I finally put the edges on my polymer clay focal bead from a few weeks ago. Unfortunately when it came out from the final bake it had cracked 😦
I did notice a tiny crack after baking the back onto the dome which I thought was due to the air expanding inside the newly sealed dome. Therefore I drilled a vent hole via the threading holes. When I make pieces like this, which I bake several times, I usually to a partial bake for 10 minutes or so, and then a full bake at the end. I suspect the cracks are due to the partially baked clay waiting around for a few days before the full cure.
So from now on I’ll be doing longer cures between and hopefully avoid the cracks.