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.
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.
1. Structural – lightweight concrete
2. Abrasive – skin exfoliation, toothpaste, industrial polish
4. Agricultural – ground cover that supports drainage, part of the soil mixture that supports oxygenation, or in soil-less, hydroponic systems
Note, because of the way they are ejected at high speed from the volcano, scoria form in small pieces, or ‘lapilli’, which litter the area surrounding volcanoes. Their small size, limits they application. But what if you could make larger lumps of scoria?
Note, scoria’s useful properties mean it is already artificially produced. The man made version is called Expanded Clay.
Organic material is fed into kilns. The moisture in the clay produces gas which creates bubbles, as those found in scoria.
However, as it’s fired, the organic matter tends to fuse to itself. Rotating kilns are used to prevent this. The resulting pellets are smooth on the outside and the porous structure shows only when you break it apart. A shame?
I make the objects by pouring the mixture into a bisque fired, clay vessel and firing it at 1260°c. Once fired, I chip away the clay to reveal the porous surface of the material.
2 Living Wall Panels
3 Sound Insulation Panels (interiors)
3 Sound Attenuating Sculpture at Heathrow! (exterior landscapes)