Isabel Farchy

Scoria is an igneous rock formed in volcanic eruptions. The word derives from the Latin ‘scōria’, meaning waste, dross or rust.

It’s defining feature is porosity. Scoria is the solidified, frothy lava which forms when it is violently ejected from an erupting volcano. It contains a multitude of holes.

A volcano erupts when a fracture in the earth’s crust means that hot lava and gasses escape. Deep down underground, the pressure is great, forcing the gasses to mix with the molten lava. As the mixture spurts out of the volcano, two things happen.

1. Because the pressure is reduced, gas and lava are no longer forced to mix, meaning tiny gas particles begin to find each other and form bubbles in the rock.

2. The frothy lava meets the air. It cools rapidly and the bubbles are frozen as the rock hardens.

My Experimentation

As part of my research, I have been experimenting with clay and glaze recipes. The addition of different organic compounds, silica, frit, bentonite, ilmenite etc. has various outcomes.

I ran many material experiments using different ingredients in varying proportions.

The final recipe contains*:

A black base glaze; Silica to cause the formation of bubbles; Borax Frit, a melting agent contributing to the glassy texture; Ilmenite (coarse) and Silicon Carbide, the combination of which cause iridescence; Porcelain, a cohesive agent; and Pearl Ash, an organic matter which, like sand, produced gasses when fired at high temperature, causing bubbles to form in the mixture.

*Amounts will remain undisclosed

Lightweight, glassy, strong, and porous, the material has the same properties as scoria, with some aesthetic differences such as iridescence and the option of varying colour.