The Negative Space II

The simplicity of these forms is intentional, as mentioned in my previous post; there is much to consider. The most pressing relates to the materials with which to give concrete form to the negative, inner space, the 'open' space. They are many, but I feel I want to start with polyurethane foam. A material I like working with (click on Polyurethane Foam under Series/Themes on the right on the screen or click here Polyurethane Foam): I like the conversation it imposes. It continues to expand once it's sprayed, in its own, fairly unpredictable way, so, ' ... I talk to it, it talks back to me, and I respond, and so the conversation continues ...' (14/11/2016).

Of course its unpredictabilty will make things 'interesting', so we will have to see whether it works out. The foam will fill the open space and push into and out of the outlets, creating, I would think, interesting shapes as it protrudes from the inner space to the outside.
And where does that 'outside' space end?
And how will I extract the foam form from the clay form? Will I need, or indeed will I be prepared to cut it?

As I said in my previous post, I kept the first form simple, and did so because I wanted to limit the technical challenges (as mentioned above) to start with. 

Form I - one large inner space with four points of exit:

Form II - two large inner spaces, encountering the outer space in opposite directions. How?

Very many questions ...