A couple of years ago I salvaged a bunch of nylon tents and tarps that were going in a dumpster because they were not selling at the scout shop garage sale. Some of this stuff was 20 to 30 years old and had been in storage at the scout shop for decades and they were clearing space. I showed up an hour before they closed up on the last day of the “Garage Sale”, and I picked out 2 tarps and 1 tent. But the fellow running the sale knew me and told me, grab as much of the nylon stuff as you want because it’s all going in the dumpster. So I sorted through and found another half dozen old green dining fly’s, 5 or 6 old tends and two what I thought were rainfly’s but turned out to be Kelty Noah’s tarp diamond flys. I was excited. Until I started using it and most of it was so old it was not even roughly water resistant. (About as waterproof as a coffee filter). A couple of the tents turned out to be in decent shape, but the 6 tarps and the 2 Kelty’s were only good for sunshades.
I’ve meant to try out the re-silicone-waterproofing process on these but just never got around to it. Well, I finally decided to try it. Picked up a gallon of odorless mineral spirits $12.49, a 5-gallon pail $2.89 and a 12 oz tube of clear silicon caulk $3.99.
I’ve read of this technique with people using a 10 to 1 mixture of spirits and silicon up to a 15 to 1 mixture. The 15 to 1 is the “Weakest” lowest mixture recommended to get full coverage. 10 to 1 is the maximum. (too much and you get lots of silicon excess on the tarp which doesn’t hurt it, but can be a little streaky and may make the tarp stick to itself if it gets hot in a car trunk or something. As it turns out the gallon is a 126 oz of mineral spirits, and the 12 oz tube so I decided to not bother measuring it. This ends up about a 10.5 to 1 ratio. So a little on the heavy side as you can tell by the small amount of streaking I got on the dining fly.
I observed a fellow use a paint stirring bit in a drill to mix the silicone into the spirits, making the spirits opaque, almost white before he used it. This left lots of streaks and excess silicone on his tarp. I don’t recommend that, as you need the silicon to dissolve, not just mix. So, I poured half the spirits in the bucked, then squeeze out the entire tube of silicone, then added the other half of the spirits. I just slowly mixed this with a piece of PVC pile for about 6 or 7 minutes by hand until all of the silicone was dissolved. The mixture was still perfectly clear, no white haze or silicone visible. That’s when I knew it was ready.
I estimated I’d be able to do 2 of the dining fly’s and the 2 Kelty Noah’s tarps. I managed to get the two Noah’s and 1 of the dining fly’s. This takes some preparation because you don’t want to drag the nice wet tarps across the dirty ground. So, setup your hanging area first so it’s all ready. Then pull your tarp down and start putting it into the bucket, in the reverse (starting at the bottom furthest from your hanging points). Squeeze the tarp and mix it into the solution until it’s thoroughly saturated on the entire tarp. My tarps are big, the dining fly’s are 10 x 12 and the Noah’s are 12 foot diamonds. It took some effort to get the entire tarp in the bucket and mash it around like your washing laundry. As I pulled it out, I noticed a couple dry spots where it was folded against itself. So I pulled it apart and smashed it down in the mixture again. The Noah’s were like sieves, allowing the liquid to saturate ever inch of them in a minute or two of kneading. I pulled them out of the bucket slowly and squeezed as much of the liquid out as I could. Hung it up and staked two corners to keep it taught.
I proceeded to do the same thing with the dining fly. It turned out to be a bit more difficult because it was still slightly waterproof. Each time I tried pulling it out I found more dry spots. Took me abut 6 or7 minutes of dunking kneading and pulling it out and putting it back in to get it fully saturated. Got it hung up. Because it was more waterproof, it also pulled more puddles of the mixture out of the bucket with it. So, when I hung it up it was much more wet and took longer to dry. I then did the second Kelty, and barely had enough liquid to finish it. (In fact, the bucket was nearly dry by the time I pulled it out. So, all 3 are now hung up. I had read that it’s best not to dry super-fast on hot sunny days as the silicone “Bunches” up in spots. Slow drying should give it a more even coat as the silicone attaches to the fibers. My day turned out to be perfect. Overcast, cool in the mid 60’s with a slight breeze. Took about 2 ½ to 3 hours and the tarps were mostly dry (two corners on the last Kelty were still damp). An hour later they were all completely dry.
The Kelty’s are a very light gray, almost an off white so no silicon was visible anywhere on them. The dining fly is green and there was a little bit of silicone white streaking in a few areas. It’s strictly cosmetic so it doesn’t bother me a bit
I then setup the rainfly and one of the Kelty’s in the yard and had my 11-year-old stand under them while I soaked them with a heavy spray from the garden hose for a full 5 minutes without a single leak!! Not any drop, even at the seams which I sprayed extra hard did not leak a bit. This is a short-term test, so It’s going to have to wait for me to be camping through a nice long overnight storm to get a feel for the longevity.
As an added bonus, this afternoon we got some rain. So I sat outside in the cool weather typing this article up under my now 100% waterproof Kelty Noah’s tarp which the last time I used just poured water though almost every square inch.
I HIGHLY recommend this method of waterproofing. The cost ended up being roughly $6 per tarp. It was an easy job, not as messy as I thought it would be. Soap and water took the spirits and silicone right off my hands and forearms no problem. (My bandage fell off and the small cut on my finger didn’t even burn in the spirits which surprised me). I really wish I had not waited so long, I could have been using these tarps a long time ago.
I have 3 or 4 more of the dining fly’s to waterproof and then I may even hit up one of the older tents and try that.
Good luck and enjoy breathing new life into your tarps and tents and other nylon items.