I think that the solar still deserves a good scientific test. So, this summer/spring, I believe I'll be digging a few holes in the backyard ('s OK, some idiot did a 720 degree turn back there in the last ice storm and killed off half the grass).

Parameters:

1) Air and ground temperature
2) Time to dig
3) Soil composition (read: clay)
4) Additives (vegetation)
5) Water collected (over time)
6) Plastic used
7) Amount of daylight

Am I missing anything? I'd like this to be definitive.
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Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, a critter that can be killed but can't be tamed. --Robert A. Heinlein