[TheForge] Another hollow sphere idea

[Bruce Freeman]

I just caught up with the postings.

I liked the idea of slip-casting hollow spheres, but agree it would be very slow.

How about a modification to my wooden bead idea:

String wooden beads or styrofoam spheres (~1/2" dia) on a 1/4" dowel.  Dip the dowel in a castable refractory and let it set.  (Repeat if necessary, but preferably have a mix of the appropriate viscosity to do it in one dip.)  Fire "slow" to dry the refractory, then to full heat to fuse it.  By this time the dowel will have burned off, so work over an appropriate material so the whole mess doesn't fuse together.  This should work fairly quickly, once the bugs are worked out.

And to clarify WHY hollow spheres may be desirable:
1) Spheres won't pack tightly - hence burning gases will pass through easily, AND it should be easy to insert the object to be heated.
2) Spheres are relatively strong, so won't easily crush.
3) Being hollow and perforated, the hot gases will (to some extent) pass through them.
4) Being relatively (?) thin shells, there is no issue of heat "from the center" taking long to get to the surface.

The presumption here is that we want the burning gases to do the heating, and not to be heating using heat stored in the chips.

Bruce 
NJ