Cup: Marbled Soda Dusk

This is one of my absolute favorites, just a perfect soda moment on a cup marbled with clays stained with soda slips. 

These marbled vessels are such a delight to make and such a long process to get there.  I stain the porcelain several different colors with mason stains and soda slips then lightly wedge them together in cup-sized amounts and leave them for a week so the clays can acclimate to the same moisture level .  Then I throw them on the wheel and then trim or scrape the entire piece to reveal the swirling, unpredictable patterns.

Each soda fired piece is one-of-a-kind as atmospheric firings are unpredictable and can yield stunning results.  Soda firing takes an enormous amount of time, energy, labor and resources and is usually a community effort.  In the soda firing process, soda ash (sodium carbonate) is added to the kiln at cone 9 (2300°) and the sodium vapor combines with silica in clay to form a sodium-silicate glaze.  The soda also interacts with the slips and glazes to create swirling unpredictable colors that shift and change around the piece.  The marks on the bottom are from the wadding used to hold the piece up off the kiln shelf so that glaze drips won’t fuse it to the shelf.  They can leave lovely flame marks and are a telltale sign a piece is soda fired, though they don’t always happen, especially in low soda areas of the kiln.