[ATM] A Successful Experiment

[vorblesnak@peak.org]

I have a friend locally with a small glass kiln.  I got her to try the
plaster as a slumping tool material experiment and it worked.  I had been
told that plaster would not stand up to the heat of a slump.

The tool was plain plaster of paris, cast and ground to the right curve
for a telescope mirror.  6 and 1/2 inches in diameter by 1 inch thick.  I
let it dry for 30 days and then passed it on to her for the slump.  The
glass was an orange filter, 5/16ths inches thick by six inches in
diameter, probably BK7 optical glass.  I got it from Surplus Shed on the
internet.  She took it to 1300 degrees, soaked for 2 minutes and then
turned the kiln off.  No soak at strain point or at anneal.  The curve is
good to the plaster.  The plaster cracked down to about half it's
thickness but is still intact.  The slumped glass has some rough spots
from the plaster but nothing major.  The edge zone is where all the
roughness is, the center is remarkably smooth and clean.  I suspect the
plaster cracked at the edge first and that was where the glass was
softest.  No big deal, it will grind off in a heartbeat, or two.  It
appears that plain plaster will work for a one shot slump.

David Davis
Toledo, OR 97391





_______________________________________________
ATM mailing list http://www.atmlist.net/