How do you keep your foam sleeping pad dry?

My understanding and according to the manufacturer's website, theramrest foam pads (Ridgerest, Z-lite) are closed cell foam. Their inflatable pads such as the prolite are open cell foam inside an airtight shell. I have cut/trimmed several ridgerests and z-lites and never noticed that the fresh cut edges absorb any measurable amount of water.

To the OP, I would think that trying to keep the pad dry is moot since it likely does not provide enough insulation to justify carrying it. If you are looking for an UL pad option get a piece of 1/8" thick Thinlight from GG and trim it down to torso size, you could prob get it sub 2oz relatively easily.

*Edited for spelling*

when you cut a roll down you've damaged the edge cells, they are now capable of absorbing water.

the reason the zlite, and it's ilk do not have this problem is they are molded into their sold shape, so there is no cut edge to damage the cells.

scratches, tears, etc. can damage the cells, which can then allow them to absorb water. don't let your CCF pad get damaged!

The edge of the CCF pad I carried had absorbed a small amount of water, which is what brought this question up.

It sounds like if I had rolled it out, wiped it off I would have been fine to sleep on, the minimal edge absorption would not have been enough to worry about.

How difficult is it to wipe dry a zlite/etc after being soaked in a driving rain? I imagine more so than a flat CCF pad due to the crevices?

I've never had a problem with cut down CCF pads absorbing water, but I haven't used them all by any means. I wonder if they could be sealed/repaired with Seam Grip or silicone?

An open cell foam pad is identical to a synthetic sponge and would be very good at absorbing water. I would wring it out and hope it drys completely from there.

The foam insulation for the Hennessy Super Shelter is open cell foam and needs to be protected from rain. When in place, it is covered by the under cover and Hennessy recommends using a space blanket on top for added insulation and I imagine the space blanket also avoids absorbing perspiration/condensation too. It comes with an open ended stuff sack, so adding a plastic bag helps to keep it dry.

For a larger open cell foam pad I would just use a trash compactor bag. You could stash your pack in it overnight or use it as a bear bag.

I carry my closed cell sleeping pad rolled up on the outside of the pack exposed to the rain. I also use it as a back pad and as a raincoat so it is often wet and usually sweaty. Here are a few more suggestions for dealing with the surface moisture that gets onto the pad.

(1) The surface of these pads aren't all the same. I look for pads that have a harder slick surface rather than a soft rougher surface. The former is much easier to wipe dry with a hanky than the latter. The cheap pads often have the surface I prefer.
(2) I avoid the pads with ridges, bumps or waffle patterns. They collect the water and it is harder to wipe the surface dry. If left for 3 days filled with water I could envision a mosquito hatch.

(3) Foil surfaced closed cell foam pads are the easiest of all to wipe dry with a hanky but the foil eventually wears off and tears.

(4) If the pad is too wet for your comfort, covered with pitch or mud, impregated with poison ivy (happened to my wife) or covered with bear scat you can always slip it under the floor of your tent rather than bringing it inside with you.

Small thin office sized garbage bag:
-Weight Penalty: ~0.5oz
-Keep it packed until it starts raining to prevent tears

Silicone Waterproofing Spray:
-Weight Penalty: A gram tops
-Fairly inexpensive, and waterproofing things around the house (sneakers, aprons, dogs, etc.) is hours of fun.
-Easy to maintain, if you're out say 150 to 200 days a year, you would probably have to touch this up every six months or so
-Only bad part is if you miss a spot, and it gets wet, you could be promoting mildew grow in the foam (think rain on cars' leather seats)

I bet latex paint would also work very well for this specific application at a fraction of the price of silicone spray (but I can't think of any other piece of gear I'd trust that with)

Sorry, I'm late on this. I missed it before.
Closed cell foam can absorb some water. Not a lot, but enough to make things damp if it can't be allowed to drain and air out before you lay your quilt/bag on it.

In 100% humidity conditions like you experienced, it probably wouldn't have dried out.

The texture of most closed cell pads is rough and the rough texture has more surface area to hold water. The slick surface of some pads help, but this goes away when they start getting rough spots from wear.

Rubbing it with a dry cloth would have helped a lot, but who has a dry cloth on such a trail:-(

If it is 100% humidity(raining), said CCF pad will have gained weight anyways on its surface. Same with your sleeping bag/clothes etc.

On a CCF pad, you gotta shake it out, likewise this is why I carry my CCF pad on the BOTTOM or TOP my pack, not generally strapped on the side. This guarantees I don't even have to shake it out as there is a guaranteed dry surface at all times. Note I do NOT carry those crappy CCF pads made by Thermarest with all of there moronic cups and ridges just waiting to open their arms and catch all available free water.

PS. In summer and no rain, I will take a half Z-rest as they make quick wonderful chairs, sunshades, cooking wind screens, but in rainy season or a long treck? NO!

If it is raining that hard, then you better have a rain cover/poncho to go over your pack. If you have one of those nice WP packs or just use a packliner like most folks do, then a single end cap bag that tucks under the strap holding your CCF pad rolled works as well. I will admit I did this way exactly once and decided to ditch the weight as a tightly rolled up CCF foam pad will maybe be wet on the outside 1-2 inches on the ends even in a downpour if carried under your pack or on top of your pack. Key, CCF pad MUST be TIGHTLY rolled. If you are trying to carry your CCF pad without a strap and just "get by" by using the straps on the bottom of your pack, you sir will be SOL generally.