Needle points or spikes when Slumping
- February 9, 2014 at 3:35 pm #10093
Recently I have been getting little needle points or spikes on my glass when I slump it into molds. This never happened before. I had not used my kiln or molds for a couple of years, I cleaned my molds very well and recoated them. Now for some odd reason when slumping into my molds needle points or spikes are forming on the edges. I use a Jen-Ken 15/6 Kiln with pre-programmed settings for fusing, slumping, tacking and fire polishing, which I have always done. I live in North Florida and the kiln is in my unheated garage. I work in the garage only on days where the temp is very near 60 degrees F or higher. I am using the wassabe plate 3-1/4″ x 1-1/2″ and a 5″ mini condiment bowl.
Can anyone explain what is causing my problem and tell me how to avoid this in the future?
DebbieFebruary 9, 2014 at 4:01 pm #13256wordanaParticipant
It would seem to me that perhaps you are slumping at too hot of a temperature. The glass should not be fluid enough at slump temps to cause spikes. Ditch the preprogrammed settings, and derive your own firing schedules.
In my kilns, I typically slump at 1225 deg F. You’ll have to experiment, as your thermocouple may be reading low if what “has always worked” no longer works.
You can knock the spikes off with diamond hand pads. With a light touch and a fine grit, it should be unnoticeable.
Jester’s Baubles Fused Glass DesignsFebruary 13, 2014 at 12:34 am #13257
Thank you for your reply. It was suspect that the temp might be running too hot but was not confident about changing it. What temp is good for fire polish – mine is set around 1200 deg F. When I fire polished a piece I was quite surprised it relaxed as much as it did.
Again, thank you for your input……
DebbieFebruary 13, 2014 at 3:26 am #13258wordanaParticipant
Fire polish is not the same as slumping.
Slumping temps are usually around 1225 degrees. Fire polish is at least around 1350 degrees.
Jester’s Baubles Fused Glass DesignsFebruary 15, 2014 at 7:24 pm #13259
I think I need a few lessons in glass fusing and the relationships of each type of kiln setting. Maybe I am reading my Jen-Ken kiln program incorrectly.
Where would you suggest that I go via internet to get accurate information regarding the different phases of glass fusing? I have been using my kiln as more of a beginner and would like to advance.
Your help and suggestions are appreciated.
DebbieFebruary 17, 2014 at 7:27 pm #13260TheMacdonaldParticipant
Right here, on this web site… https://fusedglass.wpengine.com/learn/technical_tutorials/glass_firing_schedules
TAMMarch 3, 2014 at 5:45 pm #13261katkramerParticipant
Debbie, I also agree that you’re slumping too hot.
Paul’s schedules here under the Tools section are very conservative firing schedules, and I’ve had consistent results. I’d also recommend them.
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