I fire my kiln to 2,400 degrees in a reduction atmosphere, depriving the flame of oxygen so that it rearranges the molecules in the glazes. A copper penny left out in the rain turns bright green when it rusts – oxidizes. When I heat it in the absence of oxygen, it turns bright red:

Likewise, a little iron makes a reduction glaze turn a Celadon blue:
A lot of iron yields a black Temokku:
put them together and things get interesting:
The Temokku glaze also works well with a red/pink glaze called Peach Blossom that I got from my first teacher, Tom White of Northfield, MA.

I like a real heavy reduction, so that the unburnt carbon in the kiln gets trapped in my Shino glazes. Shino is the Japanese word for “white,” but my traditional shino takes a ride down the gray scale when I choke off the air to the burners:
In the heavy reduction zone at the top of the kiln it can turn almost black:
I also use an “American Shino,” developed by the potter Malcolm Davis. It contains Cedar Heights Redart clay to impart an orange color, and lots of soda ash for fantastic reduction effects:
If a shino pot is next to a copper glaze in the kiln, it can get a “blush” like this:
And the orange shino brings out the best in the white, as on the outside of this bowl:

I’m always working on new glazes and new combinations, and lately I’ve been experimenting with colored clay slips underneath my celadon and Shino glazes. Every kiln load brings surprises that can lead to something new.