Needle points or spikes when Slumping
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- This topic has 6 replies, 4 voices, and was last updated 6 years, 11 months ago by
katkramer.
- AuthorPosts
- February 9, 2014 at 3:35 pm #10093
debz48
ParticipantRecently 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?
Regards,
Debbie
February 9, 2014 at 4:01 pm #13256wordana
ParticipantIt 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.
Dana W.
Jester’s Baubles Fused Glass Designs
February 13, 2014 at 12:34 am #13257debz48
ParticipantDana W,
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……
Debbie
February 13, 2014 at 3:26 am #13258wordana
ParticipantFire polish is not the same as slumping.
Slumping temps are usually around 1225 degrees. Fire polish is at least around 1350 degrees.
Dana W.
Jester’s Baubles Fused Glass Designs
February 15, 2014 at 7:24 pm #13259debz48
ParticipantI 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.
Regards,
Debbie
February 17, 2014 at 7:27 pm #13260TheMacdonald
ParticipantRight here, on this web site… https://fusedglass.wpengine.com/learn/technical_tutorials/glass_firing_schedules
TAM
March 3, 2014 at 5:45 pm #13261katkramer
ParticipantDebbie, 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.
: )
Kat - AuthorPosts
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