Celfoam

Celestial foam, usually shortened as celfoam, was a “multi-purpose non-substance”, created by “beating spatial dimensions with an egg-whisk according to a very particular pattern”.

The clouds in the Cupid Homeworld were made of celfoam. As such, they were simultaneously weightless and able to support the weight of people walking on them. The outer coatings of Fog Ships were also made of celfoam, hence their name and the fact that they were maintained by the Celestial Foam Network; this was an example of a more sophisticated use of the dimensional properties of celfoam, (PROSE: The Crew of the Copper-Colored Cupids) allowing the Ship to phase through the dimensional barriers between worlds. (COMIC: The Beginner's Guide to Multiversal Theory)