Embedding Images Into Engraving

I've started working on some blanks for engraving cameo portraits into, using painted imagery layered into the panel. This one is painted, and some next ones will be laser engraved. I enjoy drawing in this way, laying down a matt of paint and then scratching it off to reveal the image.

This is float glass, painted with enamel. I fired the enamel on first in the small architectural glass kiln to 580 C for 15 minutes, before fusing the two layers of drawing and an extra layer of sheet (to give me a buffer for engraving) together with a sifted payer of optul white powder on the top.

I put dams around the piece to make the heat come more from the top than from the sides, to help prevent bubbles from forming, and fired it on the following program:

1. 150C/hour to 460C hold 0:00

2. 150C/hour to 670C hold 1:30

3. 999C/hour to 820C hold 0:15

4. 999C/hour to 548C hold 3:00

5. 15C/hour to 511C hold 0:00

6. 50C/hour to 60C hold 0:00

For the most part, the bubble squeeze worked, most of the surface was pretty bubble free, but there were a couple of pretty bad ones near some of the bees. I think next time I paint by hand, I will fire to a higher temperature to make sure that the surface of the glass, including the painted images, are totally flat. Also, I hate float glass. It's green, and makes me uncomfortable.