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I have a 50-liter backpack which I used very little and that afterwards was kept stored for more than 10 years.

Today I noticed that some parts inside, I think the waterproof coating, has become sticky. This is apparently a common problem (read here and here) due to the breaking down of the urethane coating.

What one can do to remove the stickiness? From what I've read, one should avoid machine washing, and some people solved the problem by rubbing the inside with talc powder. Are there any other solutions?

EDIT: similar question: What is this brown dust/powder inside my old pack? However, in my case the coating looks perfect and is not delaminating; it's just sticky at the touch.

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    Sounds like the plastic is de-laminating. Not much you can do but try and protect it or buy a new one. Make sure you protect it from things like UV light as much as possible as this can increase the de-lamination process.
    – user2766
    Jan 11, 2018 at 13:31

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Solution: Use Ethyl / Denatured Alcohol to dissolve it off. I've used this solution on two bags now and it had worked amazingly.

Bag 1 - Thermarest stuff sack: It was so sticky I had to peel it apart. I turned the bag inside out and put it in a jar with rubbing alcohol 91%, let it soak for about 24hrs then pulled it out of the jar & used a scrub brush on the sticky part. The old coating either went into solution or balled up and came off.

After a second soak/scrub, I threw it in the wash on hot/quick with laundry powder to help wash away the rest of the solution. After it air died, it was completely tack & odor-free.

Bag 2 - older Dana Design pack: A larger (60L) pack with many facets, with the same issue. First, I took off as many of the straps, foam & stiffeners as I could. I put it in a trash bag, then put that in a bin of water. This way, when I poured Denatured Alcohol into the trash bag with my pack inside, the pack would get soaked/saturated without needing 3 gallons of alcohol. The snap lid of the bin also helped hold the pack down, preventing it from floating on the surface of the water.

After it'd soaked for 24hrs, I put on rubber gloves & pulled the bag out for agitation. I used the lid of my bin as a tray outside, to capture as much of the alcohol as possible, so I could pour it back in the trash bag for round 2. I scrubbed the pieces of fabric against each other or used a stiff brush. When I was satisfied, I hosed it off, threw it in the wash & air died. It's completely tack free.

I opted for the denatured over rubbing alcohol because it's mostly ethanol (renewable). As a solvent they worked about the same. I didn't try diluting them. Hope this helps!

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  • Thank you, I'm going to use this approach to rescue my 25 year old Dana Design pack as well.
    – Charlie Weems
    May 16, 2021 at 18:12
  • Unfortunately this didn't work out for my bag. It's still sticky.
    – Ouroboros
    Jun 26, 2021 at 13:27
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I had this problem with a favorite fanny pack (L.L. Bean) a few years ago. I turned the pack inside out and used a stiff brush on it to get it all out. I even tried a wire brush for tough spots. But, you have to be careful not to damage the pack itself. As a result, I now try to find/buy packs that don't have this coating. There are some with a plastic liner. Or, I get an unlined pack and use zip-lock bags or plastic containers. Using the bags and containers actually keeps things more organized.

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  • My experience is that if you heavily use the pack, the urethane coating just wears away and the stickiness/flaking never becomes a problem or is at least unnoticeable. The duffle bags that get used about once a year do show the problem, but the day-pack that I use every week since almost 10 years ago hasn't.
    – Gabriel
    Sep 13, 2018 at 18:10
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I have temporarily solved the problem by rubbing the sticky part with talc. But this protection leaves a bit of talc around, and must be repeated every few days. Luckily I don't use the backpack for long trips.

This is far from being the best solution, but at least allows me to use the backpack (I don't want to throw it away).

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  • Another not-really-fix solution is to line the backpack with a trashbag. (Even re-waterproofs the bag!)
    – adeadhead
    Sep 21, 2020 at 15:34
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I had a Deuter bagpack which had similar problem. I kept the bag in hot sun (covered in old cloth so that no fading happens) for few days and then washed it with detergent with a nice scrub on the sticky parts. Now its like new...

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I have had this problem with several packs. One solution that has worked for me is to spray the insides with VALSPAR Premium Finish-Satin (in a very well ventilated area).

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I had this same issue with a twenty-year-old CamelBak which hadn’t seen heavy outdoor use. I guess the coating just ages out over time and becomes sticky. I tried scrubbing it out with an old toothbrush, and then noticed that the silicone portion of the bristles was doing most of the work. Turned it around to use the mostly silicone toothbrush handle, and the sticky stuff started coming off in rolls. (I expect a silicone barbecue glove would have made this go even faster.) I was able to get most of it off and vacuumed out of the bag interior, but the surface if the fabric was still slightly tacky to the touch. I found that a 70% isopropyl alcohol pad (first-aid type) was able to remove the last of the tackiness. I tried using 100% ethanol and it seemed to smear the sticky stuff around.

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