It would be a pasty white color (rgb:228, 229, 227).
The description would be: Foam, expands when heated.
When heated, it will grow at a rate equal to the heat (50C, grows 10px, etc.).
Foam can't be melted or set on fire.
When put under very low or very high pressure, it will shrink (possibly).
It will not conduct electricity and acts as insl.
When touching an element, it will stick to it.
It also sticks to other particles of foam (they would clump together, only if one particle is stationary) (possibly).
That reply has nothing to do with this thread.
Hey, finally a good idea! (to me) MERC is annoying since it disappears when a big hump of it is placed down, breaking most of my saves. And GEL-like stick might be used to make better "Floating islands" or some stuff since it can grow/shrink and also stick, and it will fit nicely into the Powder/Liquid category. The non-flammable and non-melt can promise a LOT of new saves. Sounds pretty good to me, at least.