help with drop ring - WarmGlass.com

help with drop ring

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joan
Posts: 12
Joined: Thu Mar 20, 2003 4:07 pm
Location: maple ridge, BC

help with drop ring

Postby joan » Tue May 13, 2003 8:29 pm

I'm fairly new at fusing but decided to try a drop ring. I have a Skutt 1014 with controller. I first fused 2 layers (6 1/2 " diam) of system 96 . Then I used a drop ring with a 2" lip and a hole of 3". I elevated this on 3" posts. I used the preprogrammed slow slump, which is 300/h to 250 hold for 25 min, 300/h to 500 hold for 25 min, 300/h to 750 hold for 25 min, 600/h to 1150 hold for 5 min, 600/h to 1220 - at this point I checked to see if the slump was happening, it wasn't so I added 25 min to the hold at 1220. It started to slump a little but seemed to stop. I kept adding time up to 7 hours! but it slumped only a little (maybe 1 inch), then I added 20 degrees and it slumped a little more. I got tired after 9 hours and let the thing go to the anneal seg and cool down. I took it out the next day and it still had about 1 inch to go plus it had slight devit in some spots. I am guessing that my temp was too low. Can anyone give me a schedule for a project this size? How much time should I expect a project this size to take? Can I use super spray over the devit and put the thing back in the kiln to continue slumping? Help!
Joan :(

Jerry Barnett
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Joined: Wed Mar 12, 2003 11:40 am
Location: Texas, USA

Postby Jerry Barnett » Wed May 14, 2003 12:01 am

Joan, I composed a long reply, trying to help you understand the process instead of just supplying a different firing recipe than Skutt's. Unfortunately, when I went to post I got an "Invalid_Session" message and all was lost. I would send you a private post, but a private post to Christine, which took time to look up specific information, got the same treatment. So, if you are willing to send me a private message with your email address, I'll try to reconstruct the message. However, it will not be today.

Jerry

Bob
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Location: Salt Spring Island, British Columbia
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Postby Bob » Wed May 14, 2003 9:48 am

Hi Joan,

You have the patience of a saint! The approach you took works well, however I would suggest a change in your schedule. Molds have different slumping characteristics. So one schedule won't work for all molds. The slow slumping rate that you were experiencing is a great way to slump. You have the greatest control on the shape of the piece.

Here is the approach that I take. I ramp up at 300degF/hr until the glass starts to bend (generally about 1125 to 1150 F). I hold it there for 30 minutes. This allows the glass to conform to the drop through mold. I then raise the temperature 25F and hold about 15 minutes. I keep raising the temperature until the glass starts to slump at a slow but acceptable speed. It might move 1/2" in 30 minutes for example. Once I reach an acceptable temp I hold it there until the glass touches down on the kiln shelf. It generally takes my drop through pieces about 4 to 5 hours to slump.

As I mentioned, every drop through mold will behave differently. You are on the right track... just add more heat to speed up the process.

Hope this helps.

Cheers,

Bob

joan
Posts: 12
Joined: Thu Mar 20, 2003 4:07 pm
Location: maple ridge, BC

Postby joan » Wed May 14, 2003 3:52 pm

Thanks Bob,
I will follow your advice and try to do another drop ring project. A couple of other questions - the project I had problems with had slight devit. Could it have been due to the long hold time? And can I spray it with super spray and put it back in the kiln to continue the slump?
Joan

Bob
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Location: Salt Spring Island, British Columbia
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Postby Bob » Wed May 14, 2003 4:07 pm

Hi Joan,

In theory devit doesn't occur until above 1350F but the extra time may have been enough to allow the devit to develop.

Using a regular overglaze such as Super Spray or Spray A probably won't work. The curing temperature is much greater than the slumping temperature. It will either not melt or will leave a matte finish. There are overglazes made for slumping (e.g. Back Fire) that have higher lead content (I believe) and melt at lower temperature. They are intended for smoothing the back of a bowl during slumping. I don't know if they would leave a clear vitreous finish on the top surface. Intuition says that it won't work. I haven't used this product very much. Others with more experience might be able to comment.

Hope this helps.

Cheers,

Bob

Victoria Nelson
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Location: Townsvillle, Australia
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Postby Victoria Nelson » Wed May 14, 2003 4:16 pm

Yep, patience is a good thing with tall drop out creations.
The 'devit' you mentioned could be the result of the glass sort of picking up a very slight "texture" as the glass flows through the hole of the mold. Especially if the mold is fibre or the edge the glass flows through is not absolutley smooth and groove free.... or you've dusted with dry kilnwash. Good Luck and happy testing. Victoria

Brad Walker
Site Admin
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Postby Brad Walker » Wed May 14, 2003 5:03 pm

Bob wrote:There are overglazes made for slumping (e.g. Back Fire) that have higher lead content (I believe) and melt at lower temperature. They are intended for smoothing the back of a bowl during slumping. I don't know if they would leave a clear vitreous finish on the top surface.


They don't. My experience is that the finish is matte or hazy -- not necessarily unattractive, but certainly not as shiny as firepolished glass.

joan
Posts: 12
Joined: Thu Mar 20, 2003 4:07 pm
Location: maple ridge, BC

Postby joan » Wed May 14, 2003 7:58 pm

Thanks everyone for your help. I think I'll just start a new bowl. The one I had problems with wasn't that nice to begin with so it's no great loss.
Joan


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