I saw this quote on the ray-way.com site:

We have developed a process that prevents our silicone nylon from passing a fine mist in a heavy rain. This process adds no weight, and is proprietary, meaning available only from us. Silicone nylon fabrics purchased elsewhere, even those of first quality, have a very high probability of misting-through. Misting-through can spoil an otherwise warm and dry night in stormy weather. For this reason we encourage everyone not to waste your money and sewing time making a tarp of silicone nylon purchased elsewhere.

My questions:

- has anyone else experienced this phenomenon? A couple years ago I was in
the Wind Rivers with my Tarptent
Cloudburst under _terrible_ conditions
(all night mixed rain/snow, temps around
freezing). I felt the "misting" effect
while it was raining (eventually I kept
wiping the canopy down with a towel).
The end result was a damp enough
sleeping bag that I was losing some loft.

- Is there any convincing evidence that
this is more than just condensation
being shaken off by heavy rain? Or
could it be actual micro-drops being
forced through the fabric?

- If so, does anyone have any
speculations as to what Ray's "proprietary" process is?
Maybe extra DWR or something?

Thanks,
Jim

I haven't experienced it directly, but there's a pretty lengthy discussion at whiteblaze if you want to search for it.

Basically it comes down to this - every waterproof material is only waterproof to a certain pressure. Above that pressure, water will find its way through. For lightweight materials like silnylon, sometimes rain can be hard enough to exceed that pressure, which results in misting.

I haven't seen any test data on this, though - other than setting up a tarp and aiming a strong hose at it. In a hammock people get very good ventilation under a tarp, and they've still reported misting during storms - and were convinced by the duration and amount of droplets that it wasn't just condensation.

If I had to guess, Jardine's treatment just increases the pressure rating for his silnylon. Finding a way to do this w/o increasing the weight has value - I wonder how it compares to Cuben or spinnaker fabric.

I've experienced this several times - each time an absolute driving, prolonged rain. However, I do not consider this to be a show stopper in any sense of the word. The mist is very fine and dispersed, and while disconcerting at first, insufficient to wet anything in the shelter. I use a down bag with a good quality water resistant fabric (Marmot Hydrogen), and my bag has never been wet. At worst, objects in the shelter might have a slightly clammy feeling after a long, hard rainstorm. The bottom line for me is, I am still using silnylon shelters, either ID tarps, or Henry Shires' fine products. I have no fear of getting soaked because of moisture coming through the fabric.

Cheers

Silnylon has a relatively low waterproofness (or whatever the term is). Simple pressure can push moisture thru the fabric and I've encountered this with silnylon stuff sacks. The pressure from a heavy rain would be sufficient to push moisture thru the fabric. HOWEVER, I think mist caused by the impact of rain and wind dislodging condensation on the inside of the fabric probably far outweighs the amount of misting from the rain itself. I spent a very windy and rainy night in a traditional 2-skin tent with a urethane coated fly last summer and experienced considerable misting which could have only come from condensation.

I would guess that Ray uses calendared fabric (if you can calendar silnylon without removing the silicone).

Silnylon isn't waterproof in the classic sense. The silicon impregnation of the ripstop nylon is like a permanent DWR that breaks the surface tension of water. This improves the water repellancy of the fabric but high-velocity water droplets can defeat this and you get your "misting". I experienced "misting" under a spinnaker tarp last year so I would guess that this is true of all silicon-impregnated fabrics... including Epic.

Jim Wood talks about waterproofness on his website, with some numbers.

Myself, backpacking/hiking in the rockies, it's far from my major concern ;)

http://jwbasecamp.com/Articles/DryGear/index.html

I keep a low density polyethylene 45 gallon garbage bag in my kit for times like this. They are nearly four feet tall, so you can use them for an emergency half-bivy, a raincoat, or sliced open, you have a small tarp or ground cloth-- at 1.4oz. It allows you to cover your bag from falling condensation, a night under a tree, or covering the bottom of your bag from the stream that magically appeared in your tent.

Edited by dwambaugh on 06/07/2006 12:12:11 MDT.

I love silnylon, but I've gravitated back to to lightweight polyurethane coated nylon because I don't like the misting. I have several silnylon tarps which I like for a variety of design reasons but what I really USE is my cape/tarp that goes over the hammock and serves as raingear.

With that said, I used a silnylon tarp with down quilt on the AT in '03, the monsoon year. I didn't die or get wet. But feeling that mist coming through is disconcerting. I plan to do the AT again in '07 and will use a PU coated cape this time.

Anyone know if the heavier silnylon used in the GoLite Hex 3 has the same misting issues, or does the thicker fabrix alleviate this?

I was in a friend's Hex 3 in a very windy snowstorm, and we could see the moisture coming down from the walls. I couldn't say how much was condensation, but there was probably too much moisture for it to all be condensation.

These winds were gusting to over 100mph and the Hex withstood it for several hours...I was very impressed with its performance that night.

Edited by Just_Jeff on 06/08/2006 06:56:36 MDT.

In my own experiments I have found, in order
of waterproofness under pressure, (starting
with the most waterproof )

200 denier nylon with 3 oz urethane coating
(used in dry bags as it is a thick enough coating
to be heat sealable)

200 denier nylon with 1.5 oz coating urethane
total weight about 6.5 oz per yard square

70 denier nylon with 1 oz coating urethane
total weight 3 oz per yard square

70 denier nylon with Goretex XCR 2 layer or
Paclite 2.5 layer laminate 2.1 oz per yard square

30 denier nylon with .2 oz silicone coating
total weight 1.3 oz per yard square

30 denier nylon with .2 oz blended silicone
and urethane coating
total weight 1.35 oz per yard square

Spinnaker "pro"

70 denier nylon with .25 oz urethane coating
total weight 2.25 oz per yard square

Standard "white" Spinnaker

The fabrics with over an ounce of coating
withstand high pressure. The others
will have some drops form under high pressure
but are very waterproof under average rain
conditions. I have yet to hear from someone
who speaks of this "misting" in the tarps
and fabric I have sold. (Not that it doesn't
happen, but I don't think it is common)

I don't believe Ray can do better
without increasing the weight of the fabric
with more coating.
Note that spinnaker cloth
is calendared.
The 30d silicone coated fabrics have
3 times the tear strength of the heavier 70d urethane fabrics at half the weight .

You could double up on the silnylon fabric for the weight gain would need to incur to switch to a more waterproof urethane coating.

As others have noted, misting does sometimes occur in hard rain storms with standard 1.3 oz silnylon (which when new, is only waterproof to 1-2 PSI). If it bothers you, the good news is that it's fairly easy to eliminate by applying a thin coat of the slurry discussed in this article to your tarp or canopy of your shelter.

Rather than using the 1:3 mix (sealant to mineral spirits) for silnylon floors that's discussed in the article, a more diluted 1:5 mix should work well for canopies while adding a bit less weight. The treated shelter, depending on size, will probably gain only an ounce or two.

It's probably also best (if practical) to apply the mix to the underside of the canopy since the dried treatment will reduce the slipperiness of the silnylon fabric a bit. There's an advantage to having the outside silnylon surface as slippery as possible since it helps accumulating snow slide off onto the ground.

Also note that this treatment only works for silicone impregnated fabrics and will not bond with PU coated surfaces.

Edited by jwood on 06/08/2006 13:43:37 MDT.

Oh, and silnylon from the more common US
source is hot calendared.

Jim Woods' article mentions that PU tent floors usually have a hydrostatic head in the range 5,000 mm to 10,000 mm (higher is better/more waterproof). The article goes on to say that 30D silnylon generally has a much lower hydrostatic head, between 700 mm and 1,400 mm. Consequently silnylon tent floors can leak under (body) pressure. The British tent manufacturer Lightwave claims that the silnylon used in the canopy of the t0 ultra has a hydrostatic head of 5,000 mm. If that's correct it would solve the misting problem. Oddly enough, the floor is PU, also rated to 5,000 mm.

Edited by benwald on 06/08/2006 20:24:51 MDT.

I will likely have some 70d ripstop with a .5
ounce coating of silicone and urethane blend
soon. This should make a bit more durable floors
than 30d silnylon at less of a weight penalty
than heavycoat 70d urethane. It shouldn't
be as slippery as pure silicone coatings either.

It would be great to see any sources for PSI of
coatings. I can only compare them one to
another. Perhaps there is a more ideal
amount of coatings or blend of coatings.
Where did you get your data Jim?

Reading this thread has got me wondering about silnylon as a bivy bottom/floor. I'm about to sew one, and wondered what other people's experience is. given that oware makes em, and shires tarptent floors are silnylon, I figured it'd be ok, but now I'm wondering if I need to worry about water soaking up through it. what are you all's experience w/ that?

Did you want your floor to be completely waterproof or water resistant?

I made a Bivy out of DWR nylon for the top and Silnylon for the bottom. I use mine in concuntion with a poncho tarp to keep the bulk of the rain off .... Unless you have a river running under your tarp or you're laying in a puddle, you should be ok.

Yeah, I was planning to use it w/ a tarp, not as sole shelter in serious rain. Although I suppose that doesn't necessarily mean there won't be a river running under... :-)

Edited by johnbrown2005 on 06/09/2006 13:38:42 MDT.

David -

My data regarding the water resistance of silnylon was collected from a variety of sources. I should note, however, that silnylon is kind of an odd product about which not very much info is actually published, at least on the Internet.

One of the few companies that does make some specs available is Performance Textiles (http://perftex.com). Their "Soar Coat" product is pretty much a "standard" 30 / 40 denier silnylon. I ended up calling the company to discuss water resistance, since that particular spec is not listed on their website.

Another source, "Ayce" at thru-hiker.com, probably knows at least as much about silnylon as anyone else in the backpacking world and has confirmed the 1-2 PSI rating for "standard" silnylon. If you search his forum, you'll find the issue discussed in multiple threads.

As a further check, I built my own crude hydrostatic head testing rig that consisted mostly of a 10 foot section of PVC pipe to which I affixed silnylon samples (at the bottom when the pipe was oriented vertically). I'd slowly fill the pipe with water until the fabric sample began leaking, then would measure the height of the water column that produced the leakage. I found that the 1-2 PSI rating was about right for my silnylon samples when new, but also observed that the water resistance of silnylon can deteriorate after it's used for a while.

It's worth noting (as you already know, but others may not) that some newer 30d fabrics are now being treated with both silicone and polyurethane. The Sea to Summit Ultra Sil dry bags and the rain flys of lightweight tents like the MSR Hubba series are examples of applications using this dual-coated fabric.

The double coating adds weight, but improves water resistance to a degree (but not a lot in some cases if it's very thin). It also makes it possible to heat-tape the PU-coated side of the fabric—not possible with straight silnylon since it's so slippery. It further improves fire retardency enough that tents made from the fabric can be sold in those jurisdictions (seven states + Canada at last check) whose laws make most silnylon tents technically illegal because silnylon doesn't measure up to their tougher fire retardency standards. As most backpackers know, standard silnylon will burn if exposed directly to a flame.

So far, I've tested only a single sample of this dual-coated fabric (the new Ultra Sil dry bag) and was not very impressed. You can see the leakage problem here.

Edited by jwood on 06/09/2006 15:49:12 MDT.