When it rains, it pours... - WarmGlass.com

When it rains, it pours...

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skin_mechanic
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When it rains, it pours...

Postby skin_mechanic » Sun Apr 11, 2004 9:39 pm

...I decided to do a full fuse today with several pieces that I worked on yesterday, including the Dali portrait prototype. I have 4 shelves stacked in the kiln. On the top shelf were 2-19" float glass disks with frit powder and some antique gold mica sandwiched betwixed the two. Anywho, I soaked the pieces at 1500 for 20 min, looking in the peep holes every few minutes. After seeing what I thought was a full fuse, I hit the "anneal now" button and started to crash vent the kiln. When I opened the lid, I damn near had a stroke. Not only did the glass disks NOT fuse, but the top disk liquified and the majority of it ran off the bottom disk, pouring off the kiln shelf onto the kiln floor. The frit powder and mica didn't even fuse to the bottom disk. I don't understand how this happened, how it's possible for glass NOT to stick to itself... I'm kinda in a state of shock :shock: :shock: :shock: :shock: Thank God I put multiple coats of kiln wash on the kiln floor.

Brock
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Re: When it rains, it pours...

Postby Brock » Sun Apr 11, 2004 9:49 pm

Sounds like you must have had a thick layer of mica separating the glass discs. Spray on multiple thin coats, and put it on the surface, of the top blank, or leave a glass to glass rim on both blanks if you encapsulate it. The glass and mica don't really fuse, at the right temp the glass will become viscous enough to "grab" the mica. Same for metal foils. Brock


Skin_Mechanic wrote:...I decided to do a full fuse today with several pieces that I worked on yesterday, including the Dali portrait prototype. I have 4 shelves stacked in the kiln. On the top shelf were 2-19" float glass disks with frit powder and some antique gold mica sandwiched betwixed the two. Anywho, I soaked the pieces at 1500 for 20 min, looking in the peep holes every few minutes. After seeing what I thought was a full fuse, I hit the "anneal now" button and started to crash vent the kiln. When I opened the lid, I damn near had a stroke. Not only did the glass disks NOT fuse, but the top disk liquified and the majority of it ran off the bottom disk, pouring off the kiln shelf onto the kiln floor. The frit powder and mica didn't even fuse to the bottom disk. I don't understand how this happened, how it's possible for glass NOT to stick to itself... I'm kinda in a state of shock :shock: :shock: :shock: :shock: Thank God I put multiple coats of kiln wash on the kiln floor.
My memory is so good, I can't remember the last time I forgot something . . .

Bert Weiss
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Postby Bert Weiss » Sun Apr 11, 2004 10:34 pm

Mica doesn't stick as well to float glass as it does to BE. I like to mix the mica with Sunshine series Flux (clear glass enamel) any flux should work.

I do not fire hotter than 1420 to fuse float glass. I do soak there for 20 - 40 minutes.

I have noticed that radiant heat from the elements goes through a layer of clear float glass and heats whatever is beneath it first. The mica got hot, did not stick much and the top glass, when the top glass got hot. it flowed off of the mica.
Bert

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skin_mechanic
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Postby skin_mechanic » Sun Apr 11, 2004 10:44 pm

I only sprinkled the mica powder in a coupla small areas near the center, as an accent. The majority of the top disk was resting on the Uroboros frit powder, several different colors in parallel bands. I don't see why the top disk would have such a drastic change in viscosity, while the bottom disk kept it's shape. Note: my Skutt doesn't have elements in the lid.

Phil Hoppes
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Postby Phil Hoppes » Mon Apr 12, 2004 12:21 am

Don't stack the shelves. There are very few glass projects that work stacked. The top will heat too much even if there are not top elements and your bottom shelves won't do much of anything at all as the heat differential between top and bottom will be too great. With 4 shelves in there you created baffles for the heat which caused a great deal of temperature differential. The kiln you have is really a ceramic kiln. Not that it won't work with glass, it will but you should not stack the shelves. Figure one project at a time, one step at a time.

Phil

Lynne Chappell
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Postby Lynne Chappell » Mon Apr 12, 2004 1:42 am

The way you describe it doesn't sound possible. Very likely, the top shelf was a lot hotter than the rest - when you were peeking, you weren't looking at that shelf, were you?

However, if both disks were the same glass, one shouldn't liquify while the other holds its shape. Is it possible that the top disk had a little thermal shock experience and blew apart with enough force that it ended up on the floor of the kiln?

rosanna gusler
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Postby rosanna gusler » Mon Apr 12, 2004 7:57 am

i always use at least 3 shelves in my kiln. as long as the bottom one is above at least one ring of elements it is pretty even. to stack shelves soaks are the key. i soak around 1100 for 20-30 min for evenivity and then soak at process temp (different temps for different projects) untill done. is it possible that your mobile disc shifted before melting temps? powders and such can act like little ball bearings. i have looked in and seen the glass waterfall in progress. in my case it was from pieces shifting before fuse temps. maybe you should do a kiln load of tests. cut a bunch of squares or whatever, place them evenly on your shelves, make notes about each shelf, fire. do not open the kiln without a notebook in hand. take notes about what happened. you could make a kiln load of kiln carved suncatchers or something if you did not just want to fire stacks of glass. rosanna

Phil Hoppes
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Re: When it rains, it pours...

Postby Phil Hoppes » Mon Apr 12, 2004 8:54 am

Skin_Mechanic wrote:.
... mica didn't even fuse to the bottom disk.


On the mica's, I believe you need to fuse them first to the surface. Not sure what they are going to do sandwitched between layers before first being fused into the glass. Also, if you layered the mica such that it covers the first layer of glass fairly evenly the second layer will not fuse to the first. The mica is going to act as a barrier between the two layers of glass. This is the same as irid coatings. If you fuse irid side to irid side you need to have places where you are fusing glass to glass otherwise they will not fuse at all. On the stacking, It is difficult, not impossible, to make that work. I've tried stacking with no luck. I got glass to fuse on the top and nothing on the bottom. I soaked for more than an hour at 1260 to even things up and made sure I had an equal number of elements between each shelf. I do however have top elements which is probably the reason for the difference. Anyway, like Rosanna said, if you really want to stack, you need to do some tests first. Also if you have access to a pyrometer or temperature probe and can get a thermocouple in between your stacked shelves for measurement during a cycle it would prove very benificial. If you can't get access to a thermocouple go to the BE connection website and download the "knowing your kiln" technotes. Here is a link:

http://www.bullseyeconnection.com/pdfs/ ... tes_01.pdf

Follow their tips and it will help you characterize your kiln. You may want to download their other tech info. I think you will find it usefull.

Phil

Bert Weiss
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Postby Bert Weiss » Mon Apr 12, 2004 8:59 am

Uroboros frit is not compatible with float glass so your piece was destined for doom.

If your Skutt is controlled by one thermocouple, the temperatures inside vary widely, hottest on top. Some Skutts are controlled by multiple thermocouples, one for each ring. this is a better scheme for evenivity. Whatever your setup, you will have to learn it's idiosynchroncies and act accordingly.
Bert



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skin_mechanic
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Postby skin_mechanic » Mon Apr 12, 2004 9:24 pm

I pulled the projects outta the kiln when I got home from work. Everything fused as expected, no problems with the float glass or frit powder, except the glass disks, and the puddles of glass lifted off the kiln floor without effort. I did get some interesting vit patterns on a piece of scrap glass that I included with decorative foil, but that's another story. Per ya'lls suggestion, I'll try to be less ambitious about cramming the kiln with shelves, though it's kinda hard to resist that temptation when I look at the power bill :shock: I hate to waste electricity on 1 or 2 projects when the kiln has the capacity to hold much more. I guess I need to learn moderation... I'm still clueless about why the bottom disk didn't melt. There was no deformation around the glass' circumference, but it did soften enough to pick up some texture from the kiln wash.

Bert Weiss
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Postby Bert Weiss » Tue Apr 13, 2004 7:16 am

Skin_Mechanic wrote:I pulled the projects outta the kiln when I got home from work. Everything fused as expected, no problems with the float glass or frit powder, except the glass disks, and the puddles of glass lifted off the kiln floor without effort. I did get some interesting vit patterns on a piece of scrap glass that I included with decorative foil, but that's another story. Per ya'lls suggestion, I'll try to be less ambitious about cramming the kiln with shelves, though it's kinda hard to resist that temptation when I look at the power bill :shock: I hate to waste electricity on 1 or 2 projects when the kiln has the capacity to hold much more. I guess I need to learn moderation... I'm still clueless about why the bottom disk didn't melt. There was no deformation around the glass' circumference, but it did soften enough to pick up some texture from the kiln wash.


Less mass in the kiln does cost less to reach temp.

A fiber kiln costs less to fire than a brick kiln.
Bert



Bert Weiss Art Glass*

http://www.customartglass.com

Furniture Lighting Sculpture Tableware

Architectural Commissions


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