To make the gypsum mortar, it had to be dehydrated by heating which requires large quantities of wood.

The outer walls were massive, due to the ancient Mesopotamian tradition of using rubble and gypsum mortar for heavy construction.

Gypsum mortar was essentially a mixture of plaster and sand and was quite soft.

Gypsum blocks are typically laid in a compatible gypsum mortar or adhesive, then covered with a coat of finish plaster.

The father, Rafael Guastavino, innovated with the use of Portland cement as the mortar, rather than the traditional lime and gypsum mortars, which allowed mild steel bar to be used to counteract tension forces.

The core of the pyramid was built with the same technique as the main pyramid and the cult pyramid, consisting of three horizontal layers of roughly hewn local limestone blocks and gypsum mortar.

It is one of the oldest known types of mortar, dating back to the 4th century BC and widely used in Ancient Rome and Greece, when it largely replaced the clay and gypsum mortars common to Ancient Egyptian construction.