Restoring a shelter with a degraded PU coating

[Roger Caffin]

I am biased of course. In my experience the older PU coating is obsolete today, and should be discarded. That applies especially to any of the water-based ones.

Mind you, the solvent-based thick Shoe-Goo and similar can be good stuff, but I would not try to use them on fabric. Sad to say, when a PU-coated tent gets sticky or starts to leak, imho that is end-of-life for the fabric.

You might like to note that whereas PU coatings reduce the tear strength of a fabric, the silicone coatings actually increase the strength.

Cheers

[Nick Gatel]

It is water-based. Get it wet for too long (12 hrs?) and it will revert to that milky-white goo as you called it. It may even then wash off.

Are you sure? Yeah, I know you are a textile scientist and I’m just a layman.

It is very common to use water-based brush-on products (AquaDefense or Redgard brands) for water proofing shower pans, walls and floors in construction. I used these products when I remodeled our bathrooms a few years ago. Of course these waterproof barriers are static and not subject to the folding/rolling up of tents.

How does exterior paint stay waterproof, since most are now water-based?

From Wikipedia on latex paint:

The term “latex” in the context of paint in the United States simply means an aqueous dispersion; latexrubber from the rubber tree is not an ingredient. These dispersions are prepared by emulsion polymerization. Such paints cure by a process called coalescence where first the water, and then the trace, or coalescing, solvent, evaporate and draw together and soften the binder particles and fuse them together into irreversibly bound networked structures, so that the paint cannot redissolve in the solvent/water that originally carried it. [Bold is mine]

https://en.wikipedia.org/wiki/Paint#Binder_.28or_film_former.29

 

So will my treatment last? We’ll find out in a few years. The important thing is, after treatment, I left the shelter standing in my backyard for a couple days where the conditions were very dry and hot, allowing the water to evaporate and the binding particles to fuse together.

 

[Roger Caffin]

That’s a good question, and I will try to explain.

The technical explanation for the absorption of water by some PU coatings is that they ‘hydrolyse’. The PU absorbs the water slowly and the whole structure breaks down, but that can take many hours. To put this in a familiar context, I am sure many will have heard of old tents going sticky after being stored for a long time. That is the same thing: the water in the rolled-up tent is slowly being absorbed.

The trouble is, once this process starts, it does not seem to be reversible. Yes, the PU fabric coating was probably a water-based emulsion when it was put on, but it would appear that there was some sort of chemical change when the coating initially dried out. Further than this I cannot say, as I don’t know. All I can say is that I have never heard of any way to fix the problem in tents, and many have tried.

So how come water-based PU coatings work elsewhere? That’s simple: they are not stored for months while wet. Sure, a shower may get wet – briefly. Then it dries out again. The lack of oxygen inside a rolled-up tent might have something to do with it, but that is just a hopeful guess.

Anyone can test this idea themselves. Get some white wood glue of the PU sort (NOT epoxy, NOT solvent-based, just PU). Glue some bit of timber together and let the joints dry. Then after a week or so, wet it all down and bag it up in a couple of layers of plastic film or bag to keep it wet for a few days. After a while you will see the glue starting to go white, and then the joints will fail. Same thing I believe.

However, this old sort of PU coating has been replaced with a thermoplastic PU coating, called ‘TPU’. This stuff is totally different and does work and does last. Figures that the coating suppliers would try to improve.

Cheers

[Elliott Wolin]

I’ve had luck removing sticky PU coatings by simply laundering them multiple times in a strong detergent.  I use a standard top-loading washer.

[Roger Caffin]

Hi Elliott

Yes, I know about that approach. I can only assume that the detergent is helping to break up the PU mess and float it away. I believe that it works, although how many wash cycles will be needed is unknown and may vary :)

The question which obviously follows it how to reproof the tent. Using a simple commercially available PU coating product (several on the market) is to my mind just silly. That is simply repeating or reinstalling the problem, and you won’t be doing it as well as the original.

I am not aware of any good reliable processes for recoating a tent. There are all sorts of ideas, like diluting silicone sealant and painting it on, but the reliability and the weight gain are both unknown. Silicone is great for seam-sealing silnylon and silpoly as you can get it into the threads.

Which is why I suggest that the user might be better off swallowing his losses and buying a new tent. (mumble mumble mumble)

Cheers

[Elliott Wolin]

Roger’s advice is probably sound:

“Which is why I suggest that the user might be better off swallowing his losses and buying a new tent. (mumble mumble mumble)”

Alas, this is really difficult for a guy who still has every camping item he ever bought that didn’t disintegrate.  Indeed I have four or more generations of equipment going back to the early 1970s, and there’s a lot of it since for some of the generations I had to outfit five people!

Maybe I need to enroll in a 12-step program?

Anyway, I’m mainly interested in refurbishing car-camping or front-country equipment, for the backcountry I use pretty modern stuff (mainly MYOG silnylon tarps).

I’m currently looking to refurbish a six-person, four-person, and two three-person dome tents, along with my truly ancient REI Crestline A-frame tent (this mainly for nostalgic reasons).  One of the three-person tents is a bombproof SD Dome tent, still suitable for winter if I ever go camping in winter again.

My wife is pushing for the 12-step program…

 

 

 

 

[Jim W.]

Nick- Long time no see!

I need to recoat the fly on our “new” circa 2018 PU coated REI Half-dome before a bike trip next month.

Some questions:

How has your coating held up? http://popupbackpacker.com/resurrection-my-chouinard-pyramid-rises-from-the-dead/

Do you recall the coverage?

what are your thoughts on coating the outside if not removing the existing coating?

 

Jim in Long Beach

[Nick Gatel]

Hi Jim!

Gosh, it’s been around 15 years ago that our families did that camping trip in Joshua Tree.

I have used the shelter several times since the re-coating. The last time was a couple months ago. Still water proof. Also, since I store it in my garage, which can reach over 120° F in summer, I am pleased that there is no stickiness, no smell, and no de-lamination at all.

I followed the directions of the product exactly. When applying you can tell if too much is used, as I explained on my blog post. I recommend following the directions and apply to the inside.

Dan McHale uses the product a lot, and for packs he recommends two coats. Here’s a link:

http://www.mchalepacks.com/ultralight/Detail%20Hi%20Rez%20Pages/Pack%20Damage%20Page.htm

[Jerry Adams]

I got some gear aid tent fabric sealant

I turned my pack inside out and stuffed it with blanket

I washed off the fabric a little, not dirty, maybe some salt

With the sponge top, it was difficult to get a lot of sealant out.  The sponge is only 1 inch in diameter.  I can’t imagine sealing an entire tent – it would take hours.  And be difficult to carefully get all spots without missing any.

I think maybe it would be better to get one of those foam paintbrushes.  Port some of the tent fabric sealant in a tray.  Dip the brush into the tray, then brush the tent.

I only did the back and bottom of my pack, which is a small area, so I think I did it good enough with the supplied foam top.  I’ll give it a second coat (as McHale recommends).

[Jerry Adams]

Dan said the tube is like a squeeze tube.

Okay, when doing the second coat I tried squeezing to get more liquid out.  Oops!… the foam cap popped off and liquid splashed out over the pack.

Not to worry.  Used a paper towel to spread it around pretty evenly and wipe up any spilled.  This might actually be a better way to spread it out – pour some on and then spread it out.

Maybe within a month I’ll be able to try it and see if it’s now waterproof.  My main problem was sweat got through and got the bottom of the contents wet.  My next trip will be hot and I’ll get very sweaty so it’ll be a good test.

[Jerry Adams]

It dried within a couple hours but I let it dry for a couple days.  It wasn’t at all sticky.  I couldn’t even tell the places I applied it (back and bottom) compared to the places I didn’t apply it.

With Seam Grip, I have to let it dry for days and even then it’s still sticky.  When I accidentally let two places touch, I couldn’t get them apart.  The seam grip came off the fabric on one side.  You have to put something like talc on the surface to prevent this.  The Tent Fabric Sealant doesn’t do that at all.

I’ll be interested to see if it’s actually waterproof.

[Jim W.]

Nick and Jerry,

Thanks for the replies. I bought three bottles which should be plenty for the fly and the tent floor if I decide to do that.

I soaked the rain fly in a strong soapy solution for several days, then ran it through our front loading washer three times. I guess the coating wasn’t as completely failed as I thought because it’s mostly still there. I’m thinking I will just coat the outside so that the new coating can lock into the fibers. I’m guessing that the Coating is not very UV resistant so that’s a concern.

 

[Jerry Adams]

If you’re setting a tent up at a basecamp over the summer, UV resistance would be important

If you’re hiking during the day and setting up your tent in late afternoon and taking it down in the morning, UV resistance is not very important

I put a piece of silnylon up in the sun all summer.   It was then faded.  It still had most of it’s strength but was a little easier to rip.

[Jerry Adams]

after several hot trips and one rainy trip, my pack is pretty waterproof after applying gear aid tent fabric sealant

my last trip was especially sweaty and a little sweat got through the fabric but not enough to matter, my polycro was against the fabric which had a bit of wetness, but nothing dripping down to the bottom of the pack like it used to

maybe I’ll have to re-apply every 6 months or a year

this has been a “white whale” for me – trying to get my pack water-proof.  This is pretty close – 210 D Robic from RSBTR + Gear Aid tent fabric sealant water based

[Author]

Posts