"How to make polyurethane buildings? " Topic

Was just looking at the Vatican Enterprises/old Hudson & Allen foam buildings. I just wondered how that is done? Some type of vacuum form mold?

i think ther were injection moulded in foam or something similar

No, the polyurethane has two liquid components, one of which contains a foaming agent. When you mix them in the correct proportions the reaction produces a gas which creates the bubbles that form the foam. The material is essentially the same as solid polyurethane resin, just with bubbles. Like Aero, but less minty.

You mix the components, pour the mixture into a mould before it begins to rise, and clamp it shut. The foam rises, fills the mould and cures. Then its a matter of de-moulding and starting again. You can vent the mould, which lowers the density of finishes casting, but any excess will squirt out. Very sticky, very messy…

i think i will have to try that method in one of my old building moulds

Here is a nice video of how to cast with foaming polyurethane resin: YouTube link
The people who make props or fake props can provide a lot of insight on making things in molds.

Thanks for the info gents!