Thursday, July 16, 2009

Porcelain, the Diva of Clays . . .

Or When White Isn't White

I have been commissioned to do a large vessel for holding wash cloths and perhaps even small hand towels by my good friend and vocal instructor, Scarlett Hepworth ( She was hoping I could do this in porcelain or if not, then in the black stoneware which I like to use. I mentioned porcelain can be very finicky and often doesn’t lend itself to larger pieces. According to the clay and glaze guru, the late Daniel Rhodes, the more pure the porcelain (using mostly kaolins, the white burning clays), the more difficult it is to make anything out of it.

I love working in porcelain. But I can tell you from my own personal experience, working in porcelain is a lot like trying to form pieces out of butter. It’s because there is little if any grog in porcelain. Grog is clay which has been fired, then ground into various degrees of fineness and added to clay to make it more forgiving when forming large, thick walled vessels or sculptures. Even if you are able to create a magnificent bowl or vessel in porcelain and get it from table or wheel to kiln in one piece, there is no guarantee it will make it out of either the bisque or glaze fire in tact. Porcelain is truly the diva of clays.

I have been using a couple of mid high fire porcelains for the past year or so and only recently did I realize while they both fire at the same temp. (∆5 – 1180 degrees Centigrade) they are NOT the same shade of white. How is that possible? Well, it has to do with which of the many different kaolin clays are used. It became all too apparent to me that I was mixing my porcelains when I threw a small vessel for a commission and began to carve it while it was leather hard. All of a sudden the outer wall looked like a white snow leopard –very soft white white spots all imbedded in a slightly more grey white. I know you can go to any paint store and find 10 different shades of whites with all kinds of designery names like Sea Pearl, Soft Shoulders, Swiss Coffee (yes, white!) or for those who might not be really sure of using white, Timid White, but I was a little taken aback when I finally noticed the discrepancy in the 2 porcelains’ whites. Would I have to redo this piece, which was almost finished and ready for the bisque fire or would I be lucky enough that when fired this wouldn’t be noticeable? Now that the piece is dry and ready for the bisque, I can’t see the spots so I’m hoping this won’t be an issue.

On Monday I was looking through my half used and reconstituted bags of porcelain hoping I would find enough to make the large thrown bowl portion of Scarlett’s piece. I did find about 6 lbs of the grey white, a bit hard but still wedgeable and enough of the soft white which I’ll use for the hand built part. I threw the bowl yesterday – I left it on the wheel 11 ¼ ” w x 7” h. Today, now that it is slightly dry, I was able to nudge it about ½” wider, making the bowl shape more graceful and now a bit over 5” h. Yes, you have to take your time with porcelain – patience is ever the virtue with this clay. And really, when isn’t it when you work in the mud?

1 comment:

Leah Virsik said...

Bobbie! Congratulations on getting your blog up. It's great. I enjoy hearing about your process… the details of the whites… and about learning what grog is. I love how you really got some content up before sending it out. It's been a real treat to meet you through Alyson B. Stanfield's Art Marketing Salon I'm enjoying watching you grow and move forward and make your mark in the art world! xo Leah