Gossamer Gear Thinlight Mat (grey, top) and Generic EVA 30 Mat (blue, bottom).
This mini-review is part of Part 2 of our survey of airmats. We have two thin closed-cell foams (CCF) mats here: a (grey) Gossamer Gear Thinlight mat nominally 1/8" (~3 mm) thick and a (blue) generic EVA 30 mat about 4 mm (0.16") thick.
Neither of these mats is intended as a sleeping mat by itself. They have two purposes: to supplement a conventional mat when the season gets cold, and to line the floor of a tent when (say) camping on snow. As such we have not measured their R-value in isolation; rather we have measure the R-values when used as an overlay on top of a smooth cored foam mat and when used as an overlay over an air core mat. The results do depend on what sort of mat is underneath the foam.
If you want to use one of these mats just by itself, you can use the R-values for the smooth mat case as indicative.
We will combine the two foam mats into one table, as they are basically very similar. Note that 'gsm' means 'grams per square metre.'
As noted above, the R-values for the foams were measured using a smooth mat and a tubular bat as the base layer. It was very quickly obvious that what mat was under the foam had a large effect on the apparent R-value. We interpret the difference as reflecting the smoothness of the mat surface; a flat cored foam mat leaves no room for any extra air between the foam and the mat, but a tubular mat leaves lots of small air volumes between the two. This extra air between the foam and the mat is a good insulator of course. So using a foam mat on top of a cheap air-core mat might be a useful option to boost the low R-value of such a mat.
There is also a difference between a generic EVA-30 foam and the Evazote foam used in the Gossamer Gear Thinlight mats. This is basically a function of the design of the Evazote foam. To quote the manufacturer, it is a 'closed cell cross-linked ethylene copolymer foam. EVAZOTE foams are tougher and more resilient than PLASTAZOTE foams and are mainly used in a wide range of sports & leisure and footwear applications.' It does provide significantly higher performance than the stock EVA-30 blue foam quoted above.
Ordinary EVA-30 foam is 'made from Ethylene Vinyl Acetate and blended copolymers. It has a high level of chemical cross linking. The result is semi-rigid product with a fine uniform cell structure that is suitable for use in a wide variety of situations and applications.' The web site given here is in Australia, and is where the author's blue foam comes from. The '30' signifies that the foam has a density of (about) 30 kg per cubic metre. The foam is actually available in a wide range of densities, from 15 to 400 kg/m3: the higher densities are rather rigid.
The shiny surface on the blue mat is actually the skin of the huge block of foam, before it was sliced up. We have found that while the cut surface of a closed cell foam can get dirty, this 'skin' is extremely resistant to water and dirt. Yes, using the skin does add a bit of weight to the mat, but not very much.
This was not measured for the foams. The foams are not all that strong, and the cut surface of the foam does have a very high coefficient of friction anyhow. The combination suggested that the foam was likely to rip under the test conditions. Field use suggests that the foams are strong enough that they will survive, but will not go skittering across the mat or the tent.
The photos here are taken from Will's field-testing of two of the mats in this series: in both cases he was using a Thinlight overlay.
Comments by Will Rietveld
Note that the Thinlight pad conforms to the curvature of the pad underneath. Remarkably the Thinlight pad stayed in place quite well and did not shift or slide off the underlying pad when I was turning over during the night. I found that the Thinlight pad significantly extended the warmth of an air-core sleeping pad, adding 5 - 8 C (10 - 15 F) of thermal comfort.
Comments by Roger Caffin
We (Sue and I) have used the blue foam mats for many years, in the snow and in milder weather. They have often been used to line the end of the tent under our legs and feet when we were using a light 3/4-length mat such as the Therm-a-Rest ProLite. It is also worth noting that we often used one of these blue foam mats to sit on the snow at morning tea time and lunchtime, although we would normally also have a sit-mat there as well. Without the extra sitmat we found we were getting just a bit cool underneath. The advantage of the foam under these conditions is the ease of spreading it out and that it barely compresses under load. I have also used the Thinlight mat over a MontBell UL120 cored-foam mat at temperatures down to -8.6 C (16.5 F), under a quilt. It saved the day there.
This is a mini-review in the 2011 Lightweight Airmats State of the Market Report. The articles in this series are as follows (mini-reviews can be found in Part 2), and a subscription to our site is needed to read them.
- Part 1 covers the basics, testing methods, and lists all the mats in the survey.
- Part 2 examines the actual mats, and the performance of each mat tested.
Disclosure: The manufacturers provided these products to the author and/or Backpacking Light at no charge, and they are owned by the author/BPL. The author/Backpacking Light has no obligation to review these products under the terms of this agreement.