Saturday, February 6, 2016
when things go terribly, horribly wrong
You might remember I posted about carving the rose leaflet out of wax for a platform for the small pink flower to sit on.
Well, I finished it and Marc made the mold and I filled it and it went straightaway into the kiln late afternoon on Wednesday. Marc set the schedule for drying the mold overnight and then moving on up to casting temperature on Thursday. So he went over to the shop Thursday morning to check on it and the kiln had malfunctioned and it was glowing red hot at nearly 2300˚, hot enough to melt batch for glassblowing. Casting temperature for our work is generally around 1500˚, sometimes hotter depending on how deep and narrow some of the elements of the piece are.
He shut the kiln off and cracked the door and by afternoon, while it was still too hot to take the mold out of the kiln, it wasn't too hot to take a picture or two.
So here's what a closed mold looks like when you get it hot enough to boil the glass and mold material and fuse the plaster and silica flour to the glass. (For you glass people out there I used Bullseye transparent lt. green, olive, and grass green in equal parts, all fine frit.)
The kiln shelf is toast, ruined as the glass and plaster at the bottom fused to the ceramic shelf.
It blasted two holes through the mold at the point of the leaf tips and the mold, which is usually soft as chalk after firing, was pretty damn hard and I needed a hammer and a putty knife to chisel and break it off.
I got as much of the mold off as I could and then soaked the piece in vinegar for an hour or so and then used a metal brush to get as much of the mold material off that was going to come off. What remains is hard even though it looks friable.
So instead of a nice rose leaflet, I have an alien geode.