Greenhouse: Greenhouse w/in a greenhouse to help heat (1st Winter), 1 by jlj072174

jlj072174 wrote:
I frequent a cafe by my office, and it paid off this week -- they gave me these Illy coffee cans with screw tops! I can think of a bunch of ways to use them, but first and foremost, my thoughts were to fill them with water to help heat the greenhouse in the winter as others have suggested (passive heat source). But I don't know that I want to have to paint them black for it to work. Do those of you who use the water/passive heat in your GH have all of the containers painted black? I realize it might be more absorbing of heat but wasn't sure how critical it was for this purpose/application.