View Full Version : Bivy and Silica Gel?

Time Zone
10-29-2016, 00:09
Would the use of silica gel* (say in a sock at the foot end of the bivy) be safe and effective at reducing or eliminating condensation in bivies? Assume your bag isn't excessively warm, but that you are zipped up with just bug netting over your face, or your face and upper half.

I'm just not sure how safe it would be. You're not supposed to breathe the dust, but there appears to be very little dust with this stuff anyway. It's not like clumping cat litter (though it is sometimes used as cat litter - in fact, it's a good way to buy silica gel in bulk).

I don't think it would be practical for multi-day use, since you probably wouldn't have much of a chance to dry it out (and if you did, maybe you'd just dry out the bivy/bag instead, right?). It would add several ounces too, and then weigh even more after absorbing moisture. Still wondering if it would be of any use at all. Seems like the only solutions to avoid moisture is to do away with the WP/B aspect and either have a mostly-netting top, or something that is only water-resistant.

Just one of those curious people thinking of whether/how a WP/B bivy could be made to work ... in the southeast US.

* named "gel", but looks like beads.

10-29-2016, 01:25
Never considered it. I so very much like and appreciate being presented with new perspectives. Worth a try. I have loads of silica gel packets found in vitamin bottles. I will try it.

With my WP bivies I prefer not being zipped up entirely preferring to have the hood slightly overlapping and above my head via a stiffener hood loop or overhead guyout. Site location is important. Breathe(moisture vapor) is exhaled easily to the outside. I tend to use WP bivies in the cooler seasons. I'm wearing dry clothes and rain jacket and maybe rain pants to trap insensible body moisture. I may pare with a synthetic quilt/sleeping bag or use a down bag with a protective shell and/or wear VBL clothing.

My preferred go to WP bivy is the MLD Soul eVent. http://www.mountainlaureldesigns.com/shop/product_info.php?cPath=22&products_id=173



With expected heavy daily rain on multi day outings in warmer weather I prefer a tent or WR MLD Superlight bivy with a cuben tarp. I also have used both the Titanium Goat Ptarmigan and Raven Omni WR bivies under tarps with good experiences.




Mountain Mike
10-29-2016, 01:41
I don't see where it would be worth the weight. I've owned & used several bivy sacks. Rainy southeast isn't where I would use one as a primary shelter. Just getting into one on a rainy day would pretty much defeat purpose of the silica. I think you would be better off with a small tarp.

Cottage industry tents are getting so lightweight now that weight saved by using a bivy, especially if you need a tarp with it is almost impossible. Cost of a decent bivy & light weight tarp are offen exceed price & weight of a tent. I mostly use mine in winter or dry climates where rain isn't likely.

Leo L.
10-29-2016, 05:06
Up to my opinion, there is no sense in using silica gel.
Even if the gel is able to take a reasonable amount of moisture from the air volume inside your bivy (which I doubt because you dont have free air flow inside the bivy an the gel pack might be tangeled in a corner of the bivy, thus being sealed away), next morning there is no way to get the water out of the silica gel. Unless you take the task of heating it up in a proper way, which would take time and fuel and some additional stuff (kind of a baking oven).
So you would end up with lots of stuff to carry and lots of work to be done just for to get rid of some moisture, whe you basically just wanted to hike and have fun. Poor trade, IMHO.

The only way silica gel could help for hiking/surviving is to gain water from the air in an otherwise dry area, when you carry and can use a solar heater. Nothing for hiking, but more for expedition use.
This was tested in the Danakil desert and found to make some reason by a German guy, nicknamed "SirVival" (his full name is Ruediger Nehberg).

10-29-2016, 11:04
You'd probably need a couple pounds of the stuff to have any effect what so ever.

10-29-2016, 11:26
Silica gel is a dessicant.
There are super-adsorbent polymers that hold more moisture.
Think the stuff in baby diapers

Some is even marketed and used for keeping humidity constant in storage applications for things like instruments, antiques, etc. It absorbs and desorbs moisture from air in enclosures to buffer damaging changes.

Still not a viable idea for a bivy. People give off way too much moisture. Youd need a few lbs of stuff and good circulation to handle the rapid rate of water produced by a body in closed space.

Time Zone
10-29-2016, 12:12
Thanks, all. I didn't realize that to dry out the silica gel again you would actually have to heat it to dry it out. I thought maybe if you put it in a really dry house in winter, say, it would naturally dry out. Anyway, w/r/t ultralight tents and tarptents and so forth, yes, they are pretty amazingly light. I already have a bivy and tarp (both Kelty, incidentally), and although they're not ultralight, they were inexpensive and appear durable. The bivy itself has something like 21 sf in a nice rectangle, and can be staked out.

At the moment where I am we are in an exceptional drought - the highest level assigned by the drought monitor organization(s). So I'm not terribly concerned about the rainy southeast at the moment (plus I have the tarp) - however, it is still very humid at night, and of course the body gives off quite a bit of moisture no matter how dry the ambient air. So managing it in a WP/B bivy is always an issue I think. I know that "cesar and the woods" cut into his bivy and extended the mesh toward the feet and it made a huge difference. Perhaps someday I'll do that, but I definitely hesitate b/c that's an irreversible mod!

10-29-2016, 13:49
A bivy is just another tool a shelter option to have within your shelter quiver. They are worth considering for use within the hands of those who understand their design applications, specific user's conditions, and individual goals.

There's a lot of valuable bivy info in those links provided if it will be considered and assimilated.

There certainly are WP and WR bivies whether used in stand alone fashion(hooped or unhooped) or in unison with a tarp that rival quite nicely with the wt of the most UL tents. For example, my goto MLD WP eVent bivy in large size with my own plastic hood stiffener weighs 15.2 ozs. And, the lightest wt UL tents are not cheap and bivies are not always all that comparatively expensive. Here is Ryan Jordan's review of the MLD eVent Soul bivy: https://backpackinglight.com/mld-soul-bivy-review-jordan/#.U2o1H-DUPGs I know of WP bivies that weigh less! Here are some wts of various WP bivies accumulated by world experienced adventurer and bivyer Tim Moss who has used a bivy extensively in a variety of situations including the rainy UK and rainy season Korea:http://thenextchallenge.org/comparison-best-bivi-bags/ There are links in there to several articles and books that every budding bivyer should assimilate that wants to advance in their bivy use, including topics of condensation. I highly recommend Ronald Turnbull's Book of the Bivy and this http://thenextchallenge.org/how-to-bivouac/

As I have, you might also get some insight from Rob Reaser's The Bivouac Handbook(A No Nonsense Guide to Austere Wilderness Camping) https://www.amazon.co.uk/Bivouac-Handbook-No-Nonsense-Austere-Wildnerness-ebook/dp/B008ACMN14/ref=pd_sim_351_3?_encoding=UTF8&psc=1&refRID=7NPWZ0THZS1JG8MSDEK2

For anyone serious about using a bivy do you think it pays to give greater heed to those that do it extensively? There is a lot of misunderstanding especially within the camping as usual U.S. hiking community concerning bivy use and no less so than on forums like WhiteBlaze! NO, you don't have to drown in your own sweat or from condensation or experience a coffin like bivy experience! And, as amply noted bivies can be employed effectively in wet conditions too!

One of the greatest aspects of a bivy, beyond all the negativity, often pointed out quickly by those who have little to no experience in a range of conditions employing various bivies, is the minimalist footprint that has allowed me to sleep atop summits, narrow ledges, ridges, at the base of waterfalls, in caves, in choked temperate understory forests, between rocks, etc where no tent could be erected. This has led me to experience things I would not otherwise been able. Turnbull's book cover gives a prime example.