Carving porcelin

[myxpykalix]

my search resulted in no hits, so let me ask....

Is porcelin too brittle to carve designs into? Do i need specail bits or can i use my trusty centurion bits? Will i hurt them trying to cut porcelin? Any special hints on depths, speeds I need to be aware of?

[landdesign]

Jack,

I believe for the most part Porcelain is way to hard and definitely too abrasive to "carve" with traditional bits. Grinding might be a better definition of what you'd need to do. you would also have to remember that the dust from all this would be nasty on the bearings of your spindle and your lungs might not like it too much ether.

Erik

[myxpykalix]

Do you think there is that much difference between porcelin and marble? My understanding was that marble was ok to cut with conventional bits.

[landdesign]

jack, porcelain is a 7 on the Mohs scale of hardness and marble is a 3. the scale is logarithmic and goes up rather quickly.

Erik

[gerryv]

Jack, I seem to recall that there are several types of porcelain that vary in hardness but they are generally much harder than marbe and even granite. I think the result would be a cherry red, rounded tool bit tip and fracture lines or chips in the material due to its poor heat transmission. Diamond bits or grinding is the norm I believe. Then again, that's info from the dusty old crevices way back in my head so please don't take it as gospel.

[jamesgilliam]

Jack, Since my wife and I have been taking pottery lessons I will chime in here. Porcelain is a type of clay. There are different types, all having their own distinct properties, and hardnesses. Depending on the type and makeup some are fired to a cone 5 while others are fired to cone 10 to maximise their hardness and vitrify the clay. For the most part any decorative carving done, and this is with any clay, in the greenware stage, before it is fired the first time. At this stage it is very fragile. Once it is bisque fired it is more stable, you can sand the rough spots and it is possible to add a few more details, but it is still easy to break. Trust me I have done it. Glaze is then applied, and it gets its final firing to melt and bond the glaze to the piece, this is where it reaches its maximum hardness.

Erik is on the right track with grinding being the best way to do it. And do protect your lungs, there are things in some glazes that are pretty nasty to your health.

[applik]

Why don't you just carve your own mold. Pour the porcelain in. Clean, then have it fired. Voila, 3D porcelain. Just a thought.
Bluebonnet

[erik_f]

Slip casting is what Shari is talking about...and that would be the way to do it. Also you will have to scale the size of the mold depending on what type of clay you use and how it is fired. Usually shrinkage is around 10%.

[jamesgilliam]

Shari and Erik are right, slip cast would be the best. Shrinkage of 10% to 13% is the norm. Things to consider: Type of glaze, some will not show their true color in reduction firing. What cone does the studio fire to? This one is probably the most important. If you use a cone 5 clay or glaze you can't fire to cone 10. All you will do is have big mess in the bottom of the kiln.

[myxpykalix]

Thanks for the information as that is very enlightening. However my initial and only interest in wanting to carve the porcelin was an idea i came up with after reading "The Economy" post and walking thru my local Habitat for Humanity store.

People have been making suggestions on how to augment their income and there was a pile of free porcelin tiles sitting outside so i grabbed a couple and thought one way you might be able to make some money plus give back something was to take some porcelin or marble tiles from there and carve some nice designs then donate them back with the understanding that a sticker with your name and phone number be left on them.
People might come in to buy them, there won't be enough made to finish a project so the customer might call you to carve more for them.

You could possibly make up a small set of samples for display there with a portion of the profits to go to the store. I'm doing that for the local store here.
Based on what i've learned from you about porcelin, that is not the way to go but maybe marble is.