No slumping detail?
- April 17, 2014 at 1:11 pm #10136
i have been fusing at workshops for years but just got my own kiln. That changes everything doesn’t it!
I have been using a the preprogrammed standard slumping schedule in my Bonnie-Glo Fiber kiln:
R 1 300 to 1000 Hold 0
R 2 700 to 1200 Hold 35
R 3 FULL to 960 Hold 30
however, I am not getting any of the mold detail in my slumps. For example I have a shell shaped mold and while I do get a nice slump it doesn’t go into the bottom of the shell swoops. What can I do to change that schedule to increase the detail going into the slump?
Also, about the forum– is there a search feature? I thought of searching old threads to see if anyone else had asked this question but I didn’t see a search field. Am I missing it?
thanks for any help, KatApril 17, 2014 at 5:13 pm #13328CJAlexParticipant
Are there any holes in the mold to allow air to escape? If there are holes, are they blocked by the mold being on your kiln shelf? I always raise my molds up on short kiln posts, being careful to not block any of the holes.
ConnieApril 17, 2014 at 6:45 pm #13329wordanaParticipant
Increase the hold time or the temperature. The time it takes to slump a piece depends upon the size of the glass and the span of the hole that the glass is slumping into. Smaller mold = smaller span = longer hold and/or higher temp. Personally, I slump at 1225, though some people slump at 1100 — just depends upon the mold.
My next advice is to dump the preprogrammed schedules and learn to program the kiln based on what you are doing. In fusing, one size does not fit all. Start with the schedules found on this site, and then adjust for your kiln. Keep a log book of firings.
Jester’s Baubles Fused Glass DesignsApril 17, 2014 at 10:37 pm #13330
Yes, the holes are clear. I will try to increase the temp first since the hold is already 35 min.
I’d prefer not using the schedules usually suggested for a brick kiln in my fiber kiln. I know I could use those traditional schedules but that would be a waste of both time and electricity in this kiln so I am hoping someone else has used a fiber kiln and has experience with schedules. I am keeping a log of all firings.
Thanks, katgApril 17, 2014 at 10:57 pm #13331wordanaParticipant
I think you misunderstand kilns and firing schedules. A ramp rate is a ramp rate, regardless of whether you are firing in a fiber kiln or a brick kiln. If I set a schedule to ramp at 300 degrees per hour to 1100 degrees, they will both fire at the rate of 300 deg/hr, it is just that the fiber kiln may likely use LESS energy to get there, since it has less thermal mass (i.e., no bricks) to heat up. Conversely, when dropping down in temp, a rate of descent of 100 degrees per hour is still 100 degrees per hour. The fiber kiln, having less thermal mass, will lose heat a little more quickly (so you’ll need MORE power than in a brick kiln), but the controller will still attempt to make sure the temp descends at 100 deg/hr.
A firing schedule (ramp rates, process temperatures & hold time) is based on the glass project — not kiln construction. The only place kiln construction even slightly comes into play is with accuracy of the thermocouple inside the kiln (e.g., if your thermocouple reads 25 degrees hotter than it actually is, you’ll need to program for 25 degrees cooler).
Jester’s Baubles Fused Glass DesignsApril 18, 2014 at 12:19 am #13332CJAlexParticipant
How deep is the mold? It would help if I had a better idea of what the mold looks like.
What COE glass are you using? Opaque? Transparent? It makes a difference.
Bullseye will typically say it’s safer to add time rather than increase the slumping temp. However, it’s also better to not go above 1200 if holding for a long time. When I have a long hold for a stubborn slump, I set my top temp at 1190 (also recommended by Bullseye). I’ve held it there as long as an hour. If you keep the temp this low, you shouldn’t have any problems with a long hold.
I have a fiber kiln, and the only variation I need to make in standard firing schedules is the cool down phase after annealing, particularly if I am creating a piece that is thicker than the typical 6mm (1/4 inch). Letting the kiln cool as fast as it can is too fast in a fiber kiln in many cases. Also, if using Bullseye glass, the current recommended annealing temp is 900.
All the temps I mentioned are different if you are using COE 96.
I hope I didn’t add confusion to all this.
ConnieApril 18, 2014 at 12:33 am #13333
You are both right about misunderstanding schedules. I keep getting different information from everywhere I go for advice. When I got my kiln at Jen-Ken, mike went through the most used schedules for the fiber kiln but of course there are several variables that cause the standard schedules not to be appropriate.
His suggestions use a quick ramp–as much as 1000/hr– and minimal annealing segments for fusing. I have found his schedules to be fine for fusing but his slumping schedule seems to be much more dependant upon the variables of mold, glass type, size and thickness. I will keep experimenting.April 26, 2014 at 9:24 pm #13334Stephen RichardParticipant
Can be achieved by a combination of a number of things. For example, you could use 300F ramp all the way up as fast increases in temperature do not allow the whole of the glass to soften adequately. You can also extend the soak time. You can increase the temperature. But slowing the rate of advance is most often the best solution.
Stephen RichardApril 26, 2014 at 9:28 pm #13335
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