Well, have you looked into improving your clay body strength or adding materials that make it more raku-friendly? I know you have probably thought a lot about this already, but a friendlier clay body could open new vistas.
I have... in that I've tried a range of pre-made clay bodies. What I haven't done is tried a re-formulated clay body. For example, Cass (in another thread) recommended adding 3-5% kyanite. I may ask my local supplier to try this. Other suggestions would be welcome.
Have you tried Piepenburg Raku clay? It contains kyanite but I imagine most raku claybodies would..Maybe Cass meant an additional amount of kyanite above what is already in it? It has been years since I have done raku but you mentioned in another thread that you think the cracking occurs either in the kiln or in the reduction chamber. Would it be possible to fire the glazes to maturity then let the piece cool in the kiln to about 900 or thereabouts, then remove it when it is still hot enough to ignite the combustibles but not at top temp? Maybe avoiding the quartz inversion temp at about 1000F would help, just a thought.
Thanks for the thoughts Min.
I've used Pipenburg- and I definitely see a reduced fracture rate. The problem is that pipenburg (like a number of the specifically formulated 'Raku' clays) is full of grog. For the surface carving that I do, the grog yields a ragged line, or grabs the carving tool and throws it off-course.
The second idea is interesting... but a number of the most interested surface effects seem to take place at higher temperatures than 900 degrees, and I'd hate to lose the organic character of the surface.
I've thought about firing in a sagger and then adding combustibles in-situ (eliminating the rapid cooling that happens when you move your wares from kiln to can. Not entirely sure how to do this safely though.
I'll be trying kyanite as an additive this weekend.