Sil-Poly Seam Sealing Question

I would contact Six Moon. I have seam sealed both SilNylon and polyurethane coated fabrics. Each requires a different sealer. I suspect silicone would work, but who knows?

edited to add: polyurethane won’t adhere to SilNylon, but silicone seems to adhere to most surfaces if they are clean or dirt or debris.

<p style=”text-align: left;”>Thanks for the response Nick. Now to be clear, I’m talking about silicone coated Poly, and not polyurethane coated fabric…2 different things I think.</p>
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I did a little research and think the Silnylon and Silpoly can be sealed the same way, but some consensus to use the stanky mineral spirits as opposed to low vox. Any other opinions?</p>

Ah… I know there are some sil-poly coatings.

I would think silicone would be the perfect solution, it will stick to the silicone coating.

I just use the pre-thinned windscreen sealant. Less mess and for the amont I use the cost is not an issue.

the other question is do you really need to do it?  Does water leak when it’s raining?

but it adds little weight, not that difficult to do, maybe just as well to do it and not worry

I have silpoly tent that I didn’t seam seal

Jerry, I have a few observations:

• It’s in the backpacking manual that you must seam seal your tent! It’s required and you can’t go off in the woods unless you do. It’s a rule.
• You are a backpacking stud! I’m imagining the first time you tried without the seam sealing….got everything wet…dang it.  Then you tried again…and  again until it worked!

In all seriousness,  the seams on this tent are robust so I may give it a try with a sprinkler. Thanks for the insight.

I’m just a lazy person

A wet lazy person

I think if it leaked, it wouldn’t be major, just a little

But, like I said, it’s not that big a deal and doesnt add significant weight so…

some consensus to use the stanky mineral spirits as opposed to low vox. Any other opinions?

Stinky all the way.  You never know what you’re going to get with those fresh-smelling or “green” concoctions.  I tried one once and–thank goodness I had the good sense to test it on something else first–it mixed up to a paste that stayed wet and gooey for weeks (no exaggeration).  Another kind I tried worked fine, but I’ll not be taking the chance any more.

There are some “green” paint thinners that don’t work

You want mineral spirits

Something like 5 parts mineral spirits to 1 part silicone, or 10:1 makes a pretty thin coating that soaks into seams pretty good

Thanks for all of the help…I appreciate the responses. Chris, I’ve never heard of pre-thinned windscreen sealant..have to check it out.

You’ve never heard of it?

There must be 100 previous threads about it:)

Well…..I searched and found 2 articles so I now consider myself edumicated. Interesting. I may just play around with both.

Although Jerry….this tent is for my son. I may take your original suggestion and tell him to go sit in a rainstorm and tell me what happens!

Russ,  Re: “I’ve never heard of pre-thinned windscreen sealant.”  Who’s on First?

It’s Permatex Flowable Silicone Windshield  Glass Sealant.  It’s at NAPA stores, or even from Walmart, online anyway.  Be sure to get the “clear”, not the black stuff.  I ordered two tubes from Amazon and got one, and they would not send me another.  That’s a big scam you know, ordering one tube and claiming you ordered two, and gypping Mr Bozo out of $6.

Moderator Roger Caffin has recommended Permatex not just for sealing, but also bonding silcoated fabrics.  Will be trying it per his instructions, and will post if it works better than GE sil glue, as recommended in an old BPL article.

The Permatex is plenty low viscosity for sealing seams on silcoated, but not PU coated tent surfaces, which adhere to SeamGrip.  And of course there is Silnet, available online.  There is a recent BPL thread about this.

RBTR started the confusion when they sold silcoated polyester as “silpoly,” maybe not realizing that the “poly” could also mean polyurethane (PU).  And there are some coatings out now that are a mix of PU and sil, so they could also be called “silpoly” to make it even more confusing.

Mineral Spirits are a petroleum product.  Petroleum is an oil.  Putting anything oily into a sealant is a recipe for peeling.  But if you need to recoat a whole silnylon or silpolyester tent floor, a tube of stuff is not convenient, so you’ve got to mix up something.  I tried campstove gas mixed with silicone clear caulk to seal seams on silcoated fabric, and it worked OK.  But for just sealing tent seams, it’s Permatex, no fuss, no muss.  There are plenty of reports on BPL of mineral spirits and silicone mixtures peeling off tent floors eventually.  Of course that could be because they were PU coated tent floors.

For waterproofing, as distinguished from water resistant treatments (DWR), there are a couple products for large areas like tent floors:  Tectron Heavy Duty Silicone Waterproofer, for silcoated tent floors and Tent Sure Tent Floor Sealant for PU coated floors, but their businesses have changed hands, so don’t know if they are still available.  Most of the other sprays, for boots, clothing etc are to refresh water repellence (DWR), not waterproofness, and will not block a material from being vapor permeable, or ‘breathable’.  But I did find that one of the better ones, from ScotchGuard, did visibly restore a silcoated tent fly.

Note:  Most if not all of the repellent sprays contain PFOAs, and may be toxic.  There is a thread on BPL about that also.  I’ve taken to using a gas mask and spraying outdoors when using these products.

If your silpoly is really pure sil then you can use the normal silnylon methods, but a lot of silpoly is really sil/pu poly where the coating can be (1) a blend, or (2) different on each side. For the latter you can use sil on the sil side. Not sure how to seam seal the former, nor which SMD is using. It appears that SMD recommends Gear Aid’s Seam Grip + FC for their poly tents:
https://www.sixmoondesigns.com/blogs/skills/faq-seams-sealing