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.