[Packrat79]

  Hi, I'm not sure if this is the right place for this but maybe you can help me out. I'm trying to create colored blocks of ice for a winter project but having mixed results. My first attempt was food coloring and water, but to my surprise the food coloring was compressed to a small puddle on the bottom leaving the ice perfectly transparent. My next attempt was printer ink and water, which produced very similar results. I then tried Tintex (powdered) fabric dye and water, this yielded much better results but still not as uniform as I would like. It also left a thin layer of unfrozen water and dye on the surface, making the block messy to handle.
  I admit I don't know much about chemistry but I suspect the base ingredients in the coloring is the problem, as most are substances that do not freeze. The food coloring contains a base of citric acid and sodium benzoate, the printer ink doesn't specify the contents but probably contains ethylene glycol, and the fabric dye contains salts. Does anyone know of a way to neutralize or remove these base ingredients so that these mixtures can completely freeze, and perhaps be more uniform?
  Thanks for any advice.

[Borek]

In a way you have just discovered one of the purification/separation methods used in chemistry - when you crystalize out one component from the mixture, others accumulate in the liquid left. This is expected (but I am not ready to try to explain the thermodynamics behind to a layman on a Saturday evening )

Sadly, it won't be easy to overcome. I would try to stir the solution while freezing (slight chance to trap droplets of the liquid with the dye in the ice structure) and to use pigment based (insoluble) dyes. Getting a crystal clear, colored ice can be impossible.

[Corribus]

One way may be to freeze the mixture more quickly. Think liquid nitrogen.