“Misting” Silnylon!

[David Ure]

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[Rog Tallbloke]

>Not a good idea if the fly is already wet, however. Additional pressure on a wet fly from the spaceblanket could push the water through even faster.

Well, that's not my experience, I'd rather a couple of ounces of what was already on the fly came through than a few more pints overnight anyway.

[Roger Caffin]

> > My experience is that the misting isn't from water pushing through the fabric – it's from condensation building
> > up on the inside of the silnylon and then getting knocked off by the rain hitting the outside.

> That's probably true in most cases, but for this experience the "waterfall" started immediately, within 2 minutes
> of entering the tent, so there wasn't any time for condensation to accumulate.

I am going to agree with Steve here. It is extremely unlikely that falling rain could create enough hydrostatic head to push that much water through silnylon. Even torrential rain. The outside surface of the fabric gets a film of water on it which buffers the raindrops.

In torrential rain the fly will cool fast, helped by the fact that the rain is often significantly colder than the ambient air. Of course, your being inside the tent with some damp clothing is going to create ideal conditions for condensation to happen within seconds. The rain on the warm ground will do the same.

Take a cold bottle out of the fridge on a humid day and see how long it takes for condensation to form. It can be very fast.

You will note that some people say it didn't happen to them. A distinguishing feature between the two cases is often that the 'torrential rain' is on a very still humid day, possibly warm, while the other cases are on less humid days, possibly cooler, with some wind.

Taking a step back from the details, to what sort of tent is suitable. This is a subject which has been thrashed over many times here. A double skin tent (NOT a netting inner but real fabric!) is generally the recommended solution for these conditions.

My 2c.
Cheers

[Tad Englund]

I'm with Roger on this- Last winter I was testing a down bag in my back yard (Seattle area). It was about 40 deg F. and almost 100% humidity. The ground was moist from a resent rain and after pitching my tarp at normal height (probably higher then normal), with no wind, after getting into my bag I noticed a mist coming down as each rain drop fell on the tarp (it started raining after I set up the tarp). I thought it was coming through the tarp as described above.
I tested the tarp the next day with the hose and couldn't reproduce the effect. The hose was squirting far more water then the rain.
It was the great moist Seattle air on both sides of the tarp. No mist, just condensation.
In these conditions there is no way around it, single wall double wall or Tarp. BTW, the bag (Marmot Helium) did great. The moisture fell on top of the bag, beaded up and didn't have any noticeable effect. The outside fabric was moist, the inside dry. Seams like a good purchase.

[Franco Darioli]

" My experience is that the misting isn't from water pushing through the fabric – it's from condensation building up on the inside of the silnylon and then getting knocked off by the rain hitting the outside"
That is true most of the time, as I have had some heavy all night rain on my TTs (!) and stopped the misting by wiping the inside of the fly dry, sometimes I had to do that only once, others two to four times .
However a comment about "pressure" on a different thread, reminded me of one occasion when the Contrail and the Rainbow were set up side by side weathering a storm at the bottom end of the state. The Rainbow remained completely dry all night, my Contrail had some mist from a rhythmically falling (every few minutes ?) big blob of rain from an overhead branch (several meters above) . In spite of the loud noise from the wind and heavy rain, this "blob" was very noticeable and caused a small spray every time it hit the fly. (I put my rainproof jacket over the sleeping bag in that area and went to sleep).
So given the right conditions , water will indeed penetrate the 1.1 oz silnylon, but most of the time a good wipe will fix the usually reported "misting".
Franco

[David Ure]

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[Joseph Reeves]

After years of using tarps in Southeast Alaska' Tongass Rain Forest, I concur with those who think the mist is condensation. We've huddled under our tarps and pyramid in more than a few deluges without seeing water seep through.

see http://www.flickr.com/photos/umnak for more pictures of tarps.

[Lynn Tramper]

I dont' know how much a hose test will really tell you for the reasons that Roger pointed out. Unless the water was the same temperature as the air, it would quickly chill the tarp causing condensation on the underside. The real test would be to use a controlled environment where humidity was close to nil and water and air temp were the same. Short of that we can only speculate. I have always assumed the water we see on the inside of the tent in a deluge is in fact condensation being knocked off by the force of the rain, but don't really know for a fact. I do know heavy rain and humidity usually go together, and in most cases I've been in the rain seemed colder than ambient temps.

[David Ure]

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[Franco Darioli]

The size of the raindrop and it's velocity will determine if it will penetrate or not. That is why some will never experience "misting" from penetration but only from condensation.
Raindrops can be from 0.1mm to 8 mm thick ( 0.2 to 5.1mm according to other sources), typically the bigger the raindrop the faster it will fall.
Franco

[Miguel Arboleda]

Obviously my observations of the water inside the tent during the deluge wasn't measured or scientific, so I can't really say what was truly happening, but I do have my years of earlier experiences with silnylon shelters to compare this one experience with. I've experienced misting many times before and never before felt that it was threatening the safety of my gear. All times before the misting was very light… sort of like a very fine atomizer… and while it made things damp, it never got everything I had wet. And I never had the fabric literally dripping all across the surface with water droplets. This time literally everything was soaked within half an hour and our sleeping bags would have been severely compromised had we not stuffed them back into the pack liners. We both wore our rain jackets inside the tent, which in 38 years of camping (in which here in Japan I've experienced a lot of rain, quite a lot of it very hard) I've never had to do before due to condensation in the tent (except one time when the unsealed seams of my Rainbow leaked badly), and I'm sure most of you with your own silnylon shelters don't have to do either.

The size of the raindrop and it's velocity will determine if it will penetrate or not. That is why some will never experience "misting" from penetration but only from condensation.

I think Franco is right there. Anyone who has experienced rain in Japan will know what I am talking about when I say it rains "hard" here. Every year dozens of entire mountainsides in Japan fall away due to the horrendous rainfall. Last year in Kyushu one village got 800mm of rain in one hour. Every winter the Japan Sea side of Japan gets an average of three meters of snow… the village where a friend of mine lives that I visited last May once got seven meters (I'm not kidding; I saw the pole with the notches measuring the level of snowfall every year) of snowfall one winter! Just imagine what kind of precipitation is necessary for that to happen!

So I don't know. It seems most of us here are just speculating. Is silnylon actually permeable? Or is all "misting" due to condensation? Are there different grades of silnylon (I've never had a misting problem with my Akto or Golite Hex)? Does the angle of contact by the raindrops affect misting? Does aging silnylon (my Squall 2 is about 5 years old) become less waterproof?

And I want to reiterate Ben's question: what are the alternatives when a shelter's fabric fails? Usually I carry a bivy, but not this time. If worst came to worst and if water had begun to get in I could have covered the top portion of the sleeping bag with my rain jacket while stuffing the end of the sleeping bag into my backpack. And if the tent fabric itself had ripped or fallen apart (I recently experienced how fragile old nylon left in the sun can be when I poked my finger through the canopy of an old tent and my finger went through like butter) I could have pulled up a big pile of bamboo grass growing all around the camp site and gotten under that for protection. It would have been wet at first but quickly warmed up. All the sika deer that we could hear barking all night long all around us slept in the bamboo grass to stay warm.

But I really would prefer to rely on my shelter!

[Miguel Arboleda]

Allison, as a Kiwi you must know a lot about dealing with endless rain. I think Japan and New Zealand are very similar in terms of climate and terrain, both are influenced by polar weather patterns, both are long, mountainous islands off the east coast of a continent… very rainy with very steep, volcanic mountains. You mentioned the Nallo 2. For two people would you say that it is the best light shelter for the conditions you encounter? Do you ever use a tarp? (I think I would go with a tarp in mid-spring and late autumn in Japan, but the summer rains and powerful winds just shoo me off). What do you use for a solo shelter?

[Chris Jackson]

Miguel, do you have access to a high-pressure hose? With that you could test whether the silnylon leaks at high pressure. I suspect that silnylon with a sub 1000 mm hydrostatic head does leak under pressure. It's telling that, in the wet environments of Sweden and the UK, tent manufacturers use silnylon with a higher hydrostatic head; Hilleberg 2000 – 3000 mm, Terra Nova 4000 mm and Lightwave an astonishing 5000 mm. See also this recent thread at Outdoorsmagic. It claims that 1000 mm silnylon will leak in wind-driven rain at 35 mph, and recommends at least 3000 mm. It also suggests that Golite's silnylon has a 3500 mm head.

[Rog Tallbloke]

Chris:
This is correct, and is the reason I bought a Hex3 for 2 person camping in the UK climate.

When I was younger and short of money, using old PU coated flysheets which were past their leak by date, I certainly found that putting an impermeable barrier such as a spaceblanket or polythene sheet over helped a lot. Spaceblanket is best, because the surface tension of the water already on the fly makes it cling effectively.

A Terra Nova may weigh a bit more than an ultralightweight tent, but the difference is less than a couple of sodden down sleeping bags…

In search of lightness and watertightness I'm going the spinnaker route now with a GG Spinnshelter.

[Mark Verber]

Earlier this year we have a tarptent squall2, a MLD Superfly in spinaker, and a GG The One set up in a storm with 35+mph winds and where we got several inches of water in a couple of hours. At a different time we hit the shelters with a jet of water from a hose. This was done on a warm day with low humidity.

Squall2: light misting at times. Sideblown wind soaked the netting but there wasn't noticeable spray through the netting. Significant water gets through from the hose.

The One: The first time out it hadn't been sealed yet, so we did have some leaks from the seams. Otherwise it did well. No misting in the field. When hit with the hose I could see misting much like what I saw in the squall2 during the rain storm, but less than the squall2 when hit by the hose.

Superfly: no misting in the field. Wouldn't have known there was a storm outside except the hard rain hitting the walls made quite a bit of noise. Hose test didn't seem produce obvious mist though there might have been very slight misting.

A number of months ago I had a cuben shelter to play with for a few weeks. My memory is that it did not mist when hit by the hose… but I am not 100% sure I am remembering this clearly.

–mark

[David Ure]

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[Mark Verber]

I am 99% sure the superfly was made from Spinntex .97

[Oliver Budack]

I experienced with my "Noah Lamport Silnylon" also the misting effect. Good noticeable under a tree when really big waterdrops are falling down. You see how the waterdrop is getting pressed through the grid of Nylon fibres.

If you have condensation on the inside it could be even worse. But then wind would also be a problem because no tent/tarp is that stable/stiff that the fabric does not wave/flutter.

Cuben does not mist. It is not woven. On both sides is a layer of polyester which is waterproof.

Oliver

[Lynn Tramper]

Miguel, if I were expecting a torrential wet and/or windy trip, the Nallo2 would definitely be the tent I would take. Aside from having a more water resistant fly, the inner material sheds any water that does condense or get knocked off in wind. So you pretty much stay dry even if the inside of the fly is saturated. The Nallo is a bit on the short side though, so you have to be careful about the foot of your sleeping bag pressing against the end wall and wetting out. Ventilation is lacking too, so condensation is a big problem if you use fly-only camping.

I don't tarp. The biting midges we have here make it inconceivable for me to want to even try. Solo I would carry a tarptent plus bivy, or more recently take the Refuge-X.

I think the best way to test the water penetration versus condensation question is to do the hose test in parallel with a truly waterproof material such as a polythene bag or tarp. If the tarp starts to 'mist' but the polythene doesn't (or whatever bombproof fabric used), then the silnylon is leaking. If they both show 'misting' then it is a condensation issue.

[stephen wark]

Personally, I love my ahwhanee…fibraplex drops it into the 4's, and solid as a rock. OK its heavy, but divided by 2, its doable. As a solo tripper, I use the Bibker Bipod – still rocks and light. Me likes my comfort…

[Ashley Brown]

Miguel,

I was interested in this and came across a thread on BPL from a couple of years ago about it. I'll quote Jim Wood from that thread on his solution to the problem (also suggested by a couple of posters further up this thread). Same treatment as for silnylon tent floors but more dilute (lighter). Jim reckons it won't add much weight, and if you only put if over the "main" parts of the roof it will be even lighter. I'd rather add an ounce or two to my favourite shelter than to have to replace it altogether!

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Jim Wood:

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.

---

[Ashley Brown]

BTW, I would be very interested to hear if anyone has tried this and how well it has worked?!

[dan mchale]

Much of the silnylon on the market is not waterproof. Some actually holds water and some leaks readily. You have to test is by hanging 1/2 quart of it to see if it leaks. The good stuff does not drip through.

[Frank Ramos]

There seems to be huge differences in the quality of silnylons, based on my experience making my own tarps.

Personally, I fail to see what all the hullabaloo is about a little misting or condensation. If you are spending a lot of time in wet environments, much of your gear is going to get wet, sooner or later, and you have to prepare for this. In particular, if a dense fog drifts up from a valley and starts to cool as it rises, then it will become supersaturated with moisture and it will dampen everything in sight. And that is true even for the finest 2-layer tents, since you have to allow air and thus fog in to avoid suffocation.

Certainly I don't like it when rain blows in under the edges of my tarp, or there is heavy condensation or there is misting through the silnylon (I don't recall this happening even in torrential downpours and I am using silnylon tarps, made from some 1st quality silnylon though I forget the source). However, liquid moisture means temperatures above freezing, which is quite warm as long as there is no wind. Small amounts of liquid moisture that get onto your sleeping gear will thus soon evaporate due to body heat with little risk of hypothermia. There are far bigger problems that I am concerned about, such as how to cope if my tarp should ever blow away in a sudden gust because the ground won't hold my stakes, or I injure myself and can't pitch my tarp correctly, etc, etc.

Incidentally, I use a synthetic quilt now rather than down, precisely because I am often in wet climates where everything gets damp regardless of how the tarp holds up against rain (also, torrential downpours, because they cleanse the atmosphere of moisture, are usually easier to deal with than nonstop drizzle and fog), but that is not because I am worried about the down failing due to small amounts of moisture (at least when temps are above freezing). Rather it is because of mildew. Down that is constantly damp tends to mildew much more readily than Polarguard.

Has anyone estimated exactly how much moisture is misting in though these silnylon tents/tarps? Are we talking liters or milliliters? 100 milliters, if finely sprayed over a quilt, looks like a huge amount of water, but it only takes about 60 Kcalories to evaporate that much water (starting from freezing), which isn't much over the course of 8 hours sleep.

[Jim Wood]

Since I've been quoted here a couple of times, I thought I'd weigh in.

Having designed, built and used many silnylon shelters over the years, it's my opinion that the degree to which misting occurs with standard weight (1.3oz) silnylon is partly a function of the fabric's age and UV exposure history and but mostly related to how well the silicone coating is applied during the manufacturing process.

When new, some of the fabric samples I've used seemed to resist misting pretty well, while others have been horrible. Silnylon is one of those products that's largely unbranded, so you never really know what you're getting unless you buy products from companies that control the quality of their fabrics very carefully.

The good news, at least in my experience, is that the treatment discussed in my article and quoted in Ashley Brown's post really does solve the problem, but with one caveat (see below).

About a year and a half ago, I hiked a portion of the AT and was subjected to several days of drenching rains. I was using a new tent prototype made from silnylon purchased from Outdoor Wilderness Fabrics (I've used silnylon from at least 6 or 7 sources for my projects).

The misting was awful in hard rains and my gear got quite wet. What I experienced was most certainly not condensation being knocked loose from the underside of the canopy, but instead, micro rain droplets that were being forced through the fabric.

By the way, if you're ever in the same situation yourself, you can test the phenomenon simply. First wipe a section of your shelter canopy with a dry cloth to make sure there's no condensation present, then hold a mirror near the fabric and watch the micro drops quickly accumulate on the shiny surface.

Likewise, if you have any doubt that silnylon leaks under minimal pressure, check out some of the photos in another of my articles.

Anyway, after returning from that trek, I coated the entire underside of the shelter with a 1:5 mix (silicone to mineral spirits) and the problem was solved. I've since tested the shelter in torrential rains for extended periods and there has been no misting whatsoever.

And now the caveat. With one of the silnylon samples I used on another project, the silicone impregnation was applied so lightly that the treatment coating wouldn't stick very well. With this experience, I learned that not all silnylons are of equal quality, so YMMV. I should note, however, that with all of the other samples I've used, the treatment bonds very well.

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