hundreds of tiny bubbles appeared while kiln-carving -- why?

[RonnyR]

As far as the kiln-carving not being crisp, my experience with 96 Irrid, which I believe is Tin Oxide, is that it does not stretch nearly as well as the non-96 Irrid, which is Titanium Oxide, but does burn off if fired up. I think the bubbles have to do with your rapid ramp to process temp, as your piece slumped around the central KC fiber paper, and trapped air, as the metallic skin broke the air up into tiny bubbles...

[Barbara Muth]

That looks exacltly like the spongeing or pitting that sometimes happens, particularly (but not exclusively)with silver irrid that has been fired shelf down more than once. I have yet to find a way to rescue those pieces. I am so sorry.

[Flo Ulrich]

Sounds like the bubble problem has been id'd. Now, as far as the incomplete slumping over the kilncarving, remember that different colors of glass with have different viscosities. Some glasses are softer and will conform to shape at a lower temp while others need to really feel the heat to move. Of course, there may be other factors in the mix as well (such as thickness). The only way to know this ahead is through testing so that you have an idea of the characteristics of the glasses you're using. Otherwise, plan the firing schedule so that you can be there to watch when it reaches process temp and add time and/or heat to those less cooperative pieces.