Black Dye for solar gain in water?
I remember reading some posts a while back where people were talking about solar gain for things like water bottles, etc.
In the past, I've always spray painted the bottles flat black, but somebody mentioned that they thought you could gain just as much heat by dying the water black instead of painting the bottles. I have a bunch of saved fruit juice containers, and want to put them in my cold frame and row cover and thought I'd try the dye method, but I'm not sure what type of dye to use.
Obviously, I'd be looking for something that doesn't "settle" at all, and stays suspended in the water. Anybody have any recommendations?