WHAT INSIDE a metal door (polyurethane, polystyrene, honeycomb, mineral core)

There’s typically 1 to 5 materials inside of a metal door. Polyurethane, polystyrene, cardboard honeycomb, mineral core, or just steel for reinforcement. They all have different properties and we talk about some of those characteristics in this video.

[@Greatwhitesloth]

I can't figure out what the mineral core is exactly.

[@Greatwhitesloth]

nvm I think it's magnesium oxide