haze (devit?) on glass what is wrong with schedule

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chrisk
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Joined: Tue Nov 04, 2008 12:45 am

haze (devit?) on glass what is wrong with schedule

Post by chrisk »

I've used two schedules (the second one I slowed down on) but still having hazing problems - actually the second schedule gave me more haze on all my Bullseye transparent deep royal #1114.
First schedule 2nd fireing
300 - 500dph -2min
chrisk
Posts: 13
Joined: Tue Nov 04, 2008 12:45 am

Re: haze (devit?) on glass what is wrong with schedule

Post by chrisk »

Drat it is late and I hit the wrong key before I finished typing.

In reading the board I also noticed several people anneal by going Full to 960, the 100 to 800 and last 200 to 700. Why the last two steps instead of one.

First fireing 2nd firing
Ramp / dph/ hold
300 - 500 - 2 300 - 500 - 2
500 - 1150 - 5 300 - 1100 - 5
325 - 1225 - 50 50 - 1250 - 50
400 - 1480 - 10 300 - 1460 - 10
Full - 900 - 1hour Full - 900 - 1
100 - 700 - 2 100 - 700 - 2

Chris
Marty
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Re: haze (devit?) on glass what is wrong with schedule

Post by Marty »

I can't make any sense of your schedule but what are you firing and what are you using for a separator?
chrisk
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Re: haze (devit?) schedules clarified

Post by chrisk »

Marty - I am firing on mullite shelf that is washed with HotFire and I used Papyros (which I have been using successfully in my smaller kilns.
I meant for my schedule to be 2 columns but they merged so here are the schedules I used for the first and second firing. The devit is mainly on the BE Blue 1114 and less on the black. Actually had more devit on the blue in the second fire.
First firing schedule.
amp / dph/ hold
300 - 500 - 2
500 - 1150 - 5
325 - 1225 - 50
400 - 1480 - 10
Full - 900 - 1hour
100 - 700 - 2

2nd Firing schedule with slower schedules
300 - 500 - 2
300 - 1100 - 5
50 - 1250 - 50
300 - 1460 - 10
Full - 900 - 1hour
100 - 700 - 2
Marty
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Re: haze (devit?) on glass what is wrong with schedule

Post by Marty »

I'm not going near those schedules (I'm all out of rant) but if it's haze and not devit I'd suspect the papyros- I get it sometimes from fiber paper and sometimes from thinfire.
Morganica
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Re: haze (devit?) on glass what is wrong with schedule

Post by Morganica »

Unlike Marty, my rantishness is largely untapped today, so...I'm not sure of the reason for all the segments and holds in your schedule. Why 300dph to 500 with a 2-minute hold? What is supposed to happen at that point? The glass is pretty vulnerable between 500 and 800F or so...so why go faster there? (and again, why the hold?)

Each segment in a firing schedule should be intended to do something specific to the glass, and unless you've got a controller that requires a hold at every segment, only put holds where a prolonged time at that temperature will change the glass or prevent something. Zooming to a goal temperature and then holding there to reach thermal equilibrium is kinda like zooming through a stop light and stopping twice at the next light to make up for it. Better to spend the hold time in getting to your goal temperature.

Haze-wise, if that's devit you would expect it to be worse on the second firing--the crystallization of the glass is spreading. It'll keep growing; it needs to be removed or covered up if you want to eliminate it in the next firing. I've heard that Papyros doesn't exacerbate devit the way other fiber papers can, but I haven't tried it so I can't say if it does or not.

Personally, I only use fresh fiber paper in the kiln when I know I'll be coldworking the glass coming out of that kiln. If I'm in a final firing, no fiber allowed, and I make sure that all kiln washed surfaces in the kiln have had at least one previous firing. And I vent to about 900 or so.
Cynthia Morgan
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