compression sacks / storing sleeping mats

[Si]

why doesn't someone invent one that compresses after rather than before you stuff you sleeping bag or tent into it....would make life so much easier and I'd have more finger nails left. 

I've now given up using the bag that my sleeping bag came in, just use a much bigger bag and then put straps round it to ensmallen it.

-

Talking of bags - both my self inflating sleeping mats say "do not store in bag".  I, of course, stored them in their bags as I've no room to store them unbagged, and now they don't self inflate....which is not a problem because it only takes a minute to blow them up.  But when I bought them they were in stored bags in the shop....so if storing them in bags harms them how come they work fine when you buy them?

[rr]

My last two sleeping bags spanning 25 years have come with compression sacs, stuff, close then squash.

[Kim]

Talking of bags - both my self inflating sleeping mats say "do not store in bag".  I, of course, stored them in their bags as I've no room to store them unbagged, and now they don't self inflate....which is not a problem because it only takes a minute to blow them up.  But when I bought them they were in stored bags in the shop....so if storing them in bags harms them how come they work fine when you buy them?

I think it's a matter of time.  If you store it compressed, then it'll take unfeasibly long to self-inflate.  When you buy it new, they warn you of this in the destructions.

I expect that if you unrolled it and opened the valve it would eventually inflate itself.

Sensible places to store unrolled mats are a pain.  My Airic lives vertically behind a (permanently open) door, maybe you've got a bookcase or something?

[Dibdib]

I wonder how much of it is also the number of compress/uncompress cycles, maybe damaging the foam's springiness.

Mine live flat under the spare bed, or up the side of a cupboard.

[hellymedic]

I don't definitely know but I would guess the moisture in breath has an adverse effect on the foam.
Brand new mats are probably pretty dry.
My ThermaRests are at the side of a wardrobe.

[Kim]

I don't definitely know but I would guess the moisture in breath has an adverse effect on the foam.

That's certainly known to cause things to go a bit manky, but I don't think that it really matters other than smelling when you deflate the mat.  (It's contraindicated with down-filled mats, which is why they tend to have pumps of some kind.)  Allowing the moisture to escape is another reason to store the mat unrolled with the valve open.

[Si]

Mine live flat under the spare bed

Can't see the cat allowing that for long! 

Moisture, yes, hadn't thought of that....

[rr]

Mine goes unrolled under a bed.
Stepping back to my previous life as a polyurethane foam development technologist, I once tried to make foam to cascade designs spec. They specified a very low compression set which was very hard to meet.
If you leave foam very squashed for a long time, it will not totally recover, moisture will accelerate this degradation. Foam does get softer under constant flexing.
That said the foam in these mats is not there to provide padding, it is there to produce the self inflating effect and to provide at medium to damp air movements which adds comfort and insulation.

[andrew_s]

That said the foam in these mats is not there to provide padding, it is there to produce the self inflating effect and to provide at medium to damp air movements which adds comfort and insulation.

The foam is there to hold the mat in shape. Self-inflating and insulation are bonuses.