Companion forum thread to:

Make Your Own Gear: Sealing Silnylon Seams

Looks good Jay. I have done it that way many times, and it works just fine as you said.

However, it might be worth mentioning that there are other ways of sealing silicone seams as well.

1: I have often used a large hypodermic syringe (without needle) to run a bead of the silicone sealant along the seam. This can be done with the thinned stuff, or with the unthinned stuff. The latter just requires more force on the plunger. I push the hypo forward as the bead comes out: the end of the nozzle forces the sealant into the seam. Of course this leaves a bead, so I then run my finger along the seam and FORCE the sealant into the stitching. Yeah, you get messy fingers, but the stuff rubs off skin when it has cured for a couple of hours. In any event, curing takes a day or two (or three).

2: You can use ordinary clear silicone sealant from a hardware store instead of the far more expensive SilNet. It behaves pretty much the same. I prefer the non-acid cure stuff, but the acid-cure stuff seems to work just as well. I reproofed the entire floor of my tent in France like this - with my fingers. Messy, but it worked.

3: You can buy siloxane transfer tape for silicone surfaces from some of the more specialised adhesive tape suppliers. Caution: it is expensive! I use this on a lot of my gear. I make up an adhesive fabric tape by running strips of the transfer tape onto silnylon fabric, usually about 12 mm (1/2") wide. This is much less messy of course, but you MUST allow 3 days for the adhesive to fully cure onto the silnylon fabric. Strange chemical bonding goes on. This has the distinct advantage that by placing a 12 mm tape across a seam you take a huge load off the stitching: the adhesive bond across the seam takes the load. Yes, I HAVE tested this extensively. (Sailmakers do this too with the very light PU-coated spinnaker fabrics.)

4: I know of at least one and possibly two guys who have used silicone sealant from a hardware store instead of the transfer tape on a whole tent. This is more difficult as the sealant has virtually no 'tack', so you need to make sure the pieces of fabric are pressed together very well and left for a couple of days for the sealant to cure. I haven't tested this very much myself.

Cheers
Roger

"Jim Wood's Basecamp" promotes the same idea and it works great.

Folks with a postal scale that can report in grams might consider a 3:1 (by weight) slurry ... it's somewhat easier to make small batches that way. Small batches mix up well in recycled (and cleaned) tuna cans.

edit: And it is well worth the extra cost to use odorless mineral spirits for this

Edited by jcolten on 09/05/2007 08:00:47 MDT.

Talk about timely. I was just talking to my wife about how I needed to seam seal a shelter. Kind of creepy really ;)

Tom

Does it make any sense to seal the seams while the fabric is under tension? I just seems to that it might work better for some reason (not that I know what that reason is!).

yep, applying the sealer under tension allows the sealer to fill all holes & seams the way they will be stretched in the wind, reducing the stress on the sealer in high winds.
i'm sure this increases the strength of the seams & stitching in high winds too.
let it cure as long as you can, but if you need to pack it for a trip & it's still a little tacky, just brush talcum or baby powder over the new seam sealer (both sides).
that will keep it from sticking to it's self when packed.
i'll let others comment on the pros & cons of having a scented tent in critter country. ...tim

Never mind critters. I made the mistake of using Johnson's baby powder (once). The smell is a bit strong for comfort, made me think I was sleeping in a nursery, and it lingers.

Generally, I have not found that the cured silicone needs a powder cover, even thicker anti-slip layers on the floor. I've yet to see any problems with a tent sticking together in storage. This mixture cures fast.

I sealed a Shires Double Rainbow with GE Silicone diluted with mineral spirits (and yet another Double Rainbow with the Mcnett product, somewhat less successfully). The gain in weight was about one ounce for the one with GE Silicone. It might have been less, had I applied sealant to a narrower band along the seams, but my local hardware store didn't have thin foam brushes. Having the tent up and tautly pitched seems to me to be essential, for the reasons touched upon by a previous poster.

One thing not mentioned in Jay's article is that a thin solution of sealant in mineral spirits can be used to rewaterproof dodgy areas on silnylon. I have an Equinox poncho that I use (in addition to its intended purpose) as a groundsheet, tarp, waterproof pack lining, etc. etc. It's held up well to this abuse but before the weather cools I intend to recoat it with a thin silicone slurry. This might also be a worthwhile procedure for silnylon which is not particularly well treated at the outset, I would expect.

One further point is that silicone isn't that readily soluble in mineral spirits. Not bad, but it can take a fair amount of mixing to get a solution in which the silicone's evenly distributed. I make mine up the night before, in a sealed jar, then shake heavily before use. It will keep some while if the jar is airtight, BTW.

Thank you, Roger, for the interesting information on silicone tape. I have to look into this.

Edited by edwardripleyduggan on 09/07/2007 18:07:51 MDT.

> One thing not mentioned in Jay's article is that a thin solution of sealant in mineral spirits can be used to rewaterproof dodgy areas on silnylon.
Too right. As I mentioned, I recoated the entire floor of my tent with just my fingers to spread the stuff, and it worked great.

I was just going to seam seal my brand new MLD poncho that came in.

I seam sealed a Gatewood Cape and used it in the Wind Rivers for 5 days. Had a really good blow one night, and lots of rain. No leaks at all.
For seam sealing, I like to stretch the seam, and weight either side to keep the seam "open". Then I apply the sealer. In this case Mcnett silicone. After it's cured, I'll remove the weights to let the seam "relax". Kind of laborious, but it works.
I've never experienced cured silicone layers sticking to one another. I've found cured Mcnett seamgrip layers notorious for sticking to one another. I usually use climbers chaulk to coat the cured seamgrip with good results.
Paul

i need to seal a seam near the top of my atko fly---questions---does anyone know what mineral spirits are called in UK?---do you clean seam before applying sealer?----i was going to erect tent then seal seam from the inside -is this practical?---thanks in advance for any answers

Hi Barry

> does anyone know what mineral spirits are called in UK?
Nope, but try asking for 'thinners'. I have used turps, petrol, and even silicone oil. All worked.

> i was going to erect tent then seal seam from the inside -is this practical?
Potentially dangerous! The build-up of solvent vapour inside the tent could be lethal.
I have used undiluted silicone sealant inside a tent - that's OK.

Cheers

thanks for reply roger -re sealing from inside tent-i have only got to seal about a foot of leaky top seam seam so i was hoping to be in and out fairly quickly--this will be similar to painting a ceiling --in your opinion will the thinned sealer penetrate the seams or just all drip down on to the ground?---should i try and pitch the fly inside out and seal from the outside?--i like the idea of sealing with some tension on the material to aid penetration----regards barry

Is there a way you can remove sealant?
I presume its not by washing it with water... but it does interest me. For example say you need VB clothing, but only for one trip, you could seal up a wind shell, and then not have to buy another piece of gear. Also you could get something with a hood, and then you would have VB headwear which is not made at all.

Hi Barry

> i have only got to seal about a foot of leaky top seam seam so i was hoping to be in and out fairly quickly
Ah, OK. Leave the tent doors wide open and watch yourself. Or, if married, have wife monitor your state of conciousness...
Don't use petrol: it has too many volatiles. And preferable do it outside: why stink up the house.

> will the thinned sealer penetrate the seams or just all drip down on to the ground
Oh, a 3:1 solvent/sealant ratio still gives you a pretty goopy mess, as Jay said. Put it on with a foam brush carefully, and it will do a great job. Btw: I make my own foam brushes with some 1/2" open-cell foam sheet and a stick and some string.

> sealing with some tension on the material
I think Jay recommended this. I totally agree.

Cheers

Hi Jonathon

> Is there a way you can remove sealant?
Yeah, with a LOT of patience and considerable violence. :-)

Actually, it depends on the surface. On many surfaces silicone sealant sticks ... like onto a blanket.
On an oily surface it will probably peel off with some effort, and on a fluorocarbon DWR surface I think it will also peel off. Silicone polymers and fluoropolymers are just NOT compatible, so don't try mixing DWR sprays with silicone sprays on fabrics.

> VB headwear which is not made at all.
Plastic bag over the head ... :-)

Is there any sort of sealant that would work. The stuff like nikwax or plain ole seal oil come to mind, but I hope theres something that could be moderately easy to do once or twice a season.

As for a plastic bag, i tried that when I was a little kid and didnt know better, and I have to say that i could use more ventilation options.

Edited by hotrhoddudeguy on 09/08/2007 15:57:42 MDT.

Roger:
Might you supply the names of several online suppliers of the Siloxane tape you mentioned. I am wondering if this would work well on something such as the SD Isotope jacket or would the use of the McNett Slurry be better?
Thanks for your always timely comments.

Hi Mitchell

> names of several online suppliers of the Siloxane tape you mentioned.
Problem there. These tapes and the adhesives are very new, and most of the vendors do the stuff as a custom order with a minimum order quantity - usually about a thousand dollars. I was able to get some samples here and there. The situation will change over time, but it is expensive and unlikely to ever be over-the-shelf very often.
That said, the single-sided Husky 2500 tape may be available off the shelf. I have used it for seam sealing, but let it cure in place for three days. It uses a polyester (I think) film carrier, which is a shade heavy on silnylon.

> I am wondering if this would work well on something such as the SD Isotope jacket or would the use of the McNett Slurry be better?
That's a PU-coated fabric, not silicone, and the jacket is meant to be seam-sealed already. You could use a PU tape or adhesive on that, or a 'seam-stick' tape such as the sail-makers use. But if the jacket needs repairs, might it not be better to return it to SD under warranty?

Cheers
Roger Caffin

Thanks Roger for the info on the Siloxane tape.

I had forgotten that the Isotope was PU coated. The reveiws of the isotope indicated that SD had made a change in the production of the jacket to account for the leakage reported around the pockets by fully taping them. Turns out that that is not the case. I bought the jacket thinking that the problem has been addressed, but found that it had not. After speaking with SD about it, I found that they never intended to seal the pockets and don't plan to do so in the future. So, I am looking to do the job myself using one of the seam sealing tapes as you suggest.

Thanks Again
Mitchell