Castable core recipe + ratios

At long last I have tracked down fire clay.

Any feed back appreciated on this recipe and ratio scheme to cast a core and then heat riser.

For simplicity sake I am looking at a volume ratio of vermiculite to "the other stuff" (which will be gently nudged and beholden to the mixing process and that consistency of "dryish-pop apart" clumps versus mooshy)

My "other stuff" is simply going to be, in a 1:1 ratio, fire clay to firestop50.

My goal is to make a bombproof core at a moderate price. I don't have access to local clay and I was hoping to not spring for premade castable refractroy products, thus I feel I am working the middle here, and hope to add something to the community.

This is all the brain child of Matt W's cast core video, and when he said "I throw a handful of furnace cement in to toughen it up", I immediately thought, what about way tougher?!

Thanks so much for posting any thoughts, ideas, questions or comments.

This craft is blossoming because we are making it so! It's good for us (to be cozy) its good for the trees (maximizing their potential and minimizing our consumption) and good for the environment (by minimizing emissions). WHAT'S NOT TO LOVE.!

Good day gang~p

Prescott H. Paine : ''Fireclay'', is called fire clay for very specific reasons, all clays expand when wet and contract as they dry/cool, the greatest difference between expansion and
contraction is between wet clay and dry clay, Fireclay gets its name from the fact that it shrinks the least, Sand is put into the mix to keep the clay at the micro particle level
from shrinking enough to crack, So it is fire clay because of all of the clays in the world this stuff shrinks lest, It has nothing to do with how much heat it will take !!The only way
clay can be made to crack less is the way Potters have done this since before recorded history, If you are interested,you can look up Grog !

Go to the ''A castable core'' and reread it again, your ratios need fine tuning, you need to make test bricks of your ratios and test them for strength, more is not always better !
For the craft Big AL