I had to physically push down on the center of the plastic to get it stretched.

When the plastic cooled I removed the wooden frame and pulled it out. It looked great! Maybe not as convex as I needed, but definitely a good step towards my ultimate goal.

Next it was time to move up to full size 15" domes.

I cut a larger jig, sandwiched a new sheet of plastic and squeezed it into the oven.

Actually, I first tried a heat gun, but I couldn't heat the sheet fast enough to get it to soften up. The oven was the obvious next step.

I laid out a sheet of aluminum foil in case my plastic melted all over the place. I cranked up the oven to 550F and turned on the broiler (in this case an overhead electric heat coil).

Nothing happened.

Well, actually, nothing happened until I looked away for a moment. The plastic drooped down to the rack!

I threw open the door and pulled out my project. Bubbles!

Damn. I missed the "hot enough to be pliable, cool enough to not bubble" heating window. I was going to have to be more vigilant.

On the second attempt, I turned down the heat and stuck with the lower heating coil only, not broil.

I set the heat at 400F, kept the door cracked open and a close eye on it.

As soon as it started to droop, I yanked it out. I wanted a slightly more concave dome, so I gently pressed down with oven mitts. I know this sounds crazy, because I wanted a perfect smooth curve, but the hot plastic was elastic, bouncing back to smooth.

Cool and out of the jig, it looked awesome! A perfectly smooth bubble.

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