RE: Re: Ultralight synthetic base layer

Hi Bill,
                I am not going to recommend anything. I would prefer the silks, based on past performance. But, silk needs to be laundered like down, otherwise it breaks down rapidly. 'Nuff said about overall maintenance. Durability is only fair, as Cara Lin says. Rather than maintaining strength when wet, they will become a bit weaker.  Reliability is good, as with all long johns. Again, CL was saying about wearing worn silks with no problems.
                Synthetics are heavier...about 35-50% heavier than silk.  Typically, two UL layers of silk at about 7oz will be warmer for the weight than a single layer of light weight synthetics at about 13-15oz. While you can certainly use a single layer of fish net long johns, they are not of any great significance for warmth when worn alone. They need to be layered under something: shirt, VB, other long johns.  In cold weather, this isn't a problem.
                I would suggest that *any* synthetic will not perform as well as a natural fiber under a VBL. Typically the plastic does not absorb water to any significant degree. Much of the comfort of sleeping in a VBL is the absorption they supply. A typical set of wool long johns (while heavier to carry) would keep you fairly comfortable in a VB sleeping bag. Under very similar conditions, you might experience wetness and feeling dank/clammy/cold with synthetics.  In either case, the problem is to get them dry enough to sleep in the next night of near zero F weather. Fishnets will dry as quick as quickly as light silks. Nothing dries that well at 20-40F and near 70-100% humidity, though. Below that the air is always very dry. I would suggest bringing two layers of silks and alternate nights in these. Hanging near a fire (even 8' away works for drying from IR) will let you wear one layer and dry the second, and/or putting one layer over your bag to dry as you sleep. The absorbed water, usually a large portion is water vapor, will dissipate quickly. Any ice that does form, will be a problem, of course. This is actual water...the liquid and not the vapor gas.  But you would have heavier build-ups of ice with synthetics, compared to UL silk or light merino wool. Fish nets provide a large air flow for drying. So, while I have never used them, I suspect they would also dry fairly quickly, provided they are not iced up. Typically, 2 lighter layers will dry at about 30%-200% quicker than a single heavier layer. (I believe this is a log difference, but I have not done any research into drying times...Roger Caffin might know more having worked in the textile industry...)
                My thoughts only . . .
                                jdm
James D. Marco
302 Mary Lane
Ithaca, NY  14850
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