A friend of mine and I just finished teaching a 2-day Wilderness Survival course for a group of St. John Ambulance cadets, aged 11 to 16. Part of the course involved demonstrating various ways to collect water in the wild. <br><br>We had some success with a clear plastic garbage bag draped over a small deciduous bush, about 3 feet high. I tried to demonstrate a solar still using a green plastic garbage bag (slit down one side and along the bottom). I reasoned (never having made one before) that the green would absorb the sun's heat and increase evaporation from the soil underneath.<br><br>Part of the problem was that we didn't check it until almost noon the next day; I wanted to make sure that the cadets at least saw what it looked like before I took it apart. There was some condensation in the metal pan but nothing that I would call "drinking water". <br><br>Would clear plastic work better? Did I just wait too long?<br><br>None of the survival manuals I have says anything about what type of plastic to use. Two days after we returned, I was in Mountain Equipment Co-op and I saw a new survival blanket from Adventure Medical Kits. This one is 5' x 8' and is bright orange on one side; the orange side has survival and first aid tips/instructions printed on it, so it serves triple duty. The survival instructions say you can use it (the space blanket) to build a solar still, so it would appear that being transparent is not a requirement, although I would suspect you still need to build it with the orange (non-shiny) side up.<br><br>Any advice on what we did wrong? Does anyone have a list of common mistakes made when building a solar still?<br><br>On a related note - it seems to me that it would be fairly easy to build a simple distillation apparatus out of a cup and a Zip-lock bag. Fill the cup with contaminated or salt water, put a funnel over it upside-down, place the assembly inside the ziplock bag and seal it. The sun's heat should cause the water to evaporate, and the funnel would prevent it from going back into the cup when it condenses later. I haven't tried this yet; does it make sense?<br><br>Thanks in advance, btw; this stuff is fascinating.<br><br>