Where can I find a/an (ideally black) watertight fabric that could be used for a solar water heater?
The idea is to sew several tubes into watertight fabric in a design like a radiator, and then fill them full of water. The idea is that this will absorb the heat from the sun and then, as night falls, act as insulation against the cold. And I am hoping that I could hang them in the windows of my house and remove them when it warms up.
Does anyone have a suggestion for watertight fabric that I could use for such a project?