Hi everyone,

What do you pack as transpiration bags and where do you get them? What are the desirable features like size, thickness... Should I buy clear garbage bags? What were the characteristics of Global Survival transpiration bags?

Thanks in advance
Frankie

Most garbage bags say "Not recommended for food storage". (Esp the ones with insecticide embedded in the plastic.) I am assuming that this would mean for water, too.

Other than large oven-cooking bags and food storage bags, what could you use?

Sue

Yeah good point. I forgot about it. I'll try Turkey size oven bags and see how it works.

Frankie

plastic has to be clear or else it won't work.

Oven bags for the kit, but the best I've found is (no body laugh) the bags presliced loaves of bread come in. Problem is, you generally don't carry those in your survival kit.

Clear plastic LARGE bin liners - 44gal size. You should be able to fit inside it. Oven bags and bread bags are just too small. A large bag might get you one litre per day if the bag is well sited and using the best hydrated tree. (Reference below, found 1.8 litre was max yield in study).These bags fold up to about the size of a paperback. Transpiration is driven by heat and light, so clear bags are best, whilst black bags are not advisable since they have a small yield and photosynthetic breakdown products (biodegradeable) are toxic, as well as any chemicals designed into the bag.

Maximise your yield by making sure:

1. The tree is non-toxic and the branch foliage will fill the bag.
2. The branch is (for N hemisphere) facing south to maximise solar collection (S hemisphere, face north).
3. The branch has a thick wrist around which you can effectively seal the bag.
4. You gather a small pouch in the bottom corner of the bag and tie a band around it to form a sump with a pinch above that keeps leaves and insects out of the water.
5. If you have it, tie your drinking tube down into the sump so you can drink without untying the bag. ( If you dont have a tube, cut a small slit on the seam of the bag at the top of the sump and keep it pinched closed with a split twig or tape it when not drinking.
6. Prepare the branch by trimming or padding any sharp twigs that might puncture your bag.
7. Don't anchor the bag corner to the ground. If the wind blows the bag tears and you lose not just the water but the use of the bag as well.

I'm sure someone else can explain the science of transpiration for us. As the atmosphere inside the bag increases the humidity and the temperature, leaf stomata open in response to this distress to increase the rate of transpiration and cool the leaves. The tree pumps more water to the branch. Water condenses and collects in your sump, until the atmosphere inside the bag is saturated with water vapour and this causes feedback to the stomata and shuts down the stomata, limiting yield. You drain the water to prevent this happening.

Leaves under this stress will eventually begin to break down and begin releasing natural oils and other irritants/toxins if the bag is left in place for too long. Survival trainers in Aus recommend moving the bag to a new location every day. The bag does not generate any water in the dark, so you can take it down and use it for something else overnight if you wish. Carry waterproof tape to repair any minor punctures.

Best of luck.
Reference: Kavanagh, B.L., 1984 - Survival Water in Australia's Arid Lands. The Strategic and Defence Studies Centre, Research School of Pacific Studies, The Australian National University, 1984

Check out these 60-gallon bags:
Survival and Outdoor Safety

Great info on changing the bags every night!

Thanks!

Thanks bones for the reply. Very good information.

Frankie