A Tip For Those With Misting Sil Tarps

[vitamaltz]

I know I'm not alone in experiencing some misting under my tarp in a downpour. It's not really leaking; it's just very small droplets falling and tickling my nose just enough to prevent a deep sleep.

My main tarp is a DIY 10x11 with olive sil from OWF. I made it two or three years ago. It gets something like 100 days of use a year, and often gets stuffed into the pack soaking wet. I've noticed that this spring the misting was significantly worse, probably due to wear and tear on the fabric and the occasional sunshine beating down on the tarp (UV and silicone don't like each other). A few weeks ago, I decided to give the make-your-own-sil thing a try. I mixed up caulk and mineral spirits, taped the tarp to the driveway, and went to town with a squeegee. I really tried to keep the application thin, especially since I was trying to reseal old sil, not create sil from regular ripstop.

I started camping Thursday night last week and it's rained on me all five nights since. The first four nights, I had the newly applied silicone facing up, toward the clouds. I was pretty disappointed to still notice misting. Last night, I tried flipping the tarp over, so the newly-coated side faced the hammock. Not a droplet on my face! I think I know why. I don't believe a misting tarp is actually leaking straight through. When I had the newly-sealed side facing up, the fabric underneath was still being wetted out by water vapor circulating under the tarp. Shine your light into the air under your tarp on a rainy night and you'll see what I mean; there is a lot of water suspended in the air. I think the degraded sil will soak up some of that moisture, which will then be propelled toward the hammocker by the percussive force of raindrops on the other side of the tarp. When I placed the sealed side down, the fabric closest to me couldn't hold much moisture anymore and the misting stopped.

Geez, that's a long-winded analysis, but if anyone else is being dogged by Chinese water torture, they may want to give it a try.

[SteveToTheO]

Do you know about what portions you used for the mixture? Im thinking about making a cat tarp soon and everything that Ive read has pretty much done it by feel.

Steve-O

[WV]

Useful observation. I've touched up older sil tarps by spraying "Atsko Silicone Water-Guard by Sno-Seal", but I usually sprayed both sides, which uses a lot of silicone. Next time I need to refresh a tarp I'll try just spraying the under side. Thanks.

[vitamaltz]

I did it at 5:1. I think others have done 4:1. 5:1 (by weight) is approximately half of a big can of mineral spirits and one tube of caulk.

I think coating both sides may make the tarp less soggy when I stuff it away, but it wasn't worth the weight gain for me.

[psyculman]

vita,

An interesting observation, but, my material is sprayed on both sides, and, it did seep in a torrential down pour, meaning pretty big drops of rain hitting it, not ambient humidity. I can put it up to my mouth, and still pull air through it. I gave the material several coats of the DIY silicon/mineral spirits mix,.... sprayed on with an industrial spray system. Maybe need to give it some more, but, do not want it to be "rubbery". I have not thought the tarp to be useful since. Someone else may have experience with this.

[rip waverly]

i've not noticed misting so much at all with spinnUL.

i'll keep an eye on my new jrb 10x11 though-- thanks for the tip~!!!

[vitamaltz]

i've not noticed misting so much at all with spinnUL.

One of these days I'm going to verify that for myself

Psyculman, if you hold a small section of the tarp in your fist and make a bag or bladder out of it and then fill it with a few cups of water will it leak through?

[psyculman]

vita,

Yes, a few drips form immediately, and with a little pressure, it flows all over the place. Maybe another coat or two of DIY spray?

[vitamaltz]

I don't know. I wonder if it's the spray application that could be the problem? I had some other fabric that was advertised as sil but leaked like a sieve with that test. I did the caulk and spirits thing with a squeegee on that stuff and now can't get a drop to pass through under the sink. I'm sure your spraying is really even, but if that's somehow causing small bubbles to form on the surface, that might be a problem...

[exup]

Thanks for the report. How long would you say it was before your tarp started misting? Or how many nights? I have heard somewhere around hundreds, though I don't know if that's the truth. Hopefully if that's the case, with the minimal trips I get it'll take 20 years haha.