[tjwilhelm]

Nice Pics, B52! Experimentation is a wonderful thing! Thanks for sharing!

By the way, clear vs. black, Mac and Kevin are both right.

[Shep]

Let me save you all some time - black plastic, while in theory should work since black absorbs heat, turns out it doesn't work at all, so don't bet your life on it - you'll lose. Your experiments will prove out the truth of my statement.

The solar still with clear plastic works, but you'd need about 12 or more stills (depending on size) to supply one person's drinking needs, since 2-4 ounces maximum per day is about all you'll get - NOT practical, since it takes so much plastic and so much labor. Books say up to 1 qt. per day output from a solar still - but I have yet to meet anyone that ever got anywhere close to that amount. That oft repeated statement in books turns out to be a sort of urban legend, and is typical of survival guides that postulate instead of doing the "been there, done that" experience. Even those survival experts that demonstrate on camera how to make a solar still, often don't show you how much it produced. Good to know solar stills work, but there are better ways to obtain purified water with less labor, time spent, or materials.

[Craig]

That's a great experiment B52! You really learn so much more when you try it yourself. Can I make a suggestion: next time use a bucket instead of a cooking pan. The bucket is much deeper and of greater volume. You'll be able to increase the downward angle of your plastic into the catch container. Great point you made on the practicality of the still in an urban setting. When I made mine in the woods, we had to expend considerable resources (energy, water, time), but if you have most of the tools in your house already, I would imagine it takes just a few minutes to put together and requires very little effort.

[tjwilhelm]

Shep is right!

[B52gundog]

@Craig - Thanks for the tip. Coincidentally, I was trying it again today using the same materials except using tainted water instead of vegetation. I couldn't find a shallower catch cup so I tried to just have less angle on the plastic. No dice. The water condenses, but there's not enough angle for it to drip to the cup. It just drips back into the pan once a big enough drop forms.

I tried a bucket and an oil change basin (with painters tarp plastic and rubber bands), but had too much trouble getting a good seal around the top because of the indentation for pouring. The drops weren't forming as well as those in the pan.

From my perusing the internet on solar stills it seems the reason you want clear plastic is because its surface stays cool. This way the evaporated water vapor can condense on the cooler surface of the clear plastic. If the plastic were black then its surface doesn't stay as cool preventing condensation of water droplets to form against it. The black plastic will likely be the hottest part of the solar still absorbing the suns heat leaving the tainted water or vegetation to be cooler instead. Hence, minimizing the desired evaporation/ condensation process.

It's interesting as I briefly researched this cause some folks have gotten quite technical on measuring and explaining water output. Also, some good ideas on trying to improve output. Like, floating a dark material on the surface of the tainted water. So, rather than having to heat all the tainted water, only the surface gets heated so it can evaporate quicker.

Another idea I liked, was using a large Fresnel lens to boil the water using the sun and distilling it that way:

[LaRemnant]

Originally Posted by Shep

Good to know solar stills work, but there are better ways to obtain purified water with less labor, time spent, or materials.

Would you mind explaining a few examples? I am curious because I agree that solar stills are at best a last resort option, and I know a couple things on how to procure water, but I would really like to hear what you might have to say because I may not know it and therefore learn something new.