Recoat failed DIY Sil attempt?

**Rain Man** · 09-06-2013, 10:09

Originally Posted by gargoyle

For all the monkeying around and added expense of diy sil, I say just buy silnylon and be assured it will work.
While some folks have had limited success, the treatment seems doomed with technical/operator errors.

Agreed, especially for large-scale projects, such as an entire rainfly. Here are my two opinions (worth about two cents only)--

1. commercial sil-nylon isn't merely soaked in a silicone mixture, but it is pressure-rollered into the fabric.

2. even commercial rainflies will get condensation on the bottom side and appear to be leaking, when they really aren't.

Rain Man

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**zooshooter** · 09-06-2013, 11:25

Originally Posted by schaapj

Hi Everyone,

I can't say enough good things on the knowledge sharing that goes on here. It's been the primary source of information that enabled me to build both my hammock and tarp....and also my source of blame for my new hammock and DIY addiction.

I recently took both on their inaugural voyage on a 6 night wilderness trip and while it went so well I'm now a life long hanger. Unfortunately though I did have one small hitch...I found out during a monster storm on day 5 that my DIY Sil tarp is not waterproof. While a large amount of water beaded off the tarp as expected, water also penetrated the fabric all over getting everything underneath wet. Making matters worse, I forgot my back-up poly tarp and I was forced to the ground in my buddy's tent.

The waterproofing method I used was the soak in a bucket method with mineral spirits and silicone as detailed in the "make your own sil" thread. As such, I think the source of the leak may be due to the ratio of mineral spirits to silicone as I think I ended up with a 6:1 ratio when I was targeting 3:1. Possibly adding to the issue, I'm pretty sure the fabric I used was polyester garment liner ($1.00 Walmart fabric of "undetermined origin")...made for an extremely comfortable hammock, but maybe not such a great tarp...not sure?

A couple of questions for those of you who have experience in the "make your own sil" department is:
1. Has anyone had any luck recoating DIY sil when the initial coat was not sufficient? If so, what method did you use to recoat and what ratio mineral spirits to silicone?
2. Would using polyester vs. nylon cause any problems in waterproofing with silicone?

Any additional insight is welcomed as well.

Oh, and for those that are interested, here's my completed DIY setup on a test run on Independance Day at the in-laws.

Attachment 55196

Did you have the tarp hung tight like it would be regularly when you were working on it or did you soak it and then hang it loose to dry? It is important that you string it up after soaking it so that the fabric is under what will be regular operating tension, and then use a sponge to go over the fabric again while it is still wet from the initial soak.

**schaapj** · 09-06-2013, 23:46

You guys rock! Great discussion/suggestions! Sorry for the delayed reply but between work and the honey-do list it's been a busy day.

Originally Posted by Nift

Try hanging it tight and using a sponge to spread the mixture on. Also there is some information out there to make sure that your mixing bucket it very clean or it can cause adhesion problems.

I'll likely either give this or a brush-on technique a try. I was quite diligent in making sure the mixing bucket was clean so I'm pretty sure that wasn't the issue previously...I'll make sure to do this next time as well.

Originally Posted by gargoyle

For all the monkeying around and added expense of diy sil, I say just buy silnylon and be assured it will work.
While some folks have had limited success, the treatment seems doomed with technical/operator errors.

I totally hear you, but I am like most DIYers...it's the "monkeying around" that keeps the additiction going until I finaly hit that brick wall hard enough to realize a different direction is needed (not there quite yet

).

Originally Posted by Klaussinator

Here's what I suspect might be the difference: I used Taslite fabric from WallyWorld since it was cheap and I liked the camp pattern. This material took the SIL mixture well, but I've noticed on my tie-out loops where I used nylon straps, that the SIL coat peeled off the tie-outs within a few weeks. No matter as far as needing to be waterproof, just an interesting observation.

Agreed, the fabric is deffinately a difference (I may have to look for Taslite in the near future) but the observations you had in your process are very similar to mine. The silicone mixture took to my fabric very evenly and completely just as yours did and still looks and feels completely coated...and just like you, I also noticed the SIL was peeling on the tie-outs (but not on the fabric). Thanks as well for your sharing your write-up on how you coated yours. The basic differences I noticed were the Fabric and the ratio of silicone to mineral spirits

Originally Posted by nothermark

FWIW - I think you may also need to be careful about the solvent ratio. From what I know about coatings too much solvent leaves a porous coat when it dries.

I also think the massaging and squeegee are part of the process needed to work the material into the cloth. The cloth has to be open enough to accept the material. Some weaves are just too tight (I'm thinking peel ply as an example).

I'm thinking the main culprit was too much solvent and it left a porous coat as you mentioned. I've confirmed my ratio was 6:1 mineral spirits to silicone which I know from my research is twice the solvent that should have been present. I performed a crude test in a few spots with a bottle of water where I sealed the mouth against the fabric. Under normal gravity it held the water back just fine, but as soon as I applied any pressure to the bottle, the water came through the fabric in a seemingly perfect grid pattern of little dropplets.

Originally Posted by Rain Man

2. even commercial rainflies will get condensation on the bottom side and appear to be leaking, when they really aren't.

I'm familiar with this happening from my tenting days and trust me, it was deffinately leaking.

Originally Posted by zooshooter

Did you have the tarp hung tight like it would be regularly when you were working on it or did you soak it and then hang it loose to dry? It is important that you string it up after soaking it so that the fabric is under what will be regular operating tension, and then use a sponge to go over the fabric again while it is still wet from the initial soak.

I soaked it then hung it with weights on the tie-outs to dry but I did not follow up with a sponge and brush...looking back this was deffinately a mistake.

So after doing some reading on re-coating silnylon both here and here, I think I'm going to give the recoat a try. I plan on stringing it up tight (tie-outs included) to ensure the shelter is as it would be in the field then using the paint-brush method with the mineral spirits and silicone on both sides. I'm a little torn on what ratio to use as I think if it's too thick the new coat will peel but I might just try a 3:1 ratio as mentioned in the first article and see how it goes.

Does this sound like a logical approach or do you think I'm off my rocker? Either way, I'm still only $20 into the tarp materials and 1st waterproofing attempt so I have a little more room to play with before the expense starts to be painful.

**zooshooter** · 09-08-2013, 00:42

Originally Posted by schaapj

Does this sound like a logical approach or do you think I'm off my rocker? Either way, I'm still only $20 into the tarp materials and 1st waterproofing attempt so I have a little more room to play with before the expense starts to be painful.

Sounds good to me.

**schaapj** · 09-18-2013, 20:39

Re-coat is complete and fully cured. I used a 3:1 ratio of mineral spirits to 100% silicone by weight and painted it on the tarp from the outside using a 2" foam brush. The fabric soaked up the solution and wetted the inside as well so I chose to only coat the outside of the tarp. I made sure that before I started, the tarp was strung out tight as it would be in the field when using all tie-outs...it's a winter style tarp with doors and pull-outs.

The coating doesn't look nearly as pretty as it did before but I think this is only due to the application method of painting vs. dunking since the painted lines start to dry before starting the next row.

To test, I ran our oscillating sprinkler for about 3 hours with the hammock strung up under the deployed tarp checking it out and crawling in at various times (maybe nodding off once or twice

). My DIY hammock has an integrated bugnet so any water leakage should have been be plainly visable as splatter on the netting. I'm happy to report there wasn't a drop of water that fell on the hammock and the inside of the tarp felt dry everywhere.

Now I know that a yard sprinkler doesn't quite simulate the driving rain I experienced so I also sprayed the side of the tarp with a focused stream of water with an adjustable nozzle. Looking at the inside while doing this it did appear that a very fine mist was appearing on the opposited side. I'm guessing this is nothing to worry about as I wouldn't equate it to anything heavier than a fog but I'm hoping someone can reassure me of that.

So, assuming the "misting" with a close range and focused stream of water isn't anything to be concerned with, I think the next step is to test the durability of the coating and make sure it doesn't peel or have other negative side effects. I'll make sure to report back on my findings.

In the meantime, if there are any other things I should look out for, any questions or comments, or if I should be concerned with the misting I experienced in my testing feel free to chime in.

Thanks so much.
-schaapj

Oh, and here's a picture of my tarp in action shedding water like a champ

20130918_185922.jpg

**Klaussinator** · 09-18-2013, 21:09

Great job, sounds like it worked! Much of a noticeable weight increase?

We need more pics to accurately assess the situation ...

-Klauss

**XTrekker** · 09-18-2013, 22:05

Me and my friend used a foam brush also but only after dunking it in the solution. Have not tested it yet.

**schaapj** · 09-18-2013, 22:26

Originally Posted by Klaussinator

Great job, sounds like it worked! Much of a noticeable weight increase?

We need more pics to accurately assess the situation ...

-Klauss

Thanks! It appears if the coating is durable I'll have a good tarp on my hands.

Not positive about the added weight, but based on the amount of silicone I used it can't be over 7 oz. Once I take it down I'll get an actual weight and report back.

No additional pics...hopefully a video works instead

**schaapj** · 09-18-2013, 22:49

Originally Posted by XTrekker

Me and my friend used a foam brush also but only after dunking it in the solution. Have not tested it yet.

I'm guessing this is the one from your Marpat Hex Tarp thread? I'm looking forward to reading the test results. It'll likely save me some time next time around...both in fabrication as well as drying out wet gear

**olddog** · 09-18-2013, 23:22

Glad everything worked out for you. I went thru the same thing with my DIY tarp. Another unknown fabric/ unknown origin from WM but super light. After 3 attempts, brushing, sponging and dipping I would still get misting thru the tarp. Fortunately here in Florida our hanging season is also our dry season and in 2 yrs the tarp was never rained on. The DIY was out of fabric that began as about .75 oz./sq. yd and ended up weighing more than my Wilderness Logic Tadpole. DIY is fun but sometimes it can be more expensive than just biting the bullet and buying a quality product.