B-Mix vs. Porcelain

Gabriel,
In my humble opinion, porcelain is King. Yes ,it's more expensive. The overall quality of the crystals and how smooth you can actually get the surface of the clay body is superior. I spend time in the greenware stage trimming and smoothing the pot. The advantage is you get exactly the shape you want. With b mix,the sand or grog, whatever they're using seems to always make it rough. My porcelain clay body is very white. Once again my humble opinion, the whiter the surface the less influence it will have on the color of the crystals you're going for.

I've been throwing porcelain for 10 years. After you spend some time with it, you'll never go back.

Have fun
Russell

Thank you, Bonnie and Arnie. There isn't any sand in B-mix or the body I use, they're just generally equal amounts of kaolin, ball clay, feldspar and silica, which according to some is the standard "25-porcelain" mix, though the ball clay prevents translucency and does tend to darken the fired product. Perhaps they are using 200-mesh instead of 320-mesh silica. I have noticed that my body isn't as white as true porcelain, which is typically 50% kaolin to replace the ball clay. But since I'm throwing in the neighborhood of 20" height, it just seemed that the mix I was using is less likely to collapse on me. Perhaps I need to bite the proverbial bullet and spring for a decent porcelain, because I do want that extra brilliance.

Could it be the ball clay that introduces the rough texture? I too smooth my greenware with a polished stone, but that doesn't hold well after the firing, so sometimes I sand the bisque with very find-grit sandpaper.

I think your advice, Arnie, about spraying the surface with a porcelain slip might work for me, but perhaps I will just switch to pure porcelain. That seems to be the consensus so far.

Thanks Greg. I think I'm getting a feel for the balance —— when to use porcelain for a whiter background, and when B-mix is allowable. I did notice in my recent firings, which were with CuCO3 and MnO2, which produces a nice, light aqua green, that up around the rim of the vase, where the glaze flowed rather thin, that it had a heavier cream color hue under it.

Yes, that seems logical, Adam. Is your porcelain your own formulation, or do you purchase it pre-mixed? I bought 20Kg of halloysite kaolin from New Zealand a while back, the same that is used in Southern Ice. I was intending to formulate my own, super-white porcelain, since I live in the northeastern New Mexico desert, 40-miles from the nearest town, and 350-miles from my supplier, but haven't yet gotten to it.

Arnie, do you apply your slip on bisque or green? I haven't done much of it, and usually it is in the form of a stained slip I fire on to bisque at Bill Schran's recommended ^03.

Hi Gabriel,
I use B mix 10, B mix wood, 550 and 570 generally to cone 10 flat and beyond.
Here B mix 10 fires with flaws. B mix wood doesn't but warps drying ( the others don't here).
I prefer 550 and 570 but in my experience they don't throw as well as either B-mix.
The 550 I am finishing now is too soft and "drains" on larger throwing attempts.
Have been experimenting with a 550 slip over B-mix.
Cheers,
Gordon

Gabriel:

An easy way to address this problem is to make a slip out of porcelain body that you like; works well for you. Just cut 2-3lbs off, and slurry it down to a slip viscosity. The COE differences between B-mix and most porcelains are not that great. Any white body stoneware has a fair amount of kaolinitic ball clay, and often times EPK. Run a test on a simple cylinder; see if it works for you.

Tom

Gabriel:

I prefer greenware; I think it bonds better, and it is one less step in the firing process. But like all things ceramics; potters do what works for them.

Tom