This is a technique brought to us by Mark S. Richardson. The basic process has been around for quite a while, and has been known by different names, one of which is “naked raku” (but don’t go getting your hopes up-it’s not that kind of story). As with any firing process, you should wear protective clothing, and exercise all fire-safety precautions. Richardson devised a system for getting peel-away slip onto his pots, keeping the slip intact through the firing and reduction process, and then removing it easily at the end. – Sherman Hall, Ceramic Arts Daily.
Begin by dipping a bisque-fired vessel in the slip. This slip should be mixed to the consistency of pudding.
Immediately place a piece of fiberglass screening (available at hardware stores) around the piece, so the screen is embedded in the slip. This will make it easier to remove after firing, but won’t prevent the slip from cracking to allow for smoke to get tot he ware. Follow the screen with a piece of newspaper. This will will protect it during the firing and keep it from becoming attached to other pieces.
Stack all your pieces in a basket constructed of steel fencing bound together with #10 binding wire (both available from a hardware store) and place in an outdoor kiln. Fire slowly to 1100°F (or until you see color in the kiln).
Using heat-resistant gloves and full heat-resistant body protection, transfer the basket to a steel garbage can with a small amount of combustible material in the bottom and along the sides. It will ignite immediately, so don’t lean over it. Add more combustible material on top of the basket and put the can lid in place so the material smolders and creates smoke (now you see why we’re outside for this).
After the combustible material has burned and the ware has cooled, the slip can be removed by pulling on the fiberglass mesh that still surrounds the pieces. Because the slip shrinks and cracks, but stays attached to the pieces, the smoke can only get to the surface through the cracks. This type of ware is usually still porous after firing, and should not be used for food-surface contact. Refiring will remove any smoke marking.