HNelson
08-27-2005, 12:15 PM
Has anyone slumped boro plate successfully without the sharpest area of slump devitrifying? I have a 1/8" thick x 8 .250" diameter plate I am slumping down on to a mold of Luminar sheet that is covered with shelf paper. The final shape is a taco. In the center all the way down through the glass is devitifying. The shape comes out perfect. I've trie 3 times.
1) ran to 1320 degrees f slumped let sit for 10 min. shut off
glass did not devitrify but had pitty mold marks.
2) ran to 1290 let sit 40min shut off
glass with little pitting but got the frosty down the middle
3) ran to 1275 let sit 45 min shut off.
No pitting but the frost down the middle.
I'm wondering if I should run to 1200 let it sit to soak even heat ,then ramp qucikly to 1350 shut down(with no saok and open the door for a quick cool to the annealing temp...
Any thoughts out there.
Someone suggested doing away with the shelf paper and coat the Luminar mold with a colloidal alumina..
......I'm stuck between pits and frost.....
Thanks for your help.
Heather
1) ran to 1320 degrees f slumped let sit for 10 min. shut off
glass did not devitrify but had pitty mold marks.
2) ran to 1290 let sit 40min shut off
glass with little pitting but got the frosty down the middle
3) ran to 1275 let sit 45 min shut off.
No pitting but the frost down the middle.
I'm wondering if I should run to 1200 let it sit to soak even heat ,then ramp qucikly to 1350 shut down(with no saok and open the door for a quick cool to the annealing temp...
Any thoughts out there.
Someone suggested doing away with the shelf paper and coat the Luminar mold with a colloidal alumina..
......I'm stuck between pits and frost.....
Thanks for your help.
Heather