-
- Juice bottle with a good squirt of all four food colors.
-
- A quirt each of yellow, green, blue and red make nice black water.
-
- So easy.
My cold frame does not have a hot bed (a layer of manure a few inches below the floor to create heat as it decays), and it only gets a few hours of sun at this early point in spring, so I wanted to add thermal mass.
Thermal mass is simply extra material that will be heated by the sun during the day and then will give off that heat after the sun goes down to maintain the warm temperature of the cold frame.
Online suggestions included painting milk jugs black and filling them with water. It was already night so I didn’t have time to paint jugs, plus if I painted my bottles and jugs I wouldn’t be able to recycle them later.
All I really needed was black water. It would absorb the heat better than the clear water and I could just pour it out when I’m done with the cold frame.
FOOD COLORING.
Every art class since kindergarten demonstrates that mixing all the colors makes black. I dug out my Target-brand food coloring left over from Christmas and got to it.
It worked like a charm – one good squirt of each color into each container made inky-black water perfectly suited to add thermal mass to the cold frame.
As I arranged them inside the cold frame itself, in the dark with a flashlight, I wrapped a few of the bottles in aluminum foil to help reflect the precious little sunlight that was making it into the cold frame in early March in our city back yard.
