GEAR AIDSeam Grip TF Tent Fabric Sealer for Waterproofing and Restoring Polyurethane Coating (PU) on Nylon Tent Floors, Rainflies and Tarps, Treats up to 85 sq. ft, Clear, 4 fl oz, 1 Pack

This is a very good solution for repairing worn out PU coating on the inside of backpacks.Be sure to remove the remnants of the old PU coating completely (a time consuming process) and then apply this sealer and it works great. I used Isopropyl alcohol in a spray bottle to help remove the old coating.This sealant also restores some of the structure to the fabric so it's less floppy.One 4 oz container covered the all interior compartments and pockets of a 36 liter backpack with some left over for future use.

This was my first time using this tent sealant, and like other reviewers have stated, 4 oz is not as much as you think it is.I have an older REI Half Dome 2 Plus tent that needed the whole rainfly redone. I bought two bottles of this stuff, thinking that would be enough, but I needed three bottles (another is on it's way). I still need to do about 3 feet by 4 feet section at the bottom of one of the tent ends. I know now that when I first started applying it, I put on too much and learned as I went, but next time I will probably be able to do this size tent with two bottles.I think the applicator that comes on the bottle is trash for larger jobs, but would be okay for small patch jobs needing a touch-up. It's not meant to do a whole tent floor or rainfly. Most of the videos I saw of how to apply it (the REI video in particular on how to waterproof a tent) show this guy just applying it to a small area of flaky residue. I took the foam tip applicator off (its not threaded or anything, it just slides out) and got an old plastic tupperware bowl. I dumped a little bit in after shaking and then got an angle tipped foam brush with wooden handle (these are mostly for painting and arts and crafts, but it worked great for what I needed).I then setup the tent and the rainfly inside out (it's for applying on the underside of the tent rainfly) and brushed it on the entire area, keeping a wet edge (where I could see where I had previously applied the product). Over time, I used my fingers to push the foam brush against the fabric even more and more tent sealant would seep out of the foam as I went, again, keeping that wet edge.I then let it dry like the instructions for 24 hours. It leaves a clear, non-viewable layer of polyurethane on the underside of the tent rainfly. I can feel the difference in the tent fabric when I run my fingers on it. It's hard to describe the difference, but the untreated area feels soft to the touch, like running your fingers across a newspaper, whereas the treated side feels slightly rougher, like the side of a cardboard Amazon box.I'm so happy to breathe new life again into my old gear. I haven't tried a rain test on it yet (still waiting on the 3rd bottle to finish it, but I think my tent will do great now.Just buy an extra bottle than what you think. You can use the extra sealant to do the tent floor to prevent a slipping sleep pad.

I was extremely hesitant to buy this, based on the multitude of reviews that claimed it was very difficult to apply, and Gear Aid's coverage claims are a lie. But I figured I'd give it a try before buying a new tent.Gear aid is correct. It covers an incredible amount of surface area. It is easy to apply. I used a single bottle to refresh an entire tent. I did the floor in about 40 minutes. I did the rain fly of a tent in about an hour. There's still a little bit left in the bottle.The best strategy is to use short 4-6 inch strokes, pushing the bottle away from you. Just keep moving over inch by inch, and cover the area, then back up and do the same thing again. You'll see the surface gets slightly damp that you've treated. It starts to dry relatively quickly, and sometimes can be hard to see where it's already been treated because of that.I haven't yet sprayed down the tent to see efficacy, but the old coating was still mostly effective so that won't be definitive. And from the small amount of liquid on my fingers, which dried into a polyurethane coating, seems pretty clear it works.Buy it, treat your gear, and enjoy. It's slightly tedious, but not hard. All you're doing is getting the surface slightly damp. You have to make sure to keep pressing the bottle down and squeezing a little bit during your strokes. Occasionally, stop, press down hard, and squeeze, to resaturate the sponge fully.Easy, not super time consuming, and a very inexpensive way to rehab a tent.You're painting on an extremely thin layer which closes the pores of the fabric and makes it waterproof. You are not putting down a multi-millimeter layer of polyurethane. Those people who claim it uses seven bottles, or four bottles, and that you need a paint brush, don't understand how DWR works. Think about the last waterproof jacket you bought, or your tent when it was brand new - it did not have a multi-millimeter thick layer of polyurethane on it. It looked and felt like fabric, and invisibly had a DWR coating on it. That's what you're restoring. That's what this does. And the sponge applicator allows out exactly the right amount of liquid.

I used this last year and no leaks.

My PU coating had become sticky. I washed my tent and rainfly several times in concentrated laundry detergent, until most of the coating had pilled off (coming off as small round lumps, or pills). I let it soak for several hours in a tub of concentrated laundry detergent and water and agitated. I didn't measure, but probably had 4 times the normal amount of detergent. Then I scrubbed it with a brush to remove residual, finally washing in Woolite and then twice in just water. I let it dry thoroughly. I tried various ways to apply this product. What worked best for me was to pour it into a measuring cup, then use the applicator, dipping it into the cup to wet it, then making quick back and forth motions on small areas at a time. It absorbs into the fabric, so even though it doesn't go on evenly, it smooths itself out so long as I got the application fairly uniform. Dipping the applicator worked very well, and the applicator slides nicely across the fabric, minimizing the bunching of the fabric, and it actually goes on fairly fast even though the applicator is small. The final finish looks great, though the fabric is a little stiff. I ended up using about 3 bottles (12 oz) for a Sierra Design two person tent floor and rain fly.