Tin Bloom?

I'm having some white areas developing at the edges of a float slump. The
white only shows at certain angles to a light source. Single thickness,
1200deg, at 400/hr, hold 20min. Slumping into a plaster mold
Is this tin bloom?
Any sujestions?
Liam
picture at
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Reply to
Liam
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Can't tell from the photo, sure its not devit? Why the slow ramp? and hold? how big is that piece? Doesn't look big. should be able to go faster to temp and no need to hold if the slump isn't radical, would avoid the devit.
Don't know how other people define it, but I look at devit as what happens when the glass is slow in an area where it "wants" to bend but isn't quite hot enough yet, and with float, 1200 qualifies.
Try this ramp, and I know I have no idea what kiln you use or if it will handle the program, but I just bent a bevel yesterday, 3/16 glass with 3/8 bevel, and it was not a radical bend, just a gentle curve. Bent it on a hydroperm mold and got very minor mold marks, had to look for them... 1200 deg per hour to 1265 then shut it off and leave it alone. no flash vent, nothing. no hold temp, nothing,,, this piece was about 9 1/2" long by about 4 1/2" wide.
Let me know how that works, keep in mind, the curve and weight of the glass, but 3/16 and DS are not that far apart in weight, but still a reasonable percentage that it should be considered. may have to go up 10-15 deg to get the same results, but if you start lower you can always do it again. ( I bend "test strips" alot to find temp/ time sets that work for something new.
Reply to
Javahut
Normally, devit will show white in most directions. It is the result of vitrified material (glass like) de-composing. It usually happens when glass is held at slumping temps for too long and the crash cooling from fusing and slumping temps is to reduce or avoid it. I am less familiar with tin bloom, but since tin only shows under certain lights and certain angles it sounds more likely. Your link only works when you are online, apparently.
Reply to
Mike Firth
Thanks guys. I'll try Java's suggestion first, since it seems to be the easiest solution. I talked to a float bender and he says he only gets this effect occasionally at corners. Since it only at the edges of the mold cavity where it makes a 20 degree angle from horizontal, this might may be the same problems he gets. He doesn't know what it either, but it's interesting that it only happens at corners. I might have to extend my mold so that it doesn't make a sharp angle.
My router keeps crapping out lately, or is it my DSL, I dunno.
Try the link again.
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Reply to
Liam

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