[freerpg]

ok so my first post so please be kind
I am hoping to find a chemical in powder form that reacts as follows
when additive A (liquid) is added it has the texture of a soft rubber or hardens to at least strength of plastic (acrylic) depending on quantity added
resulting compound will stick to previous layers
safe for humans to use (ie not poisonous corrosive etc)
and if I add standard inks to it, it can be coloured whilst keeping its density.

does this exist?

[Enthalpy]

Dyes for polymers are used in minute amounts so they will keep the density.

Fine, I've done my part, other forum members shall answer the powder-to-rubber-to-hard plastic part. 

Joke besides, the same compound being a rubber or a hard plastic, that's not common. Presently I think only of latex which becomes soft rubber with a bit of sulphur (vulcanization), or becomes hard rubber with much sulphur. "Hard rubber" is really hard, it makes clarinet mouthpieces for instance.
http://en.wikipedia.org/wiki/Vulcanization
Silicone never gets hard. I can't tell for polychloroprene.

You probably ask too much. A rubber or a thermosettig polymer depending on the intensity of cross-linking does exist; I'm not sure you can choose the colour (or at leat, the palette is limited), and demanding a liquid and a powder initially (latex and sulphur) is probably too much, full safety as well. Rubber from latex fits more or less by chance, but would there be others?

[freerpg]

ok so what if I change this up a little
I add to powder liquid A making it rubber like
I add to powder liquid B making it rigid
I add a mix of A and B making it somewhere in between depending on ratio

the idea is the basis for 3d printing using powder. the powder acts as the support material and the end products walls.
I was also thinking of making a powder mix of 2 separate powders that react with 2 liquids so it would go as follows
powder A mixes with liquid A
powder B reacts with Liquid B
powder B and liquid B does not react with either Liquid A or powder A.
however adding mix of both liquid A and B will allow something between rigid and rubber like
colours can be added

[Enthalpy]

Does it need to be a chemical reaction between the powder and the liquid?

For instance, Pmma powder could be impregnated at will with Mma (or rather an oligomer if possible because Mma is nasty), exposure to light would make solid Pmma where Mma was added and leave powder alsewhere.

As opposed to early 3D printing machines, the Mma drops would define the shape, not the selective irradiation. And you'd get a versatile plastic: transparent, accepts dyes, etc (but brittle).

Maybe an elastomer loaded with Pmma powder is acceptable?