We have been working on this formula for years and it exceeds our expectations for what a flame-ware clay is able to do when the pieces are made correctly.

This clay Fires to cone 10, shrinkage approx 11%

A Guide to Flameware

• Pieces should be left thicker than you would with other clay bodies to help with thermal shock and better heat retention 3/8 of an inch or thicker. 
• Pieces should not be trimmed with “foot rings”, but left smooth on the bottom.
• Pieces should be made as even as possible in terms of thickness. 
• No hard edges! Pieces should be thrown and then trimmed to slightly round off all edges.
• Pieces can be hand built, but care should be taken to avoid unevenness and any “weak points”. 
• Many “common” glazes will not work with flameware clays, due to the glazes inability to handle open flames without causing defects. Therefore we recommend our two Flameware glaze bases.
• Research and testing should be used when using any glaze on flameware clay. Any glaze which shivers or crazes heavily should not be used. Both will weaken the clay body and cause possible breakage. Please test your glaze on a flameware test tile before making and using flameware clay items.
• An unglazed, burnished surface also works very well.
• Flameware clay slip, slop, and trimmings should not be mixed with other clay bodies and recycled into “mixed clays”, due to the introduction of low expansion or clay altering materials which may affect glaze compatibility.
• An open flame will expose defects and weak points - take your time and make simple, slightly thicker, more even pieces.
• This clay can become "soft" when hitting cone 10.  Always support extended appendages, handles, spouts, etc so they don't slump, If atmospheric firing- a heavy alumina wax or sand should be used in place of wads.
• Take extra care when firing heavy lids on flameware pots at Cone 10. They may fuse or slump due to the weight if the clay becomes "soft" at Cone 10.
• Clay Planet will not be held responsible for damage caused by poorly made pieces. Poorly made pieces should not be used on open flame.  These pieces may crack, chip or even explode. 
• Never leave Flameware submerged in water for a long time. If not fired to a full cone 10 it is possible for nearly all clays to absorb water over time. This makes them more prone to cracking or breaking when exposed to heat or flame. Always fire flameware clay to FULL MATURITY. A full cone 10 in the case of Diablo Flameware.
• At cone 10 all pieces should have the bottoms coated in an Alumina wax to prevent sticking to kiln shelves.

https://www.youtube.com/watch?v=AQ3Co68gxvI      <- full workshop of the do's and don'ts of flameware