silicone sealant

Im sure if its silicone based it could work. I honestly would just use some scrap and try it out. Never know if it has some chemical that the nylon might react to.

100% silicone is packaged for many purposes, and as long as it's 100% it should work. If you're unsure of the ingredients, testing on scrap is definitely a good idea. 100% silicone caulk (in the big caulking-gun tubes) is perfectly usable too, and cheaper than silnet. I do recommend thinning down 100% silicone first, 2 or 3 parts mineral spirits to 1 part silicone.

There are a million different formulations of 'silicone' sealant. However, most of them work the same. If it was used on fishtanks it would be fine on any silnylon. It is probably very similar to McNett silicone or the Permatex stuff some recommend.
You should grab a box-full and distribute it to a select number of people … :-)
Just remember that once a tube has been opened the contents will start to cure, and so have a finite life before it is all solid.

I recently bought a Gatewood cape. When I sealed it, I bought a tube of GE II Silicon caulk to use. I'd always read to dilute it with mineral spirits. recently I talked to a guy over at Kifaru who uses it straight, smoothing it along the seam by wetting his finger with saliva to wet it and smooth it along the seam.

Since the cape has two long seams, I did one seam with the 'diluted with mineral spirits' technique and one seam without diluting it, smoothing it with my freshly licked finger.

It'll will be interesting to note any differences in performance, especially in regards to long term use.

How did the undiluted side turn out? Was it a super heavy extra thick coat. How does it compare ascetically to the diluted side. I am making a tarp-tent (not a henry shires, i just don't know what else to call it) and if the undiluted looks as good i may give that a try too. Will the added weight be significantly more with the undiluted?

Just tried it undiluted on an old stuff sack I had laying around. When it dried, it was real grippy, but very water proof. Not a lot of weight added either. Just applied with my finger in a thin layer. So far so good, Next I'll try it on an old tarp. Thanks for the input guys!

The sealant should work on silnylon or silicone coated fabrics. It will probably peel off fairly quickly if applied to other fabrics. Test it first.

The diluted side has a rather dull, 'soaked in' look. You have to examine the seam closely to see that it was sealed.

The undiluted side is shiny, and is obvious from a distance that it's been sealed. As the other poster pointed out, it's very waterproof. It's also kind of 'grippy' or sticky in texture.

Overall, if the long term performance is equal, from now on I'll use it undiluted simply because it was simpler (no mixing, stirring, cleanup, etc). Just squeeze a fine bead along the seam, and smooth in with a wet finger.

I use silicon to caulk sinks to stone at work. After applying the bead of silicone completely covering any gap. Us denatured alcohol diluted 50/50 with water in a spray bottle. once the alcohol is sprayed over the bead, the silicone wont stick anywhere the alcohol is now. Makes cleaning up much easier. Less residue left over. Im gonna try this on my proto bivy im making. Ill see how it works.