Page 1 of 1
Edge Hazing when slumping BE w/Uroboros clear cap
Posted: Fri Apr 11, 2003 1:50 pm
by Andrew
I have been making thick plates (2-4 layers) of bullseye using a clear cap of 90 Uroboros. They are clear and shiny when fused as a flat plate, but when slumped develop a haze along the 1 to 1.5 inch outside margin. I usually ramp at 600 dph but have gone as low as 400 dph with the same result.
Any suggestions?
Posted: Sat Apr 12, 2003 1:00 pm
by Lani McGregor
Andrew,
I assume that you are slumping with the same surface up (the clear cap) as was up in the fuse cycle, yes?
What is the shape of your slumping mold?
Does it have steep walls?
Is it possible that as the fused blank drops into the mold it is sliding down the mold surface, disturbing the shelf primer causing a dusting around the perimeter of the glass? Any kind of dust or powder that settles onto the glass can nucleate devitrification.
Just guessing without knowing the whole story.
What's your slumping cycle?
L
PS Is the “90 Uroborosâ€
Posted: Sat Apr 12, 2003 1:18 pm
by Cynthia
This may not help you with your riddle, but I have been using machine rolled URO 90... made by Spectrum. BE machine rolled was also made by Spectrum, but because of devit and haze problems, BE quit having Spectrum manufacture this glass for them (or so I am told).
I never had problems with the BE machine rolled, but when I ordered my last shipment of glass, I had to take the URO 90 machine rolled as the BE machine rolled wasn't available anymore. Some, but not all of the machine rolled glass would devitrify or get scummy with a noticeable banded repeating pattern to the devit, like roller marks. I ran into trouble when I would fire first with the clear glass shelf side, then fire again with the clear glass up. It was on this second firing that the devit, or contamination would show up. I found no remedy except for to sandblast it off. The up side is that I discovered and love the matte finish you can create by sandblasting and refiring...but that doesn't really help you.
That may or may not be what you are experiencing. But worth considering to see if it is a fit.
The other thing I wonder is if you are grinding your edges before slumping. The ground edge, particularly if you are using a rough or fast bit type of grinding surface will not polish up nicely, but will look scummy. If you are grinding and using a rough grinding surface, do a final pass on the surface you ground with a fine grinding surface. You will get better, more posished results.
I have a disc grinder and I got a rough grinding surfaced diamond disk to remove more material faster. Once I swithched to that disc, I started getting scummy edges. Switched back to the finer grinding surface...no more scummy edges.
Just some things to consider.
Posted: Sun Apr 13, 2003 10:18 pm
by Andrew
[quote="Lani McGregor"]Andrew,
I assume that you are slumping with the same surface up (the clear cap) as was up in the fuse cycle, yes?
What is the shape of your slumping mold?
Does it have steep walls?
Is it possible that as the fused blank drops into the mold it is sliding down the mold surface, disturbing the shelf primer causing a dusting around the perimeter of the glass? Any kind of dust or powder that settles onto the glass can nucleate devitrification.
Just guessing without knowing the whole story.
What's your slumping cycle?
L
PS Is the “90 Uroborosâ€