Refractory type used in Thermo-Lite kiln?

[Pluton]

It would be much  appreciated if any of the kiln experts in this forum could help identify the type of refractory brick used in this  1972 vintage Thermo-Lite cone 10 rated updraught gas kiln, as seen in the advertisement below in Ceramics Monhly, Jan 1971 issue.

The refractory is in the form of standard 9 x 4.5 x 2.5 inch bricks mortared together and is therefore presumably not a castable material.  It is cream colored, very soft, much more so than today's IFB, and does not contain sand.  When rubbed it powders, much like a soft blackboard chalk or soft plaster, and it appears to have been both foamed and filled with some organic material that has been burnt out leaving elongated voids with striations on their surface (not obvious in the image below, but clearly seen with a hand lens).

The kiln was purchased used and appears never to have been fired (the dark lower right corner is shadow, not soot).  It has four rather nice burners jetted for natural gas and is similar in concept to today's Olympic brand Torchbearer kilns (and in case you were wondering, it did not come with the penny of same vintage).  

Reasons for asking are twofold:

- The refractory is somewhat friable and comes from a time when asbestos was commonly used.  Although it does not appear to contain fiber (unlike say asbestos cement), I guess that is always a possibility and will handle it accordingly, but would appreciate knowing if that was common practice back then.

- Curiosity; is this simply fireclay whipped up with some organic burnout material?  Why would this gas kiln use a different type of refractory than is used in electric kilns of the same vintage (and current manufacture)?

 

[neilestrick]

Hard to say. It's probably just some version of IFB, but you'd have to test it to be sure. They could have put anything in there.