Fired Cast Slate

Culture & Context

I used slate from a local quarry in Valentia Island, Ireland.

Valentia slate has many notable historic applications in and outside of Ireland, and holds significance when doing a deep dive into traditional Irish materials, and Irish material culture. 

This material was an attempt to work with slate in a new and contemporary way, bringing a breath of fresh air to how designers can work with locally sourced stone.

Process & Production

Wear a dust mask while handing slate dust, wear gloves when handling sodium silicate.

Recipe Details

Air dry cast slate:

• Collect slate silt.
• Rinse silt with clean water.
• Dry silt to remove moisture, preferably in an oven, until it is a dry powder.
• Sift powder to break up clumps, achieve uniform consistency.
• Measurements by weight: 70% slate, 15% water, 15% sodium silicate. (experimentation + samples is recomended)
• Combine water and sodium silicate, mix well.
• Combine the diluted sodium silicate with the slate powder.
• Mix thoroughly to remove clumps. 
• Add mix to non-porous mold. (porous molds will extract the water and sodium silicate from mixture and intervene with bonding process, resulting in a crumbly product)
• Let dry for at least 48hrs. (Drying time depends on the size of casted piece, drying time could take up to 2 weeks or more for larger pieces or pieces with little exposed surface while in mold. CO2 improves the hardening process, and accelerates drying time. Otherwise, use a drybox, with a fan and dehumidifier. The goal is to remove all the water from the solution, and allow the sodium silicate to bond all the slate together)
• Fire in kiln. (my samples were fired at 1000 degrees for 30 hours) 
• I wasnt able to experiment with glazes, but various ceramists told me that it shouldn’t be an issue.