Nerikomi is a complex technique that take time and has many stages. The first stage is to prepare a range of coloured porcelains. The colours are added with ceramic stains and metal oxides, these are carefully blended into the soft porcelain. The coloured porcelains are then layered together to form a block, taking care to avoid incorporating air bubbles and making sure the colours are well joined to each other. You have to imagine the pattern inside the block and control the shapes although you cannot fully see what you have made until you slice the block.
It is necessary to rest the block once you have made it so that it can equalise moisture and consolidate as one piece of clay rather than many small pieces. Once the block is ready (around a week later) you take a slice of the block and you can see the pattern you have made. You need to carefully clean to slice on both sides as the colours will bleed into each other. Then items are made by wrapping slabs around moulds to form the desired shapes.
Careful drying is important as uneven drying can cause cracks, especially along the joints between the coloured porcelains. Porcelain also has a strong tendency to warp and careful handling and drying helps with this. It usually takes around 2 weeks before the pieces are dry enough for their first firing.
The first, or bisque firing, takes the pieces up to about 1000 degrees Celsius. They are thoroughly sanded with wet and dry sandpaper to remove the last of any smudged colours. At this stage the colours are not what you will end up with as they change quite a lot once fully fired. The pieces are then glazed and fired to 1280 degrees Celsius. I only glaze the inside of my vases and lampshades. Once fully fired, the outsides are polished to a soft sheen. My nerikomi earrings and decorations are not glazed but are carefully polished so they feel lovely to the touch.