big bubble dilemma
Posted: Wed Feb 25, 2004 10:30 am
It looks like a volcanic explosion caught in action! The secrets of the ancients rising up to meet modern day glass art ...?
I've tried to cast a 15x21" piece of 1/4" starfire glass in a plaster/silica mold at 350-1250, hold 30, 60-1280, hold 30, then 9999 to 1450 ( and also to 1525), hold until I"m satisfied w. the cast (visual discretion).
The mold has vines on the bottom, the size of a small rope, and nothing on the top half of the mold. There were several small holes I drilled into the plster on the first try - still got a 7" diameter, and very beautiful, bubble. Like a setting sun on the horizon. Great, if it would fit into the grand scheme of the design...
I figured it was OK to use the mold again, which had broken apart from the first cast, and would have a lot of air that could move through the cast for gasses, and got the same result on the second try, at a higher temp (1525). Actually got some more bubbles after about 10 minutes (3 in total).
The mold is sitting on the bottom of the kiln, on sand, and bricked in on all sides. Should I move it off of the floor, so it may not be as much of a heat sink? I also used a pea-sized piece of glass in the corners to let the glass drape, so as to not catch air.
I'm beginning to run out of ideas....may have to turn to prayer....! .any help would be wonderful.
Jerry
I've tried to cast a 15x21" piece of 1/4" starfire glass in a plaster/silica mold at 350-1250, hold 30, 60-1280, hold 30, then 9999 to 1450 ( and also to 1525), hold until I"m satisfied w. the cast (visual discretion).
The mold has vines on the bottom, the size of a small rope, and nothing on the top half of the mold. There were several small holes I drilled into the plster on the first try - still got a 7" diameter, and very beautiful, bubble. Like a setting sun on the horizon. Great, if it would fit into the grand scheme of the design...
I figured it was OK to use the mold again, which had broken apart from the first cast, and would have a lot of air that could move through the cast for gasses, and got the same result on the second try, at a higher temp (1525). Actually got some more bubbles after about 10 minutes (3 in total).
The mold is sitting on the bottom of the kiln, on sand, and bricked in on all sides. Should I move it off of the floor, so it may not be as much of a heat sink? I also used a pea-sized piece of glass in the corners to let the glass drape, so as to not catch air.
I'm beginning to run out of ideas....may have to turn to prayer....! .any help would be wonderful.
Jerry