burnishing?

Here's the method I use.

Oil the piece with organic oil and rub in a curcullar motion with a smooth object. I have never done this while the piece is rotating, only while I hold it myself. The process takes time and patience. Do not press hard. Use a steady, even pressure. If you press too hard, you leave little whorls on the piece. Do not over-burnish. The burnished area will start to powder and flake off if you do.

The river rocks used for this process must be very smooth, ie tumbled through the river bed for a long time. They are hard to find. You can use rocks smoothed with a rock tumbler. Any lapidary shop usually has some for sale. Or, the easiest, a good quality stainless steel spoon back works great. Just be sure it is hard enough that it doesn't leave metal on the piece.

Take frequent rests, especially if you've never done this before. A dear friend of mine who's work had just been accepted by a major gallery developed carpel tunnel syndrome and had to quit making his beautiful burnished pots. I am fortunate to have one his first pots that I bought at a local art fair.

Fire no higher than cone 04. I have seen pit-fired, dung-fired, and sawdust-fired burnished pieces. Higher temp will destroy the burnish. Finished pieces are pourous and not considered food safe. However, they are beautiful decorative pieces. Vases make wonderful containers for dried folliage and flower arrangements.

Jan C.

Native peoples in the southwestern US used to use (maybe still do?) a thin coat of oil (olive or vegetable, not motor oil) when burnishing. That might work better for you. (It burns off in the bisque.) Personally, I've always used a tablespoon, not a river rock. (Easier to grasp with these old arthritic hands.) I know some people that burnish with pieces of glass, plastic grocery bags (that works, try it!)...your choices are endless. You should be burnishing when the clay is leather hard, not bone dry (though with the oil on it, you might be able to.) The whole idea is to compress the clay surface and create a smooth surface with a shine. Careful though, as this will affect fit of glazes sometimes, and could lead to crazing or other glaze defects. If your clay is heavily grogged, you should be burnishing leather hard, to push the grog bits back into the clay body, and make the surface smooooooth. Good Luck! Wayne Seidl

Thanks for that info. Incidentally I was reading about the pots made by ancient Greeks, who didn't have/want glaze and therefore burnished. I'm not sure what cone they fired at--the source I was reading had been trying to recreate their technique and was using silver's melting point as a guide (melts at 962 C or 1764 F, I think this is cone 07). Anyway, it was mentioned that the porousness of their wares was a good thing in the Mediterranean climate, because the water that seeped through the pot walls evaporated and kept the pot cool, thus the pots were said to "sweat". Probably this was not desirable for hot food but for water and wine it was ideal.

Thanks. About the smooth shine, I heard that because silica particles are essentially flat chips, burnishing has the effect (as does throwing) of lining them up flat against each other, increasing the bond between them and forming more of a continuous glasslike silica surface. Grog would mess that up a bit though, perhaps I should use porcelain for burnished pieces.

I've burnished with both a very heavily grogged (like concrete!) raku body and with porcelain, and gotten the same result. I chose to burnsih leather hard, and without the oil. Best of Luck! Wayne

A good technique with a heavily grogged clay is to make a sieved slip out of the same clay and slip the piece with it before burnishing. This is a particularly good method for pit firing and other types of raw firing where thermal shock resistance and the desire for a smooth surface collide.

Steve Bath UK

In article , Wumpus writes

i try my own "low budget indian pottery" and often burnish right on the wheel after trimming (i throw indian pots, that's why i call them "low budget"). i use the metal rib or a spoon. sometimes i use a pensile so the graphite lead also can add itself to the pot surface.

i use a stoneware clay and on the "nicer" pots i'll coat the leather surface with porcelain slip, cone 6 (because it's handy).

i bisque fire the pots and coat them with a graphite & salad oil mix. then i put them into cans with sawdust and fire the cans until they turn red. "can red". i don't know what cone that is...

i get a pretty good black finish, with the burnished look. one day i'll get better at tieing feathers to them...

see ya

steve

steve graber

I use polished river stones I bought from craft stores or Wal-mart. They work very well. The more polished, the better.