Re: How to safely turn clear water to black.

Hi Michael,

The only one taht comes to mind and it rather benign is the use of iodine 
and a bit of startch:

The resulting statch-iodine complex is black to blue-black:

I2 + starch --> a blue/black complex 

So means that you 'll have to add a bit of iodine to the water (can deg 
this at a drug store) and them sprinkle a bit of starch (magic dust).  
You'll probably play around with the amounts and concentrations.