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How to Waterproof a Black Diamond FirstLight Tent

The Black Diamond FirstLight Tent is a four-season, two-person tent that weighs 2 lbs 9 oz. It’s a single-wall, free-standing tent that is a snap to set up, which is important in freezing weather when you want to get out of your cold damp clothes and into warm dry ones. I’ve been using a FirstLight for nearly 10 years for winter backpacking and camping and haven’t come across any other tent that’s as lightweight and convenient to use.

But the FirstLight has always gotten a bum rap as not being waterproof, even though the fabrics it’s made with are. For example, the current FirstLight’s walls have a hydrostatic head of 1500 mm, while the floor is rated at 3000 mm. That’s is more waterproof than many of the mainstream backpacking or camping tents sold today.

The part of the FirstLight that is not waterproof are the seams, which need to be sealed if you need to use the tent in the rain. Whenever you sew two fabrics together, you create many needle holes and that can leak water when it rains. These seams can be factory seam-taped on conventional tents that are coated with polyurethane, but you can’t seam tape tent walls that are made with silicone-impregnated fabric, like those on the FirstLight. These need to be filled with silicone seam-sealer which can bond with the silicone-impregnated walls. That’s why Black Diamond includes a tube of silicone tent sealer in every new Firstlight tent.

Assemble the materials you need for the seam sealing process

The first step in the seam sealing process is to gather together the materials you need:

  • Silicone tent sealant (1 tube comes with the FirstLight at purchase)
  • 1″ wide foam brush (much easier to work with than the brush included with the seam sealer)
  • Paint thinner (a paint thinner substitute or white gas will also work)
  • Mixing can (a tunafish or catfood can work well)

Caution: Seam sealing should be done is a very well ventilated location, preferably outdoors. When you are finished, you’ll want to let your tent or tarp dry for 24-48 hours. 

Squeeze the silicone sealant into the can and dilute it about 50/50 with paint thinner. Mix well. The paint thinner will thin the silicone sealant so it seeps into the needle holes more readily than undiluted silicone sealant. When mixed, wet the tip of the foam brush and run it slowly along all the exterior, exposed seams on the FirstLight Tent. This includes the seams where thread stitching is visible and where it’s not. There’s no need to seam seal the corners of the bathtub floor since these have been factory seam-taped on the latest FirstLight model.

Brush the silicone mixture onto the seams and let it soak in

Places where you want to focus your attention, are:

  • the roof
  • sidewalls, under the arched poles
  • peaks above the front doors and rear window
  • the seam between the sidewalls and the bathtub floor

If the mixture begins to thicken as the solvent evaporates, you can add more and mix it in. If you apply a little extra to the fabric on either side of the seam, that’s ok too. Seam sealing isn’t a surgically precise process although you want to avoid making a mess. The entire process should take well under an hour.

Seam seal the seams over the arched poles and around the rear window beak

When you’re finished, carefully inspect all the seams and touch up any spots you missed. Then let the tent dry for 24-48 hours, before packing it away or using it in the field.

Once you’ve seam-sealed the FirstLight, it is will be fully waterproof and should remain so for the effective life of the tent.

Disclosure: Black Diamond gave the author this tent for a future review.

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10 comments

  1. Why doesn’t BD do this before shipping?

    • Tarptent, Six Moon Designs, Mountain Laurel Designs…they all push this task onto consumers. Why? To reduce their manufacturing cost.

      Why doesn’t BD just make this tent out of a PU coated fabric so it can be taped? You’ll have to ask them.

  2. In this day and age why would ANYBODY want a SP Tent that is so small and so darnn heavy. 2 lb, 9 Oz…….Geez…..My tents are: Duplex 19.42 Oz…Lunar Solo 24 Oz… SW Tarptent Moment 28 Oz and my Lanshan 2 is a whopping 39 Oz…….. Hi Philip ! 8-)

    • Because it’s a winter tent and far less drafty than the tents you list. Those are really cold tents to sleep in winter, with the mesh between the walls and the ceiling. You couldn’t pay me to use them. It’s also fully freestanding, so you don’t have to stake it out, and wait for your tent stakes to freeze in place so your tent won’t fall down.

  3. I love that I can insert the poles into the tent without having to get inside, myself. You just pop one end of a pole into its pocket at a far corner, push it up and into its near corner. Do that twice, from the outslde entrance, and you will not get any serious weather into the tent.

    Then toss in your gear – all of it – and have yourself a cozy winter nest with room enough to hold all your gear at hand.

  4. Stephen Van Voorhies

    What was the old Bibbler tent made of, wasn’t it breathable as well?

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