I seem to get most of my "good" MYOG ideas while hiking. Trucking out over the last hill Monday I was thinking about packs, and tarps. There's been a lot of debate concerning sil v. spinn v. cuben lately, and one of the virtues of the first two that is often overlooked is the ability to recoat them. Sil caulk plus mineral spirits is a pretty basic techniques, and works well.

So why not coat other nylons?

In spite of its very non-UL properties, I still like ballistics nylon in packs. Nothing I've tried (including DX40 and various lighter urethenes) holds up to egregious abrasion as well (think canyoneering). The tight weave even holds DWR and thus repels water surprisingly well, at least until it has a lot of use and gets a bit fuzzy.

So on Monday evening I cut a patch of ballistics from some scrap, mixed some special sauce, coated it, and let it dry for an hour then cure overnight. Nice light sil coating, almost invisible, but definitely there. Water beaded up in the distinct sil way.

So last night I mixed up a pint+ and coated my Black Diamond Demon (a ~40 liter 100% ballistics pack, meant for rock climbing, but with a curvy shape that is great for slipping through brush). With a paint brush you can work the juice into the seams and bartacks, and with a bit extra I did a double coat on the top, bottom, and back. I even brushed the (inverted) #10 zipper on the lid.

The effect is subtle enough that it can't really be photographed, but the pack is unmistakably now made of ballistics with a urethene coating inside, and a sil coating outside. I'll report back on long term durability.

I dabbed a bit on the bottom of one of my DX40 packs as an experiment, but that didn't seem to take as well. The 100% nylon might soak it up better.

That's a great idea

I wonder what would happen with 0.65 oz nylon?

I've recoated silnylon of bivy bottom - both inside and outside. The recoated silnylon on the bottom outside started peeeling off after a while. Maybe that's more abrasion than what you'de have with a pack.

What ratio of mineral spirits to silicone?

I was not at all scientific with my ratios. The dissolved solution was quite cloudy but still watery.

We'll see how durable it proves. I won't be totally shocked if the pack develops a skin disease in a few months.

It will be a good experiment

I coated my silnylon pack a couple years ago and used it many nights and it's still waterproof.

But that's different because the fabric was silicone coated to beging with so my coating had something to stick to.

There's an whole thread over on Hammock Forums (link to thread) about making sil. Admittedly, most of the fabrics they're working with are a lot lighter (usually in the 1.1 oz/sq yd range), but most of the folks who've done it have found that a ratio in the 3-to-1 to 10-to-1 range of solvent to silicone works pretty well.

Hope it helps!

Edited by FLRider on 09/05/2012 12:21:30 MDT.

I have done this on a couple occasions. Mostly with 70D nylon, not balistic or pack cloth, though. I used a 10:1 ratio, coating both sides. For touching up canopies, tarps, etc, I usually use 20:1 if the damage is just misting the inside a bit (not from condensation.) Again, both sides of the fabric. I find that thick coats, like 5:1, will peel on the second application. With 20:1 it does not. If the second coat is needed, then use it. I really cannot say about less dense weaves, though.

Makes sense that dillute coatings would be more stable. I've used them for sealing seams and beefing up a spinn tarp, and that has held up well.

I stumbled on Will Reitveld's suggestion for making a light cheap Tyvek rain parka -- and his followup note that it turned out to not be quite as waterproof as thought. What immediately ran through my mind was to wonder whether one could coat it as described in this thread. Would that work?

Robert, I have no idea, but there's only one way to find out. It would be an easy and cheap experiment.

We know from this site that even well engineered factory coatings on silnylon vary greatly in quality. So it is doubtful that brushed on coatings made from mixtures of sil and solvents are going to be any better than the worst factory coatings, probably worse. For misting silnylon flies, I've had good luck with Kiwi Camp Dry silicone spray (green can).