Sunday, December 18, 2022

Guest Post: Waterproofing a Bivy Cover

 by George Groot

George is a member of our Facebook Group and has written for us before.

In the late 1990s I turned in my old olive drab canvas sleeping bag and received a new issue of the Army Modular Sleep System (MSS), which consists of a lightweight summer sleeping bag, a heavier winter bag, and a Gore-tex fabric bivouac (aka bivy) cover. All three items snap together to make a single unit, but you can mix and match the bags as needed; one time I even slept in just the bivy cover during a Texas summer. That old MSS set in woodland camo was turned in years ago as the Army transitioned to the “Let's invade the Moon!” Universal Camouflage Pattern (UCP) before transitioning to the current Operational Camouflage Pattern that looks very similar to MultiCam.

On the surplus market you can find all the parts for an MSS in both woodland and UCP camouflage patters, but for this article I just want to talk about the bivy cover. Generally this is the most expensive part of the MSS since it is made of Gore-Tex, which is generally a dandy fabric for the great outdoors. However -- and I’ve learned this the hard way -- Gore-Tex does not retain its waterproof capability after being run through the washer/dryer in order to get your gear clean for Central Issue Facility (CIF) turn-in. This means that a lot of the bivy covers on the surplus market aren’t very waterproof at all.

However, that doesn’t mean they can’t be made useful again. I recently purchased two UCP pattern bivy covers for my sons, and paired them with a Walmart-brand mummy bag for camping with their Trail Life troop. However, my eldest son woke up in a puddle of water while still inside the tent his first time out. This was a failure of both tent site selection and of the bivy cover, as it offered no protection from the water seeping into the tent. Since the poor judgement of my children isn’t the topic of this article, we’ll focus on getting the bivy cover back up to shape.

Gore-Tex from the factory has a “durable water repellant” (DWR) applied to the fibers. If your bivy cover easily accepts water rather than having water bead off, then it’s likely you need to re-apply a coating or two. The three main types of DWR are fluorocarbon-based, silicone-based, and hydrocarbon-based polymers, and they come in both wash-in and application varieties. There are a lot of “nano-tech” products on the market now, many advertised as “silicone free” but from the reviews I’ve researched and the single product I tested, they come with mixed results.

Wash-in is likely the easiest method, as it lets the washing mashing do all the work. This will generally apply the DWR evenly, inside and out. For something like a bivy cover this should be just fine, but for something like a Gore-Tex jacket with a sewn-in liner, it may not be the best choice as it may change the ability of the liner to wick moisture.

Application, either spritz on or spray on, has the benefit of being a readily available option in most big box stores and sporting goods stores. You’ll see these as various offerings from Scotchguard and Sno-Seal in most chain stores, and specialty stores may also carry NikWax.

However you treat your surplus bivy cover, understand that it isn't waterproof any more, only water repellant now, but just like older canvas bivouac covers it is still an incredible value-add if you have to camp without a tent. If you also have cotton bivy covers, then there are a lot of wax-based fabric treatment options that can really help increase the water resistance, some cheaper than others. (Erin wrote about waterproofing cotton with wax in this article.)

What I did to pep up my son's bivy cover was to spray the outside with Tex-10 water repellent, which turned out to be really expensive and didn’t give the results I wanted. It was difficult to get an even spread/penetration with the spritzer, and so the next day some areas beaded water beautifully, while other areas soaked up water like a sponge. It's not a great value for the performance, so I can’t recommend it. 

For a second treatment I turned the bivy covers inside-out, liberally sprayed them with an Atsko Silicone Water-Guard from Walmart, and let them dry hanging outside overnight. The next morning I tossed them into the dryer and tumbled them on low heat for 20 minutes, and the results were much, much better. The organic solvent provided much easier product distribution through the fabric than the water solvent of the Tex-10, and while the environment might take a hit, better performance for 25% of the price seems like a good thing for us blue collar types.

If I have to do this again, I’ll probably plan ahead and order a NikWax wash-in product, as they have the most consistently positive reviews for treating hard use outdoor gear. NikWax products are also beeswax-based, for those who might prefer that over silicone. 

None of these treatments last forever, so you will end up re-applying as needed to keep performance at an acceptable level. In Alaska that’s probably going to be more often than Arizona or North Carolina.

Stay dry!

No comments:

Post a Comment

The Fine Print

This work is licensed under a Creative Commons Attribution- Noncommercial- No Derivative Works 3.0 License.

Creative Commons License

Erin Palette is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to