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|Best for Silicone-coated Fabrics: Gear Aid Seam Grip SIL (f.k.a. McNett’s Sil Net)|
|Best for Polyurethane-coated Fabrics: Gear Aid Seam Grip FC (f.k.a. McNett’s Seam Sure)|
|DIY Sealer for Silicone-coated Fabrics: GE Silicone II Caulk + Odorless Mineral Spirits|
I recently bought a new tent, a Six Moon Designs Lunar Solo.
When placing the order I had to decide whether to get it with or without seam sealing. I opted to save some money and get it without seam sealing, but that decision led to questions.
Which seam sealer should I use? Should I go the DIY route or buy a brand-name sealant?
I realized that many other backpackers were sure to have these exact same questions. So I set out to find some answers.
To do so, I conducted email interviews with representatives from four well-respected ultralight backpacking gear companies and one from a top seam sealer brand, Gear Aid, to get their take on seam sealers.
Their answers were illuminating, and they’ll help you find the best seam sealer for your tent, backpacking tarp, and beyond.
McNett’s Is Now Gear Aid & They’ve Renamed Their Seam Sealers
Before we dive in to the reviews, it’s important to clarify that McNett’s — a popular seam sealer brand — is now Gear Aid.
Eloisa Townsend, Events & Communications Specialist at Gear Aid, sent me the following explanation:
“We are still the same company that manufactures the same care and repair products. We now have different ownership, so we’ve rebranded to bring all our various products under the one GEAR AID brand.”
Along with the rebrand Gear Aid has renamed their seam sealers.
- McNett’s Sil Net is now Gear Aid Seam Grip SIL
- McNett’s Seam Sure is now Gear Aid Seam Grip FC
- McNett’s Seam Grip is now Gear Aid Seam Grip WP
“Only the names have changed to make it easier for our customers to choose the right product for their repair needs,” said Townsend. “The formulas remain the same.”
For the remainder of this article I will use the new names for each sealer.
Best for Silicone-coated Fabrics: Gear Aid Seam Grip SIL
Three out of the four representatives I talked to recommended using Gear Aid Seam Grip SIL (f.k.a. McNett’s Sil Net) for silicone-coated fabrics such as silnylon and silpoly (see this special note on silpoly).
“It has been the industry’s standard for years,” said Whitney LaRuffa, Sales and Marketing Manager for Six Moon Designs. “It is a proven product and we find it is the easiest product to work with off the shelf.”
“For silnylon shelters, I’ve always used [Gear Aid Seam Grip SIL],” said John West, founder of Borah Gear.
“It’s great stuff and packaged in a small consumer one tent volume tube,” he said. “You can use it straight from the tube.”
Henry Shires, founder of Tarptent, was the only one not to recommend Seam Grip SIL.
“We recommend our kit,” he said. “In our experience the commercial products are too thick and hard to apply. The exception, still a little thick but much better, is Permatex Flowable Silicone Windshield and Glass Sealer.”
West agreed with Shires about the viscosity of the commercial products. “The silicone-based sealers can sometimes be a bit thick,” he noted.
However, West went on to say that thinning the sealer helps with application.
“If you’re doing long tent seams,” he explained, “I’ve found that putting some of your sealer in a dish and then thinning it down some with mineral spirits makes it easier to brush on.”
Best for Polyurethane-coated Fabrics: Gear Aid Seam Grip FC
Some tents are made out of a fabric, such as polyester, that is coated in polyurethane.
For this type of fabric, two out of three gear makers preferred Gear Aid Seam Grip FC (f.k.a. McNett’s Seam Sure).
“For PU-coated tents and DCF/Cuben Fiber use the Gear Aid Seam Grip FC Tent Seam Sealant,” said Bell.
“We personally carry [Seam Grip FC] as it is easier to work with as it is water-based and is easy to clean up,” said LaRuffa.
Another top seam sealer for PU-coated tents is Gear Aid Seam Grip WP (f.k.a. McNett’s Seam Grip).
On their website Six Moon Designs recommends either Seam Grip FC or Seam Grip WP for polyurethane-coated polyester. I asked LaRuffa if they had a preference. It turns out they do.
“The two items differ as [Seam Grip WP] tends to be thicker and goopier making it harder to apply for the inexperienced seam sealer,” she explained. “Either item works great so that is why we recommend both. From a consumer standpoint the [Seam Grip FC] is easier to clean up and therefore the one we prefer.”
West, the third gear maker who gave a recommendation for PU-coated fabrics, preferred Seam Grip WP.
“For silpoly and other PU-coated fabrics, [Seam Grip WP] is usually the way to go, and the only urethane-based sealer that I’ve ever used,” he said.
It seems you can’t go wrong with either.
Shires didn’t give a recommendation for PU-coated fabrics. “We only have experience with seam sealing silicone-coated fabrics,” he explained.
DIY Sealer for Silicone-coated Fabrics: GE Silicone II Caulk + Odorless Mineral Spirits
Some campers and backpackers go the DIY route and make their own seam sealer. I asked the gear makers for their thoughts on how the DIY sealer compares to the brand-name options.
“If you’ve got a DIY type mindset, mixing some silicone with mineral spirits works just fine and is cheaper in the long run,” said West. “Make sure to use 100% pure silicone, the clear kind in the tube. I always started off with around a 1:1 ratio, and then thinned it from there as I saw fit. If you have a few tarps/tents to seal, I’d go this route instead of buying multiple tubes of [Gear Aid Seam Grip SIL] or similar.”
Other respondents had good things to say about the DIY sealer. According to Shires it’s “easier to apply.” According to LaRuffa, “the DIY seam sealer is prettier; it drys clearer, thinner and it penetrates the seams better.”
It even turns out that Mountain Laurel Designs uses a DIY sealer. “In the shop we seam seal using large tubes of 100% GE Silicone II Clear caulking diluted 1:2 with 100% Odorless Mineral Spirits,” said Bell.
Be aware that a DIY seam sealer consisting of silicone mixed with mineral spirits is only for silicone-coated fabrics.
“The DIY seam sealer only works on fabrics that are coated in silicone for their waterproof layer,” LaRuffa explained.
Interested in going the DIY route? Here’s how to do it.
- GE Silicone II Caulk
- Odorless mineral spirits (“Do not use paint thinner or the easy clean up Eco Mineral Spirits,” says Bell.)
- Foam brush
- In a container, mix one part mineral spirits with one part silicone caulk. You can mix by hand or with an electric drill paint mixer. Stir well until thoroughly mixed.
- If needed, continue thinning the mixture with mineral spirits until it reaches the desired consistency. It should have a “warm honey” consistency according to Tarptent. SMD says it should be “smooth and milky, and flow evenly when applied.”
- Use the foam brush to apply the sealer. Be sure to seal your tent in a well-ventilated area.
- Wipe off the excess with a paper towel. This also helps force the solution into the seams.
- Optional: Paint stripes on your tent floor. The stripes will help prevent your backpacking sleeping pad from sliding around.
- Let the silicone cure. SMD recommends waiting 8-12 hours.
- Check your work by pitching your shelter and spraying it with a hose to see if water leaks in through any of the seams.
Tarptent made this helpful video showing how to mix and apply the DIY seam sealer.
Here are the best tent seam sealers:
- Gear Aid Seam Grip SIL
- Gear Aid Seam Grip FC
- GE Silicone II Caulk + Odorless Mineral Spirits
How to Choose the Best Tent Seam Sealer for Your Needs
Before picking a seam sealer you’ll need to find out whether your tarp or tent is made from a silicone- or polyurethane-coated fabric.
Silicone-coated fabrics such as silnylon and silpoly need to be sealed with a silicone-based seam sealer. Only silicone will adhere to silicone. The brand-name silicone-based sealer most recommended by respondents was Gear Aid Seam Grip SIL (f.k.a. McNett’s Sil Net). The DIY sealer described above is also silicone-based.
Polyurethane-coated fabrics need to be sealed with a urethane seam sealer. The brand-name urethane seam sealer most recommended by respondents was Gear Aid Seam Grip FC (f.k.a. McNett’s Seam Sure). Gear Aid Seam Grip WP (f.k.a. McNett’s Seam Grip) is another good option.
Dyneema/Cuben Fiber shelters generally do not need to be seam sealed.
A special note on silpoly: silpoly sometimes has a silicone coating on one side and a polyurethane coating on the other. This version is sometimes called SilPolyPU. If your tent is made from SilPolyPU you’ll need to contact the manufacturer to find out which side is coated with silicone before seam sealing.
For further reading on tent fabrics, see Yama Mountain Gear’s excellent breakdown of shelter materials.
Number of Tents You’ll Be Seam Sealing
If you only need to seam seal one or two shelters, a tube from Gear Aid will likely be all you need. If you’re unsure whether one tube will be enough, Gear Aid lists the number of inches a tube seals on their website.
If you need to seam seal many tents, it will be cheaper over the long run to purchase the ingredients for a DIY sealer.
Thinner seam sealers are easier to apply according to the gear makers I interviewed. They all seemed to prefer thinner sealers.
Thicker seam sealers are more difficult to apply, but they might be well-suited for specific applications. For example, in the above video Tarptent recommends painting stripes on your tent floor when the seam sealing solution is thickest.
If your brand-name silicone-based sealer is too thick, West has found that thinning it with mineral spirits makes it easier to brush on.
Special thanks to John West of Borah Gear, Whitney LaRuffa of Six Moon Designs, Henry Shires of Tarptent, Ron Bell of Mountain Laurel Designs, and Eloisa Townsend of Gear Aid for taking the time to answer my questions. Photos courtesy of Gear Aid.