All Jo's pieces are cast using the lost wax casting process. A visual breakdown of this process can be seen in Caroline’s repurposing story here. When repurposing a customer’s gold jewellery we give our casters the gold along with a wax model of the piece of jewellery it is to become. They create a sacrificial mould just for this new piece of jewellery from my wax model. The wax evaporates away in the mould making process leaving a perfect negative space for the customer’s gold (which is melted down) to be poured into. The mould is then broken away revealing the new gold cast.
It is worth noting that normally multiple pieces of jewellery are cast at the same time in one mould - often Jo's work will be cast alongside various other designers’ pieces. This reduces the overall production cost. This is not possible when repurposing personal gold which means the production cost for this process is quite a bit higher.