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Well I have an interesting failure that made me laugh, but I am interested in the possible source of the problem to avoid future such disasters. My results are in the picture above. The round amber colored base split then slid and draped over a corner of the kaiser lee board on which I was firing the piece. Any words of advice would be helpful.

This is the first time I used a stainless steel form and the first time I used fiber paper in a project, so perhaps the misapplication of these components contributed to my problem. 

The project was to tack fuse a "pocket" on to a round base. The round base was previously created using an 11" casting mold filled with fused glass chunks from other projects. The pocket was originally created using half circles of clear glass fused then slumped into a bowl mold. All glass was coe 90. 

The original intent was to glue the clear pocket to the round base, but I was not successful in that regard. So, I decided to tack fuse the pieces together, but did not want to lose the "pocket" in the clear glass. So I decided to put a stainless form between the two glass components, and used fiber paper to separate the glass from the stainless form in case my priming of the form was inadequate. The stainless form was made by cutting a traditional draping cup mold in half vertically. 

I guess I am wondering what most likely caused the base to split and how the split piece could move so far on the kaiser lee board. As a side note, I have not yet been able to extricate the stainless form from the piece, but have not tried much force. 

I have a top firing JenKen fiber kiln, and used the following schedule in the project:
200/hr to 1000, 
500/hr to 1280 hold for 20min, 
fast to 950 hold 1 hr, 
100/hr to 700
What a lot of fun!

as a guess: heatup was way too quickly.

the temp under the middle part was a lot less (because of insulation of the fiber paper, the air under the steel, etc) than the temp of the glass on the sides. it cracked in the middle, slid or blew apart, and then the rest of the heatup to slumping temps formed the rest of the picture.

if the edges of the split a rounded, this is the most likely reason.

to solve it, i'd probably do a

50 1250 15

heatup to form this.

You will also need to put more fiber around the metal insert so that the glass does not grab it on cool down.

Thank you both for the experienced words of wisdom. I never thought of components heating up at different rates, but clearly this is something I need to take into account in future.

What I do not realy understand is what increasing the amount of fiber paper release material accomplishes. I understand that project components may contract differently when cooling, but why would doubling up on the paper make a difference?

As mentioned in my original posting, this is the first time I've used fiber paper and so am not familiar with its usage, other than the care needed to handle clean up.

Thanks again for your thoughts on this subject.

the fiber paper cushions the metal insert from the glass. it is soft and allows wiggle room for removing the form. yes stainless contracts more than glass on cool down but in reality it helps to have that cushion there. R.

Wiggle room totally makes sense.

ThanQ!