Saturday, April 28, 2012

'Minford Silt' glaze?

We're preparing to fire the wood-fired kiln tomorrow, and I've decided to glaze quite a few pots this time using this wonderful material an unknown customer brought me from Ohio a few years back. He called it a blue clay.

It's great stuff. I actually threw a pot with it and bisque-fired it to about 1800 degrees F. It had a nice ring to it. But when I fired a small piece to 2,200, it melted. So, I started using it as a glaze. Fired to cone 10 and above, it produces a nice brown glaze and reacts well with natural ash.

I can brush it on a wet pot right after throwing, and I can dip a bisque-fired pot into it, no problems. I wish I could find some more. I've only got half a 5 gallon bucket left.

I searched online and found an old post on Clayart by Steve Blankenbeker a ceramics engineer working at Cedar Heights Clay Company who was posting about research into finding a clay like Albany Slip which used to be a popular glaze among old-time potters until they stopped mining it. He states that there is a glacial deposit of clay in southeastern Ohio called "Minford Silt" that is similar to Albany Slip, but requires a lot of flux to get it to melt.

My customer must have found the deposit he was hoping to find. I wish I could locate that customer.

Apparently, this material I'm using is an alluvial clay, a sediment that has been deposited by water from rivers or streams.

I just know it feels good on my hand when I mix it. It's so soft and slippery. And it seems to love the atmosphere inside my wood kiln.

Ohio Clay slip

Here's it's sprayed on a bisque-fired tree platter

Ohio clay reduction cooled

Ohio clay - heavy reduction

Ohio clay cooled quickly

Friday, April 13, 2012

Fuming in Electric Kiln Creates 'Directional Pots'

Most of my focus this past year has been on wood firing, but I continue to fire pots in my electric kiln. Pots in the wood kiln tend to have two sides to them. The side toward the flame and the side away from the flame - directional pots sort of. Ash tends to fall on the side toward the flame, and this ash will melt and form its own glaze, or it will melt into an existing glaze on the pot and change its look.

I unloaded my electric kiln yesterday and had a couple of pots that had this "directional" look. Kind of cool. What happens sometimes in an electric kiln is some glazes will fume a lot and the fuming will affect pots located right next to them. I've seen this a lot with a turquoise glaze I use.

But the pots that were affected yesterday were ones set beside a glaze that I mistakenly put manganese instead of cobalt. Apparently, manganese has a tendency to fume, at least in this particular glaze (50 percent gerstley borate/50 percent plastic vitrox clay).

Here's the two pots:

This is the side away from the fuming

And this is the side toward the fuming

Here's the placement in the kiln

Here's a wood-fired pot, flame side
And back side (away from flame)

Sunday, April 1, 2012

Taking a Break - sort of

Someone once told me Sundays should be a day off, but that doesn't seem to work here. I'm working on 40 more foot-soaking bowls for an order. These bowls take a bit of time to make as they are two pieces. I make the bottoms one day, the tops the next day, trim the bottoms the next day and put them together the next day. Sometimes, I can trim bottoms the same day I make tops.

So, I sort of took part of the day off today by making some pots for myself to fire in the wood-fired kiln - some two-piece pots, as I'm currently in two-piece mode. Then I spent the afternoon trimming and covering bottoms for the foot-soaking bowls.

Two two-piece bottles and vases amid the mess

Parts covered and ready to be put together tomorrow
And here's a condensed video of me making the bottom to a foot-soaking bowl using 16 pounds of clay: