Best way to revive DWR?

[Stumphges]

Roger, is spraying silnylon nearly as effective as painting on a silicone/mineral spirits mix? Meaning, will it improve hydrostatic head?

BTW, how do you feel about applying silicone spray or painted mix to the newer silicone/pu mixed or hybrid coatings (not the inner PU, outer silicone) that have become popular recently?

[Roger Caffin]

is spraying silnylon nearly as effective as painting on a silicone/mineral spirits mix? Meaning, will it improve hydrostatic head?
Tricky Q.
Putting silicone spray onto the silnylon fly of my tents helps shed the water. I remain unconvinced that even the old fly material has lost that much HH. I have never seen it leak. I have seen it retain some surface water after heavy rain, so the tent is heavier when packed. I have seen condensation form on the inside under some conditions, but this is NOT rain forcing its way through the fabric. I think the latter is a myth.

I would not try putting silicone spray on a PU surface, and i would not try painting diluted silicone onto PU either. I think it would come off quickly.

On the other hand, I do like some of the latest silicone/PU fabrics: I think they have a real future.

Incidentally, if you want a high HH, do NOT use a ripstop fabric. All ripstop fabrics I have tested leak quickly at the ripstop threads, where the between-thread gaps are larger. I have not found the ripstop fabrics to be any stronger than the plain weaves: I think it is a marketing myth. Yes, I did some testing.

Cheers

[James Marco]

As part of a “lube” kit, I picked up some silicone impregnated wax for zippers. I noticed that the area around the zipper did indeed bead up easier and got some spray silicone for the whole tent (this was around 30-40 years ago.) The tent was an older, plain weave “pup” tent I used for my wife and I. We got a major rain fall and got soaked. It did not help against the heavy rain. I researched a couple things to rejuvenate it, but made a tarp for over the tent out of the new UL silnylon (1.6oz/yd.) Well where I had attached the poles, it leaked after four or 5 years. The fabric was very stretched in this area…indeed, you could catch pinpoints of sunlight comming through in several places. I used mineral spirits/caulk in a rather heavy slury…it didn’t leak again. Actually, It is stashed in my gear storeroom. While it does help with condensation, dew, light mists, it could not handle the impacts from larger rain drops.

As far as coating PU, about three years ago my winter tent (retired to car camping) started leaking from the floor. This was an old Exped Sirius and was noted for having a dry floor even set-up in some of the mud-puddles they call campsites. The tape was peeling off in three places places. Not bad but wrinkled and “whiteish.”  I had nothing to loose since the tent body was getting weak, anyway.  I applied mineral spirits and silicone caulk to it. It flowed into the loose seams and the floor stopped leaking… I would note that I used a fairly thin 20:1 mix. Having used it maybe 20-30 times in the past three years, it still has not come off the floor, though I expected it to..

I also did the fly, but this was not leaking. But, the fabric was fairly weak and had several patches on it…from what I cannot say, squirrels, mice climbing on it, something…little slits.  (Like tension splits but much shorter, perhaps 4-6 “squares” long.) Note that these were between the rip-stop squares, not past them. So yes, the grid of heavier threads *does* do something, at least as the fabric ages. I would opt for gridded rip stop only for the trade off in weight and durability. Though if it was all the heavier thread of the gridstop it would likely be much stronger (and heavier.)

[Stumphges]

Roger, James, thanks for your thoughts. Richard Nisley’s testing has shown that the hydrostatic head of fly fabrics rapidly degrades with use. As Marco points out, with silnylon this has not been an intractable problem for those willing to paint some diluted silicone onto the fabric. But what about the new nylons coated with mixtures of silicone and polyurethane? (Not talking about PU inner side, siliconized outer side)

My understanding is that mixed coatings of silicone and polyurethane (PU) came on the scene when the solvent emissions of old-school silicone coatings were targeted by environmental regulators and it was found that a mixed coating produced fewer emissions. My concern is how amenable these mixed coatings are to aftermarket treatment with the old diluted silicone mixtures. For example, RBTR’s 1.1 oz silpoly, coated with silicone/PU mixture on both sides, starts life at 1500mm HH but degrades to ~500 mm after aging.

Having read reports on this forum that silicone adhesives (Silnet, Permatex) do not work well enough on these coatings to solidly bond fabric reinforcements, I’m concerned that a “refresher” coating of diluted silicone will not adhere permanently. This would greatly reduce the value of this class of fabrics, as they would be essentially disposable after 6 weeks of wet flexed wear and tear. Does anyone have information that would assuage this concern?

At this point, were I making a shelter, I would be inclined to pay more for a 100% silicone-coated product, knowing that I could refresh the coating when it begins to degrade.

Roger, with regards to your impression that HH might not be a (significant) factor in the realworld, I have an aged silnylon fly that leaks around 600 mm. This was a high-value item from a solid manufacturer, and I presume the fabric supported a much higher water column when new.  I would have a hard time trusting my life to this fly in severe realworld conditions, given that I would never consider 600 mm good enough for personal rain gear. Granted, the inner tent might save me if and when the fly leaked, but I don’t think I’d want to chance it. I would rather re-coat with diluted silicone to get above 1500 mm.

On the other hand, you’ve made a lot of tents and have much greater field and lab experience than I. Would you trust this fly?

[Roger Caffin]

As I said, tricky Qs.

I have not found that the silnylon I have been using for my tents for many years has lost all that much HH in the fly. Different coatings, different behaviours. (This we DO know.)

I did find once in France that the groundsheet of my blue tent did leak very slightly when I knelt on it in flowing water, but the tent was many years old by then, and groundsheets get a rough life! At the next town I coated the groundsheet with a very thin layer of something like Permatex flowable window sealant and that has solved the problem for the next 5+ years. It managed to bond with the existing silicone polymer on the fabric. I can’t remember what the name of the stuff was – it was Italian and we bought it at the nearest hardware store.

Yes, the EPA did object to the emissions from the early coating process, but the result was simply that the coating process moved to Asia. I think the sil/PU process came some years later, AFTER that and not as a result. In addition, do not mix up older conventional PU coatings with TPU coatings: they are very different. The older PU coatings would absorb water (hydrolyse) and start to degrade: they went sticky. This was an irreversible degradation. TPU, or thermoplastic PU, is quite different and does not hydrolyse.

Now, something you may not know: the silicone coating on a fabric is porous. It will let water through under pressure. This is not a ‘failure’ of the coating: it is inherent in the silicone polymer. The modern TPU coating is not porous in comparison. I have pressure-tested a si/TPU coated fabric and found really different results, depending on which face was to the water. When the Si face was the wet one, I could SEE the water slowly getting into the fibres through the Si coating. This did not happen with the TPU side to the water.

I don’t think this happened with the original Si coatings either. They had enough solvent in them that the threads were fully wet out by the silicone. But PU and TPU coatings seem to sit ON the surface and not go into the fibres.

Would I trust the fly with an HH of 600 mm? I don’t think I would TRUST it, but I might use it sometimes. The requirements for a tent fly are very different from the requirements for rain gear: rain gear can experience much higher pressures because it is up against something hard. Most likely I would either spray it with several coatings of silicone spray, allowing 24 hr drying between each coating, or maybe treat it with a very dilute solution of silicone sealant.

I would use silicone adhesive/sealant from a squeeze tube for this, NOT the caulking compound you get in large cartridges. The latter is NOT suited ime.

HTH
Cheers

[Jerry Adams]

I have a 2.5 layer eVent jacket that started leaking

I tried reviving the DWR – wash, and repellent – I think I used Atsko

It didn’t help.  The membrane started delaminating, that is it became discolored.  Especially on the hood and shoulders.  Other people have reported this too.

If that’s your problem then reviving DWR won’t make much difference.

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