Density

The density of a material translates directly into the voussoirs’ weight, a very important role in stereotomic structures. Remembering Perrault (1697, p. 171) this is “the art of using the weight of stone against itself so as to hold it up thanks to the very weight that pulls it down”. Stereotomy would not happen in a zero gravity environment, nor with lighter than air materials. Actually, very light materials are able to perform stereotomically, as seen in the RDM Vault (McGee et al., 2013), or CorkVault Aarhus (Azambuja Varela and Merritt, 2016), but these are experimental pavilions; if someone would push a keystone from below with a broom stick, the whole structure could easily crumble down. The main reason for high density in stereotomy is the resistance to additional horizontal forces such as wind or earthquakes.