Not all Sil-nylon is created equal!

You're absolutely right there, not all silnylon is created equal. And batch runs within the same mill can perform differently as well.

For example, I have not bought some rolls of Ultra-Sil that came back with test results I was not comfortable with, but on the whole, it is one of the highest quality silnylons out there. I do a full gallon water test and if it doesn't leak more than a couple drops all day, it passes my personal test. Most of the time I get no drip-thru at all.

2nds can be deemed so for a whole host of reasons, one being a higher than required CFM rate (air permeability, which is what silnylon is designed for, not for waterproofness).

Also – most companies that carry 2nds will have various "brandings" of 2nds – not that they can tell you which is which. That just means, some will be great and some will be good. You'd have to do your own testing on each 2nds fabric that is bought – can't do just one and think they'll all perform like that.

Sil is not as waterproof as something with a heavy urethane coating, but it is waterproof enough for the weight savings, in my opinion. And because it's waterproof enough, silnylon is great for tarps as the tarp sheds water before it pools enough to seep through. It might not be the best choice for a bivy or tent floor, as the pressure of your weight on it can sometimes (though rarely) be enough to cause seep-thru.

From what I've read there seems to be more than a couple of different fabrics calling them self some combination of "ultra" and "sil" that seem to perform differently also?

One of the advantages of buying your sil from someone like Scott at BWDD, or Paul at thru-hiker is of course the fact that they test fabric for "our" application, which the fabric companies seem to be indifferent about.

Bender,
Please try the Thru-Hiker or the Quest firsts (not the 'ultra-sil'). Both have been tested for me with a modified suter device, and tested best. Westmark also refers to its product as ultra-sil, but all three materials, the WM, Quest and RW are visibly different.
The Quest has recently been available in a medium-light tan, and the TH is available in a light gray. I went with the Quest tan for canopies, the T-H black for floors.

One qualification: The water penetration pressure tests do not tell us how the coatings will perform over time; in other words, what wears out faster. Two Stephenson's Warmlite samples were also tested for me, and did not perform quite so well, but they had a 'wet-look' coating, unlike the flatter finishes on the T-H and Quest, and I have to wonder if they would hold up longer. Still another issue is which ones will do better with recoating with various sprays and dilutions of silicon sealers. Only time will tell. I did find that older samples of silnylon with waxy or 'wet look' finishes made for much stronger welds with silnylon patches. Will soon experiment with welding together rather then sewing together the edge seams of the flatter finish materials (Note the recent reposted BPL article on welding silnylon).
Hope this is of interest, Sam

Interesting.
I have been , and still am, doing some experiments of my own.
Sometime ago I saw someone testing the waterhead using a pipe so I thought of doing the same.
(there is at least one purpose built unit that uses pressure to do that, however my budget is zero so I will skip trhat)
My pipe is 50mm wide and 3m long. It takes 8 liters to fill it so I use fractions of that to add 50cm of "waterhead" at a time.
The silnylon that I have passed the 1000mm test no problem but started to drip at 1500mm.
As you can see in the second shot water is penetrating the fabric, however after 4 hours the "drips" were still contained inside the base , so not actually dripping
as much as the shot seems to suggest. (the picture was taken after 2 hours of having filled the1500 mm of water.
After that I sprayed one sample with McNett silicone spray, just a couple of passes, and also coated another sample with a roughly 5:1 mineral spirit
to silicone solution. When this dried it was a lot less sticky than expected , so much less than my normal seam sealing finish.
The McNett bit held better the 1500mm but still let through two or three drops in a 3 hour or so period. The 5:1 version has been up
with 2000mm (4 liters) for a couple of days (because I was doing something else…) and it is still not dripping apart again from maybe a drop or so every few hours.


Franco
(the wet concrete floor is me spilling water…)

That's a nice little MYOG pressure tester Franco!

Some questions:

1. Looks like you are holding the fabric onto the end of the pipe with tape and then pushing a pipe coupler over the fabric, just using friction to hold it. Is that correct?
2. In the test you did with silicone diluted 5:1, did you treat one side or both? If one side, which side was in contact with the water?

Bender and Group, Thanks for the testing and discussion. Sourcing silnylon for my projects has been top of my mind this week so this is timely. I actually have an order coming in from Rockywoods that is 2 yds Ultra-sil and 2 yds of their regular 1.3 oz coated nylon. In the past I have only used thru-hiker for 1.3 oz. It has been good stuff, but colors are limited.

The ultra-sil sounded too good to believe and maybe it is. Lower weight with higher tear strength. Right now I'm looking for lightweight pack materials so tear strength may supersede waterproofness. Here is my list of potential suppliers and colors for 1.1 oz (~1.3 after coating).

– seattle farbics
Jade, White, Emerald, Lt Blue, Purple Navy Gold Orange Grey Black Flor Yellow
– QuestOutfitters
foliage green (dk olive), gray (ultrasil), tan
– owfinc.com
Black, Brown, Green, Med Gray, White
– rocky woods 1.3 oz
Estate Blue, Black, Neon, Yellow, White, Blue Jewel, Lime Green, Skydiver Blue, Neon Orange, Taupe
– rocky woods ultra sil
red, grey, white, black, royal blue, prism violet, kelly green, orange
– thru-hiker
black, smoke gray
– the rain shed – ultrasil
black, yellow, kelly

Hi Jim
1) yes
2) only coated one side , the one facing the water.
Not a very scientific test at all but it gives me a comparison. I still have no idea of the weight increase because i only coated a few small bits, too small to
register a different weight on my =/- 5 g scale.

Franco

Jamie, Scott has some at his BWDD site also, silicone impregnated cordura.

Here's the link: http://www.backwoodsdaydreamer.com/apps/webstore/products/show/932178

He's done some water tests with his fabrics too that seem to show good results, there are pictures on the site.

Javan, Thanks for the adding to my list with BWDD, it looks like they will get an order from me. I'm after some of the olive brown and at $8.50 a yards for first the price is best I've seen.

Ok my order from rockywoods arrived. I've got a yard of gray and red ultra-sil. I did the most unscientific test so far. I went to the bathroom, lined the sink with the ultra-sil and filled it half way up. I gathered it up, dryed it off (since the sink was already wet), and looked for any sign of water coming through. I did it twice and on one of the tests I could see one spot where a drop of water formed extremely slowly, but it did form. On the other test I didn't get any water to come through the ultra-sil. I did the water test on the std silnylon once and it didn't leak any water.

Interesting results as I definately did not get a bunch of little drops form. I'd say mine did a good job at holding water.

Here is a pic of the ultra-sil holding water…

I checked and the widths and yard cut are extremely close so I weighed them. The standard silnylon weighed 2.55 oz and the ultra-sil weighed 2.35 oz. The length wa 65" and width was 36.5" which is 1.831 yds. This gives a fabric weight of 1.283 oz/yd for ultra sil and 1.393 oz/yd for reg silnylon.

Not sure what to make of this I'm inclined to use either for pack making, but want to test the ultra-sil alot more before I accept it for tarps.

Jamie

> – seattle farbics
> Jade, White, Emerald, Lt Blue, Purple Navy Gold Orange > > Grey Black Flor Yellow
> – QuestOutfitters
> foliage green (dk olive), gray (ultrasil), tan
> – owfinc.com
> Black, Brown, Green, Med Gray, White
> – rocky woods 1.3 oz
> Estate Blue, Black, Neon, Yellow, White, Blue Jewel, Lime Green, Skydiver Blue, Neon Orange, Taupe
> – rocky woods ultra sil
> red, grey, white, black, royal blue, prism violet, kelly green, orange
> – thru-hiker
> black, smoke gray
> – the rain shed – ultrasil
> black, yellow, kelly

Bear in mind that all these guys are resellers. They don't make the stuff. Some of it is bought by the roll, others bits are left-overs from other companies.

Many if not most of these fabrics come from a single source: Westmark. The trouble there is that production runs seems to vary a bit in WP ratings, as the fabric is NOT made to be waterproof to a spec.

A few fabrics *might* come from full-roll purchases from China, made to order. There are Chinese companies who can do excellent coatings, but you have to buy 1,000 metres of a single colour. And you rarely get either samples or the opportunity to do any QC.

Cheers

Jamie
Some were impressed with the water test on the Scarp inner. (1 liter of water all day)

In reality it is only holding, in my picture, the equivalent of about 150mm waterhead.
Your bag is holding about 200mm.
Franco

I've got another great sil test that I use, which obviously isn't very scientific.

The squeeze test: Fill a pouch of sil, with however much water you feel like holding, I'm not sure that the volume matters. Cinch it up with your fist until most of the air is out, and then squeeze as hard as possible by holding the loose end with your free hand and running the fist down to the water pouch and cinching. Like you're trying to pop and upside down balloon.

I guess it depends on hand strength how much pressure you can simulate, but it's night and day compared to the "holding water" test.

I still have no idea of the weight increase because i only coated a few small bits, too small to register a different weight on my =/- 5 g scale.

Jim Woods Basecamp site estimates that treating both sides of the fabric with a 3:1 mineral spirits to silicone slurry adds about 3/4 of an ounce per square yard.

Jamie – got your order, you'll receive it this week.

Here's an extra twist to add to the thread. The Olive Brown silnylon that you ordered has a proprietary blend impregnation/saturation (which is mostly silicone), as opposed to a pure silicone saturation (like Ultrasil). In my very unscientific test, it held a gallon of water overnight with 4 drops coming through that I saw – bottom was completely dry in the AM, no measurable water loss beyond those 4 drops. You will notice a very distinct difference between this material and the other sil you've gotten used to.

Also – there is another "Ultra-Sil" fabric that is vastly different from Ultrasil. Ultra-Sil (being used by Sea To Summit for their UL drybags) is silicone coated one side, urethane coated the other side (so they can tape the seams). Unfortunately, this material is not available to the general public yet.

Keep up the research!

Yep, a good idea!

oops