Siliconized nylon, more commonly called silnylon, is a waterproof fabric used to make tents by many smaller manufacturers including Six Moon Designs, Tarptent, Mountain Laurel Designs, and Hilleberg which specialize in making ultralight backpacking gear or expedition-grade tents. It’s also sold in bulk for DIY-ers by Ripstop-by-the Roll, for people who want to make their own tents and tarp shelters. Some companies like Lightheart Gear and Anti-Gravity Gear also use silnylon to make rain jackets.
Silnylon is available in different thicknesses, weights, and levels of waterproofing so it’s important to understand how the “waterproofness” of fabrics, is measured when comparing tents or rain jackets. Some silnylons are also coated with polyurethane, abbreviated as “PU” as in “Sil/PU”, and are best thought of as a separate fabric type, since it changes the properties of the fabric in a fundamental way. When people talk about silnylon, they really just mean siliconized nylon.
Waterproofing is measured using the hydrostatic head test, which measures the amount of water pressure a fabric can withstand before water starts to bleed through it. A column filled with water is placed over the fabric. As more water is added to the column, the pressure on the fabric is increased. When droplets of water begin to soak through the fabric, the height of the column is measured in millimeters and becomes the waterproof rating of the fabric.
For example, both the Six Moon Designs Lunar Solo Tent and the Tarptent Moment DW have a 3,000 mm waterproof rating (ie. hydrostatic head) on their rain flies and floors. The same waterproof rating test is also used for other fabrics including Dyneema DCF and Silicone Polyurethane (Sil/PU) treated Nylon, which is also used to make tents and rain jackets, making it possible to compare the waterproofness of tents or jackets made with different materials. Keep in mind that there are also many grades of Dyneema DCF and Sil/PU Nylon, so it really depends on what grade of material and waterproof coating formulation was used for a particular tent or jacket when making comparisons.
Waterproofness Comparison of Different Tents based on Hydrostatic Head
Many companies use a separate waterproof treatment on the rain fly and floor of their tents, since the floor is often subject to higher pressure (someone sitting on it in a puddle) than the fly and because ground abrasion wears down the floor’s waterproofing with use.
|Make / Model||Rain Fly||Floor||Fabric / Material|
|Big Agnes Copper Spur HV UL 2||1,200 mm||1,200 mm||Sil/PU Nylon|
|Big Agnes Tiger Wall UL 2||1,200 mm||1,200 mm||Sil/PU Nylon|
|NEMO Hornet 2||1,200 mm||1,200 mm||Sil/PU Nylon|
|MSR Hubba Hubba NX2||1,200 mm||3,000 mm||Sil/PU Nylon|
|Gossamer Gear The One||1,200 mm||1,200 mm||Sil/PU Nylon|
|Durston/Drop X-Mid 1||2,000 mm||2,000 mm||Sil/PU Polyester|
|Tarptent Moment DW||3,000 mm||3,000 mm||Silnylon|
|Six Moon Designs Lunar Solo||3,000 mm||3,000 mm||Silnylon|
|Hilleberg Niak||5,000 mm||12,000 mm||Silnylon (Fly) PU Nylon (Floor)|
|Tarptent Aeon Li||8,000 mm||8,000 mm||Dyneema DCF|
|Hilleberg Nammatj 2||5,500 mm||20,000 mm||Silnylon (Fly) PU Nylon (Floor)|
|Zpacks Duplex||15,000 mm||20,000 mm||Dyneema DCF|
While the waterproof rating of Silnylon is a useful piece of information, silnylon tents and rain jackets can also leak at the seams, unless they’re seam-sealed with silicone. When silnylon is sewn, the needle and thread create many needle holes in the fabric that can leak in the rain. Unlike Sil/PU coated nylon or Dyneema DCF, these needle holes can’t be taped closed because the surface of silnylon is too slippery and tape can’t adhere to it. Most of the manufacturers who sell silnylon tents offer a seam-sealing service to you when you buy a tent from them, although it costs extra and will increase the weight of your tent by an ounce or two.
Companies that make rain jackets with silnylon use what’s called a bound seam to join together panels of fabric. This type of seam is very water-resistant but not waterproof. If you need it to be waterproof, for instance, if you have to hike in cold and wet conditions where hypothermia is a risk, you’ll want to seam-seal it yourself. This can be a messy process with a rain jacket and it’s often worth buying a seam-taped rain jacket instead.
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