To continue... Up to this point, I was doing all right. The plaster/silica investment core turned out well. The vermiculite box looked fine. After several iterations, the cut-glass strips fit snugly between the core and walls. But from this point on, everything that could have gone wrong did go wrong. It seems I gambled on too many assumptions and I lost! Any one of those misjudgements would have led to an epic failure.
My first mistake was to assume that priming the vermiculite would keep the glass from sticking. Wrong! I should have used fiber paper lining between the vermiculite and the glass strips, or used primed fiber board instead. My second mistake was switching from one glass to another half way through. Opaque white is denser than transparent tint. They softened at different rates, causing cracks. My third mistake was assuming that strips of thin 2mm glass could be substituted for standard 3mm glass strips. More strips meant more air in between. The total volume of glass was less than adequate causing the sides of the box to slump below the top.
This was by far the most expensive and time consuming project I've undertaken to date. It took weeks to plan, weeks to construct, and 70 hours to fire and cool in the kiln. Crazy! The mess you see is the vermiculite box that I tried to chop away from the (already cracked) glass. The real question is do I understand enough at this point to try it again, this time with a greater probability of success. I haven't decided yet.