Solar Still with Oven Bag

W

wade

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Sep 22, 2005
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Anyone ever tried using a Renolds Oven bag tied around a tree limb? Would that material work ok? Who wants to experiment with this for me and tell me how well or not so well it actually works. I have seen this method in almost every outdoor survival book but never tried it. I am wondering if it is even worth making, but my water bag in my PSK is a Renolds oven bag, so if it does work that would be cool.
Wade
 
In my experience it takes something more the size of a garbage bag to get a usable amount of water. At least with the climate and vegetation in the areas where I have tried transpiration bags. FWIW I too keep a large Reynolds oven bag in my PSK as a water bag. They do make outstanding water bags.
 
Well right now I am in an apartment and dont have a yard to play in so I was wondering if someone would do this experiment for me. Tie a oven bag over a limb and see how effective it is or is not. Thanks
Wade
 
Hmmm. That would require that strange light in the sky that went away in October. We're solarly-challenged. :(

(I've always used big honking bags - 30 gl.)
 
IMO you can't use a large enough bag for this. Only clear bags work well for transpiration and the more leaves you can get in the bag the better. When I did this in dry season I got about 25 ml of water from the bagged branch. At that rate I'd have to hang a few dozen bags to get a canteen full of water.

http://img221.imageshack.us/my.php?image=stbaggedbranch6dg.jpg

On the same trip I used the same sized bag to build a solar still in the ground. That produced another 25 ml of water or so (I'm working from memory here).

http://img221.imageshack.us/my.php?image=stsolarstill14cx.jpg

I also stuffed a bag with green leaves and left it to distill in the sun. That also produced about 25 ml of water. It seemed to me that the bags just baked the water out of the leaves. This water was collected from the bag stuffed with leaves. I transferred the water to a smaller bag for the photo.

http://img215.imageshack.us/my.php?image=stplantwater2bm.jpg

The first morning there was a heavy dew on the ground. I was able to collect almost a full liter of water in about an hour. By far this was the most effective use of my resources.

http://img215.imageshack.us/my.php?image=stdewcollection1vu.jpg

This is the water collected from dew. The clearer looking water came off my tent. The brownish water was collected from grass.

http://img216.imageshack.us/my.php?image=stdewwater5ux.jpg

On another trip to the same place at about the same time of year I was able to pull a few hundred ml. of water from a boulder using a 60 ml syringe and plastic tube. This water had a very earthy taste and needed to be filtered and heavily treated with iodine.

http://img69.imageshack.us/my.php?image=60mlrockwater1mf.jpg

My purpose in this experiment was to see which field expediant method gave the best results with the same resources. By far dew collection was the best strategy. I could not have survived on the water collected from the various plastic bag techniques without having enough bags to equal the weight of an extra canteen. Digging a solar still in the ground cost more in sweat than it produced. You can argue that my still was too small and not banked enough for steady drainage. I'll accept that criticism, but I won't bother with them again unless it is to prove the point I'm making here.

The 60 ml syringe is worth it's weight in gold as a tool for extracting water from a demanding landscape. If I were to pack a survival kit with water collection as a priority I would include an absorbent cloth and 60 ml syringe before bothering to add enough plastic bags to make it work. YMMV depending on location. Mac
 
Mac,
That is what I wanted to know. I only pack one oven bag and I think that it is smaller than the ones you were using so I dont think it will work too good. Thanks for the picts and info.
Wade
 
Wade,

That's the serious fallacy with some of these methods. They work in that they do produce water but we're talking capfuls. The transpiration bags need to be HUGE and you need several of them on really lush vegitation to get "hydration quantities" of water. A solar still in the ground needs to be HUGE and dug over moist soil with steeply banked sides. They just don't produce the copious amounts of water you need in my experience.

I haven't tried to make one of the above ground, tent-type solar stills with a large sheet of plastic. At least if you could avoid the digging it would pay for itself in sweat. Mac
 
pict said:
A solar still in the ground needs to be HUGE and dug over moist soil with steeply banked sides.
Click to expand...

Have you checked the efficiency rate for recycling urine and other non-drinkables like salt water? You can check transpiration assuming 100% efficiency by just weighing vegetation then drying it out and weighting it. Unless it is really soggy with water like melons, it takes massive amounts as water is really dense and leaves don't weigh much at all.

-Cliff
 
nice post pict. collecting morning dew for a water source works very well indeed. any source for the syringe??
 
Grobe,

I buy mine in the "Area Hospitalar" downtown. That's the advantage of living in a city of four million. Doctors get their own neighborhood and have all their supply shops on the same street. I can get plastic tubes, surgical rubber, scalpel blades, etc. One stop shopping.

Check vet or farm supply places for the really big 60 ml syringes. I hear that ranchers do terrible, unmentionable things to cattle with them.

Cliff,

Once I pee I'm all done with it. I haven't gotten that desperate yet. I did read a post on Bushcrafters UK where a guy had distilled urine in the desert by actually making a boiler/condenser.

I want to dig a solar still on a beach the next time I go. Lots of sunshine, wet sand, refill underneath with seawater etc. It might be a profitable technique for seacoast survival. Prefab, inflatable, floating solar stills are standard in lots of liferafts but you fill the bottom with seawater as your source of moisture.

Down here we have green coconuts, yummy. The last time I did a "survival beach comb" up in Fortaleza they were a prime target, 400 ml of perfection. Mac
 
pict said:
Once I pee I'm all done with it.
Click to expand...

Not really, any water you drink was someone's urine once. It evaporates, comes back down as rain. I was just curious about the percentage turnover. Most who reference stills note it, but never talk about how much water is recovered. Everything is frozen here now, might try it later in the spring.

-Cliff
 
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