Getting into this experimental process pioneered by Rick Berman may end up a little complicated, so please ask for clarification if you need any. I'll try to keep things simple.
Two popular types of ceramic firing are raku and salt. Raku firing comes from Japanese tradition, but it has an enormous American following, and American raku has its own unique look. Salt firing has been around since potters realized using driftwood to fire their kilns could produce interesting, glossy glazes. The salt at high temperatures eats away at the clay and glaze, causing an "orange peel" look on a raw clay body (as well as on the sides of the kiln, making salt kilns very easy to pick out and making them exclusively for salt use).
Rather than try to explain this process, I'll leave it to its inventor, Rick Berman (note the saggar reference, and refer to my last post if you don't understand it). "At any rate, I built a small soft brick (scrap) updraft Salku kiln and corbled in the top with a 5-inch flue. The kiln measured 2-1/2 bricks across and about 15 courses high, roughly six or seven cubic feet. The whole kiln became a saggar, so we eliminated the potato chip cans. Now I'm tumble stacking tenmoku and ash-glazed pots with a half bag of charcoal all through the pots and I'm firing to approximately cone 10 in four or five hours. I use about 5 lbs. of salt and the pots are getting some beautiful black orange peel from the melting charcoal, and sometimes stick together so when they are pulled apart, some dramatic scarification is happening. Remember those nasty Japanese pots mentioned above? Well, with a lot of help from nature, I'm seeing surfaces now that I never thought were possible. Making pots is even more of a joy when you love the surface possibilities so much that you literally can't wait to see the next group of pots come out of the kiln. I am very grateful."