Making Things, part III: Burnishing

Let us begin.

Clay comes in many different textures. The texture of the clay depends upon the concentration of grog, a sand-type particle responsible for strengthening the clay and making it plastic. Porcelain has no grog, which is why it is so fine, and also why it is nearly impossible to throw with. White stoneware, which is what I use, has a middling amount of grog. Burnishing is the process os pushing the grog/sand into the clay body to leave an even, silky texture. Normally glaze would provide the glassy outer surface of a pot, but since these won't be glazed, it must be attained by burnishing. 

While the piece is still turning on the wheel, once it is completely formed, I smooth the outside with a metal rib to kick-start the process. I let it dry overnight until it is what we call leather-hard - not yet like stone, but no longer wet. Then I take the back of a metal spoon (because that's what I have - professional potters suggest smooth tumbled stones, but a spoon works) and burnish the outer surface with small circular motions.

Here's the side of this piece that hasn't yet been burnished, dull and rough. 

Here's the other side. I don't know if the sheen shows up in the picture, but the clay feels like glass. This is after the first burnishing, so all the imperfections are visible. Burnishing must be done in two or three stages; the first one is shown here, and during the second one the piece is almost entirely dry, and a light coat of cooking oil may be applied to add even more gloss. I'm not to that point yet; will update when I am.

Here's a postscript: Today I made five new pieces in addition to the one that's been bisqued and the three from yesterday, less the one which broke, for a total of eight. I haven't set a number goal yet, so I will here: let's aim for thirty well-made, well-trimmed, double-burnished vessels by the time I fire, and if I exceed that, so much the better.

(Source for burnishing information: http://vickihardin.com/articles/pit-fire-ceramics.html - cited in my complete bibliography)