Why is there mist in my tarp?

**heavyhanger** · 06-15-2021, 17:03

My tarp is a DIY 12x10 made of 1.1 oz nylon fabric that I waterproofed with about 6 cans of spray waterproofing. and then used seem seal on the center (ridgeline) seam. I was laying under it a couple of days ago with my son set up a couple of trees over. A pop up shower started, and in a few minutes I noticed a very fine mist under my tarp. It got so bad that I could not see out of my glasses and my son noticed it and commented on it. It was like the rain was being forced through the fabric under very high pressure?

**mcimes** · 06-15-2021, 18:42

If you used standard nylon and "waterproofed" it yourself, its likely not very waterproof. Backpackinglight tested many fabrics waterproofness and found that light and ultralight fabrics, few met their official standard for very long after they were produced. Even a flaw in a few threads could compromise the waterproofness.

Also, most waterproofing is Silicone or Urethane or both. It fills in the gaps between the individual threads. My guess is a spray on waterproofer does not make a uniform layer and allows water thru.

Last, did you apply DWR (Durable Water Repellent) or a Silicone/Urethane waterproofer? DWR is not waterproofing.
Even if it was Sil/Ure spray, its likely far inferior to industrial stuff.

I would only recommend factory-coated Poly or Nylon fabric. The home made waterproofing is inadequate for anything but light mist.

**OlTrailDog** · 06-15-2021, 19:03

Chili for supper?

**heavyhanger** · 06-15-2021, 20:13

It was silicone waterproofing spray. I just found it odd that in a steady/hard rain, there were no drips, just a mist. I may just replace it with a commercially made one. The $40/$45 I would spend on more spray would take a good bite out of a new one.

**mcimes** · 06-16-2021, 00:22

You can make your own too, just use commercial silnylon from ripstobvytheroll, don't waste your time trying to waterproof non silicone fabrics yourself. Or consider a commercial version, whatever works

**nanok** · 06-16-2021, 02:13

it really sounds like you created a "sieve" of sorts, and the droplets disintegrate on impact into much smaller ones and some make it through. that must be quite beautiful to see (well, okay, not for your purpose i guess, but you must see the beauty in it).

i think indeed the spray is not good for this, might be a good solution for garments and such, but with a tarp, you want to saturate the fabric with the silicone solution, not just spray it. some people "paint it" on, some soak it and then leave it (deployed) to cure for a few days, both methods seem to work fine, i was planning to try soaking myself (i'm not much of a painter).

don't be discouraged, your result might not be perfect, but if you like the tarp you made, it's still worth trying to waterproof it properly, but don't buy any more spray cans, you gotta get serious: bucket, clean wooden stick, and let it swim (it will also be a lot cheaper)

edit: this guy sounds convincing, all i'm saying is i'd give it a try before giving up completely and buying something else. for the price of a can of clear silicone glue and some paint thinner, i think it's worth it (you already did the hard part: designing and making the tarp itself) .

**dscotthep** · 06-16-2021, 11:50

If you want to waterproof your own fabric, check out this thread. It has everything you need to know!

**nanok** · 06-16-2021, 13:30

thank you, that's great. (and i hold you responsible, obviously now i had to read it all). it's just that the nights are so short lately, not enough time for reading :P

**heavyhanger** · 06-16-2021, 19:02

I think, in the hear and now, I am going to relegate this tarp to fair weather duty. We are fair weather outdoors people as it is. We may overnight on an easy trail, if we are already on a camping trip. We travel with a travel trailer so camping for us is a little different. If I am hammocking in bad weather it is on a hunting trip and I will be solo. In that case I can just pick up a hex tarp for just me which will probably be a little lighter in my pack anyway.

**nanok** · 06-18-2021, 03:16

Originally Posted by heavyhanger

I think, in the hear and now, I am going to relegate this tarp to fair weather duty. We are fair weather outdoors people as it is. We may overnight on an easy trail, if we are already on a camping trip. We travel with a travel trailer so camping for us is a little different. If I am hammocking in bad weather it is on a hunting trip and I will be solo. In that case I can just pick up a hex tarp for just me which will probably be a little lighter in my pack anyway.

that is most disappointing.

joking aside, if it's as you say, i'd consider doing something else: you have very lightweight material, and (now) detailed instructions to waterproof it on the cheap. if you're fair weather campers, you'd be better served maybe by having some ponchos, than a big tarp, and this lightweight material is excellent for that. for a big tarp to use for cooking etc space when car/trailer camping, you don't want lightweight materials, you get something sturdy and cheap i would think. you could easily make two or even three 8x5 ponchos out of that thing, and you'd end up with a very nice and useful piece of gear, that also serves as a solo tarp (nice to have on a day hike for instance if you get a sudden t-storm and want to get out of the rain ). i know it's heresy to talk about an 8x5 tarp here on HF, but perhaps it helps give some ideas. i'd put that material to good use, is all i'm saying (but maybe i'm just too stressed about ripstop, over here "dollar ripstop" sounds like a fairytale, if you can get something decent for 6-7bucks it's a bargain, it's often hard to get anything at all, unless ordering online)