White Jade Finish

This is how Jade-Finish is made: by terry hagiwara
(I found some call this "Naked Raku". Don't you think we need more poetic name for this?)

1. Apply terra sig. on the bone-dry surface and burnish.
   • i use ball-clay slip for terra sig.
   • burnish when the terra sig. start losing its wet appearance before it gets dry
   • this means, apply terra sig. and burnish patchwise, if necessary, over a large surface and burnish the entire surface
   • important: the piece must be thoroughly dry. if not, moisture of the clay permeate into burnished terra sig. later and disarray the clay particle alignment (by swelling), thus causing the surface to lose its sheen. retaining surface sheen is crucial to obtain the "wet" (shiny reflective) black surface eventually.

   how to make "colored terra sig.
   

   • terra sig. can be colored for colored surface. this is easily done by adding Underglaze into clay slip.
     
   • some colors, such as red and orange, are not available to my knowledge.
   • metal oxide can be also used. my favorites are:
     • Red Iron Oxide for Pink to Brown to Kaki Red
     • Chromium Oxide for Green
     • Cobalt Oxide for Blue
     • Rutile for Tan
     • Manganese Oxide for Grey
     • Nickel Oxide for Greenish Grey
   • how much to add? try by yourself.
   
   
2. Bisque fire to cone O9 or O10.
   • this is important: if fired to O6 (as in regular bisque-firing), the surface lose its sheen.
   
   
3. Apply/brush thick clay-slip for design on bisqued surface.
   • this slip works as a smoke-resist. do not apply where BLACK surface is expected.
   • slip thickness controls the shade/density of crackles, i.e., the black crackles on the surface after smoking.
   • see below for different slips for different finishes.
   
   
4. Apply low-fire (O6) clear glaze on top of the slip.
   • this is optional, but highly recommended.
   • the glaze, when half-done in the heat, works as a slip-resist retainer.
   • without thip application, the slip smoke-resist is prone to flaking off, leaving undesired black patches, though these patches are also attractive in some cases.
   
   
5. Fire and smoke.
   • if you are using raku kiln, fire to low temperature, just high enough
     • to burn off 6B pencil (or marker) lines, if it is used for design-contouring
     • or for the glaze to start showing a sign of melting, but before it melts.
   • place the piece in a smoking chamber/can.
   • smoking doesn't require red-hot firing as needed for regular raku glazes. just hot enough to ignite paper or saw dust in the smoking chamber (can) to generate smoke.
   • important: take the piece out of fire before the glaze melts. otherwise, the glaze and slip stay sticked to the piece: No smooth Jade Finish, any more!
   
   
6. Remove (glaze coated) slip from the surface.
   • if properly fired and taken out of fire, the slip will fall off easily from the surface.
   • some slip sections may be stubborn. they can be removed with a wooden spatela.
   • do not use hard metals to remove them. it may scrape off the terra sig. underneath, leaving scars on the surface.

different slips create different finishes

• the difference of the clay slip is the major factor to create different shades/crackle patterns of the smooth surface.
• in addition, the slip fluidity, the slip thickness, glaze thickness, and the temperature also affect the finished patterns
• my choice of clay slips are:
  • the same clay used for the pottery piece to create a plain shade
  • china-clay (EPK) slip for faithful retention of brushing patterns.
  • with china-clay alone, the crackles are so finely networked. this property can be used to create black/gray lines/structures as shown.
  • by mixing china-clay slip with "pottery"-clay slip, the crackle mesh size can be controled, while the slip still retaining memory of brush strokes.
  • instead of "pottery"-clay, a mixture of silica and china-clay (like kiln-wash) can be used to bring similar effect.
  • clay slip may be placed strategically to enhance white pattern on black background.