

 I used frozen 500 ml sports bottles of flavoured water , old bottles re filled off a big bottle , with a bit more space left in them . Taste nice once defrosted .

[fruitcake]

I use frozen water / hummus / butter / milk / soup / curry / chilli / casserole / (portioned up in single serving sized water tight tubs), all of which, when thawed, can be consumed. It's no extra weight if you're transporting food and drinks anyway. If the tubs are small enough, you only need to open the one you'll use that day, the rest can stay sealed, which is likely to delay their thaw.

Fringe benefit of transporting food and drink frozen is you know it won't spill in transit.

[Polar Bear]

Freezing 1 litre milk plastic bottles is a good idea.  We have binged such in the freezer in the past so a couple of them to start off the trip would be good.  I can then perhaps reuse the bottles with water and a taped closed top for fe-freezing using the facilities on site.

Another alternative might be these soft bottles that trail runners and the odd long distance road runner seem to have in their multi-pocketed running vests. 

[fruitcake]

  Take a spare cap for the milk bottle just in case you drop the cap or lose it. Tetrapak containers can also be frozen and they tessellate.