Carbon Painting
We call our technique "carbon painting" because we think of painting and manipulating the carbon (either directly or the smoke) in a painterly fashion. Rather than simply laying horsehair against a hot pot or a feather in place of horsehair, we use a pallet of techniques to create some pretty outstanding results.
It would appear that that not all materials absorb smoke and carbon at the same rate or in the same amounts (if at all). We use that knowledge to our advantage. It is rather like sealing parts of a deck with weather sealant and then strategically throwing water on it to create patterns on the deck. Of course we can't use weather proofing as it would burn away, but you can sort of imagine what sealing some of the pot might do with smoke. To accomplish this we use a number of slips and underglazes that have water soluble chemicals in them and let them more-or-less "bleed" out into the surrounding clay.
One primary principle that we use is: smoke rises. Duh. But that means that how the pot is held or set will determine where the smoke will (or can) be absorbed. By rotating the piece while placing the carbon, one can get smoke to drift across the surface is some pretty crazy ways.
Now remember, all this twisting and turning has to be done quickly as once the piece drops below about 900 degree Fahrenheit the carbon will have less effect on the piece. If one starts the process too soon and the pot is too hot, the carbon will seem to burn into the piece nicely and then burn away leaving a faint hint of patterning. A great deal of variation can take place with practice and being "one with the clay" or more precisely, "one with the temperature."
We like to use a variety of feathers, but find ourselves using goose feathers most of the time. The beautiful patterns on feathers has nothing to leave behind on the piece as carbon traces. It is the shape of the feather and the volume of the carbon that makes the feather useful. Feathers which are too "flimsy" are not very useful (as in chicken feathers). We purchase and trade for feathers (particularly peacock and emu). We use the secondary feather with more down, shying away from pin and wing feathers.
Sugar is also a great source of carbon, but as with all of the carbon painting resources, too much can be well...too much. If not careful one can end up with a wad of black.
Our horsehair comes to us from our favorite luthier. He rehairs fiddle bows (not violins...we call them fiddles because of love of olde timey and Irish music). I acquire 190 proof "Everclear" while we spend time at our cabin in Montana and trade the booze to for him for the horsehair which is removed from worn out fiddle bows. He uses the Everclear to make varnish for repairing musical instruments. He and I play Irish music together. We are not sure how much the rosin from the spent bows plays on the pots, but I'm not changing my source of horsehair anytime soon. Just ot make it uber clear, many of the bows that he rehairs are from the 1800s...seriously old and seriously cool.
Why not hair from humans? All the human hair I've tried has been too thin. There was not enough carbon in the bulk to leave behind. Various types of hair may result in more carbon. The hair I tried didn't work well enough.
Alternate animal hair and fur does typically lend itself to results other than black blobs. Fur from dogs and cats, while a romantic notion, don't work particularly well. The fur from pets could be "dubbed" with a linen thread and applied to the pot. Wool from sheep and alpaca have been tried and the best results came from single ply yarn in a "lace weight"...fine stuff. The bulky and worsted resulted in massive black blobs.
This is one of the technique groups where the weather can play a significant role. Well, wind plays a role. Remember that the smoke will rise...it will also blow away. So if one wants to play with the smoke, still day can be the goal. But if one is more about the carbon trailing left by feathers and hair a tad of wind can work well. Wind in any amount will cool the pot more quickly and may dictate the speed that one needs to work.
Questions? You can always email Jim and ask him for some additional clarification.