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Silnylon vs Poly coatings
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John G
(JohnG10) - F

Locale: Mid-Atlantic via Upstate NY
Silnylon vs Poly coatings on 01/19/2010 18:22:30 MST Print View

How do you tell if the "coated ripstop" fabric at the local store (Jo-Anns Fabric, etc) is silicone coated or polyeurathane coated ? The people in the store didn't have any idea, and the fabric bolt nor vendor catalog said anything about the coating.

ps: I need some fabric to make a tarp for this weekend, so ordering from Thru-hiker or OWFINC is out.

Also, for "next time" does anyone know where to get the fabric that the mainstream gear manufacturers are using for tents - it's Silicone coated on the outside, but poly coated on the inside. I think they use it so taped seams work. I'd like to use it for the much greater hydrostatic head.

Javan Dempsey

Locale: The-Stateless-Society
Re: Silnylon vs Poly coatings on 01/19/2010 20:28:42 MST Print View

Good luck, I posted a question like this once, but the answer isn't easy.

What I can tell you is this: You'll know when you know.

I know that sounds sarcastic, but that's not my intent. It's hard to explain an easy way to tell, without taking some home and testing it, but once you've seen the difference with your own eyes, it's pretty obvious. I've personally only seen Silnylon at Jo-Anns or any other fabric store once. PU coated Polyester I've seen as fabric for making raincoats. All the nylon they carry is generally either un-coated, or, DWR treated. The stuff that feels slicker on one side, but you can still blow breath through easily, is probably DWR.

The PU coatings I've seen, look noticably coated, like plasticky on one side. DWR doesn't change the fabric look, but the feel is different, same with Silicone impregnated, but the feel is even more drastic.

Dunno if that helps, might want to try to eyeball some PU coated polyester (which I've seen lots of at Jo-Ann), if you have to be waterproof, or use something else. Lots of other options for a tarp besides nylon.

Hope I got all that info right, good luck!

James D Buch
(rocketman) - F

Locale: Midwest
Fabric JoAnn or Hancocks on 01/20/2010 08:02:52 MST Print View

I have shopped both Joann and Hancock stores for outdoor fabric with negative results.

Often the store help don't know the difference between waterproof (Coated) and water-repellent. They just sell what they have.

The staff who know the fabric business will generally tell you that you have to go online to buy these things today.

The sewing market is smaller and different from what it was in the 1970's when the first wave of DIY backpacking/camping gear hit. More than 30 years have passed, and coated outdoor fabrics for DIY have become harder to get.

I have occasionally been able to buy coated nylon or silnylon at the WalMart bargain bins, but I have not found any in the last two years in the single remaining Wally that carries fabric in my area.

Marc Penansky
(MarcPen) - F

Locale: Western NC
Silicone Coated vs Polyurethane Coated Fabric on 01/20/2010 09:01:07 MST Print View

The best way to tell the difference between silicone coated and polyurethane coated fabric is to take a swatch and put a dab of silicone seam sealer or silicone caulk on it and let it dry. Once dry, the silicone seam sealer or silicone caulk will only stick securely to the silicone coated material. The silicone sealer or caulk will rub off the PU coated material easily.
This is a definitive test for differentiating between these two materials but may not be correct if it is neither material. If it is uncoated material, you will be able to blow through it and a shallow pool of water should seep through it easily. It is also possible that the material is only coated on one side (some sil-nylon is only coated on a single side) and it can be difficult to tell which side is coated even though we would all think it is obvious.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Silnylon vs Poly coatings on 01/20/2010 13:49:02 MST Print View

Tricky stuff.
Once you have seen and handled silnylon you won't have any trouble IDing it.
PU coating is usually a bit dull and definitely air-tight when you blow from the coated side. Don't try from the uncoated side: that leaks through the fibres.

Now for the big one: acrylic coating. This is used on a lot of fabric sold in the 'ordinary' shops because it is much cheaper. It is shiny compared to PU coating. It is often used to bind the weave together rather than to make the fabric waterproof - which it does not do very well anyhow. If you get some light nylon fabric at a local store and the coating is a bit shiny; odds are it is acrylic. Good for shower curtains, lousy for rainwear, pretty poor for tents.


Scott Littlefield
(sclittlefield) - F

Locale: Northern Woods of Maine
sil/pu coating on 01/21/2010 11:35:13 MST Print View

There is a fabric called "Ultra-Sil" (different from "Ultrasil") that is silicone coated on one side and pu coated on the other. Sea-to-Summit has a newer line of stuff sacks that use this material and you're right - it's so one side can be seam-taped.

Finding a distributor of the material is a whole other issue. I've been looking for some time now and have yet to find it.

You may try here:

They list their silnylon as "Ultra-Sil", but I have yet to contact them to find out if it is actually "Ultra-sil" or "Ultrasil". I'm guessing it's just a silicone finish, as there is no information about a different sided coating.

I carry Ultrasil and make most of my tarps from it ( It's great stuff as far as pure silicone nylon goes.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: sil/pu coating on 01/21/2010 14:56:32 MST Print View

> Finding a distributor of the material is a whole other issue. I've been looking
> for some time now and have yet to find it.

That's because there usually is NO distributor. What has happened is that S2S will have commissioned a few rolls from a coating plant somewhere (China or Korea) and bought the lot. Several other firms have done something similar as well.

"No you can't have it: it's all mine!"


Brian Kelly
(bkelly) - F
not just for seam taping on 01/21/2010 20:55:48 MST Print View

The other reason that companies will sil coat one side and PU coat the other is to add a fire retardant in order to pass the CPAI-84 fire retardancy standard. The fire retardant is typically added to the PU mixture when it is applied.

Jared Dilg
(Village) - MLife

Locale: Texas
Silnylon at JoAnn on 01/21/2010 22:01:42 MST Print View

For what it's worth John, I just picked up some silnylon rip-stop from JoAnn this evening using their 50% off coupon good through Saturday. Ended up $3.50/yd. I went there looking for DWR rip-stop to make a hammock. Despite it passing the blow-test (no air would pass through) I was incredulous and bought it anyway. Rubbing your fingers over silnylon feels greasy, though nothing is left behind. So far it's holding 1/2 cup of water without wetting or leaking and the silicon adhesive is firmly stuck to it. I guess I'll make a tarp out of it and search for hammock material somewhere else.

Backpack Jack
(jumpbackjack) - F

Locale: Armpit of California
RE Silnylon on 01/21/2010 23:32:54 MST Print View

Jared where do you live? I went to our Joanns and all they had was just regular rip stop nylon.

Jared Dilg
(Village) - MLife

Locale: Texas
Silnylon on 01/22/2010 00:04:05 MST Print View

I'm in Austin, TX. They had red, yellow, black, blue, & grey silnylon in stock, but no standard rip-stop. Go figure.

The larger bolt of grey silnylon was actually two cuts of 3yd and 9yd. I'm going back tomorrow to get at least 4 more yards to pair up with the 9yd piece and make a decent tarp for a hammock. What do you all recommend I do with 3yds of fabric, other than make a ton of stuff sacks? Is it big enough for one side of a tarp tent?

Edited by Village on 01/22/2010 00:04:45 MST.

Tim Marshall
(MarshLaw303) - MLife

Locale: Minnesota
Re: Silnylon on 01/22/2010 08:09:34 MST Print View

3yds should be big enough for one side of a tarp or tarptent. Just depends on the design you're using.

Also makes a nice 5'x9' flat tarp


Jared Dilg
(Village) - MLife

Locale: Texas
Re: Re: Silnylon on 01/22/2010 10:33:23 MST Print View

It is big enough? Great - I had searched for commercial tarps all last night to find an example that was less than 10ft on the ridgeline but no luck. Just assumed that it shouldn't be that small. My short piece is 3yds 4in, and the width is 60in including the selvage. Does this short length dictate that I use say a diamond pattern compared to a hexagonal tarp with cat cuts?

Bob Gross
(--B.G.--) - F

Locale: Silicon Valley
Jo-Ann Fabrics on 01/22/2010 17:09:23 MST Print View

I checked it out at a local store. It turns out that there is completely different pricing and discounts between online and stores. So, beware.

The local store here had a modest assortment of sport nylon in different colors and ripstop nylon in different colors. Only time will tell how great they are.