Potters & Sculptors - Making Rock from Mud
As you can see, the blistering was pretty severe, and was present in all the pieces with this glaze combination. There was one blister in one of the mugs where only the Nutmeg glaze was located."
The following were moved from General Comments on the Single Firing Group main page to this discussion topic where they belong. Please take no offense. This is just me acting in an editorial role to try to maintain a degree of organization on the network.
Comment by George Lewter just now
Re: Kathy Ransom's question, "I know that I need to go slow until at least cone 06 and I wonder if I need to go slow again on the cool cycle?"
After carbon burnout on heating up (1400 deg F to be on the safe side), you can complete your firing on your regular firing schedule, for at this point there is no longer any reason for a difference between single firing and glaze firing on bisque ware. Put another way, cooling depends on what glaze effects you are going for, rather than something different about single firing.
I'm doing a single fire today with my new Orton controller - No constant messing with knobs! This is a mixed load with Steven Hill and other glazes. My program for today is: (Temperatures given in Fahrenheit)
150 deg./hr to 220 deg. and hold for 1 hr (preheat)
200 deg./hr to 1400 deg.
100% power to 2145 and hold for 1 hr. (My kiln is underpowered and only gains temp very slowly at the top so I reduced max temp 15 deg.)
0% power down to 1700 deg.
100 deg./hr down to 1400 deg. and hold for 1 hour.
Currently I'm at the maximum temperature 1 hour hold and I'm thrilled to see the controller holding to within 1 degree plus or minus of my set temperature of 2145. I never have achieved that tight of control when trying to hold manually.
This is my current firing schedule for newly glazed and still damp ware. I'm currently using Laguna B-mix 5 clay. I have had no body defects in my recent firings. (Units are in degrees farenheit)
Ramp up 100/hr from room temp to 220. (With kiln top propped open, peep hole plugs out, vent on)
Hold at 220 for 2 1/2 hrs.
Ramp up 200/hr to 1400 - No hold here. Close kiln (lid and peeps) around 800 & make sure vent is running negative pressure inside kiln (should pull smoke into kiln at a small hole in the lid)
Ramp up at full power to 2140 (Use cones to adjust this temperature setting for your kiln to achieve cone 6 after your one hour hold. Your kiln/pyrometer/controller combination may necesitate a considerably different maximum/hold temperature) This schedule gave me cone 6 touching down and cone 7 starting to bend.
Hold at 2140 for 1 hour.
Ramp down at free fall to 1750. You may want to slow this ramp for matte glazes to have time to crystalize out.
Hold at 1750 for one hour. I use this hold for iron red color development.
Kiln off and free fall to room temperature or cool enough to unload.
This is the Steven Hill firing schedule copied from the Oregon Potters Association newsletter from Feb-March 2011. It is probably outdated as he tweaks that kind of thing very often, but it gives you a place to start. It is NOT CAST IN STONE!
STEVEN HILL'S FIRING SCHEDULE: Steven Hill, as you may be aware from his ads for Skutt Kilns, has recently begun firing his work in electric kilns. He is know for his raw glazing (not bisquing his work prior to glazing). The following schedule is used in his Skutt 1027 kiln. Temperatures are degrees F.
Ramp: End Point: Hold:
1 200/hr 220 1-3 hrs, depending on wetness/ thickness of work
2 100/hr 500 0
3 400/hr 2100 0
4 100/hr 2180 1 hr, according to Skutt manual this end point is cone 5, but with 1 hr soak cone 6 falls
5 9999/hr 1700 0
6 50/hr 1600 30-60 minutes, then cool naturally
“As of 10/10, this is my schedule for a ^6 single firing of greenware. Nothing is static with my firing schedules, however, so it will most likely change in the future. One thing is certain… there is no sense in extending the firing beyond what is necessary for desired results, as this is wasteful of electricity. As I do further experiments, I will work on shortening the firing cycle.” Steven also mentioned that he was constantly changing his cooling cycle, and would probably never settle on one particular cooling schedule. He is working on an article, probably for Ceramics Monthly, about his new electric firing techniques.
His probably schedule for a firing of bisqued glaze ware is:
Segment: Ramp: End point: Hold:
1 200/hr 220 30 minutes, this is only necessary if you have raw cone packs
2 400/hr 2100 0
3 100/hr 2180 1 hr, according to Skutt manual this end point is cone 5, but with 1 hr soak cone 6 falls
4 9999/hr 1700 0
5 50/hr 1600 30-60 minutes, then cool naturally
once you have hit cone six and the cone sitter is triggered... are you simply leaving the kiln to cool on its own or are you down firing in some manner?
I'm in the same boat as you, my kiln is loaded all I need to do is fire it.... sooner than later!
It's an old thread, but thought I'd add my 5 cents anyway ;)
On the initial stages of a once fire, the 'drying out' phase, I personally try to stay clear of having a precise time in mind. Yes, good to know for planning (will it finish before I'm too tired to stay awake !?) .. but inaccurate in reality.
Different kilns, different loads, different pots, different weather ... all lead to variations.
Think of the 'reason' you are holding the temperature, it is to let all the water out of the clay/glaze before moving onto the high temps where it would otherwise cause explosions.
Hence, try to only move on from the initial drying temperature when the water has indeed finished escaping, for fact.
A cold piece of mirror/steel held over the vent of your kiln for a second or two, will mist up and be wet to the touch when the water is being pushed out.
Doing this at regular intervals during the drying stage, you will also get a good feel and connection with what is happening inside, you'll see it being lite, become heavy and saturated, and yes eventually decline.
It's a nice feeling to be 'in touch' with the physical events rather than simply watching the hand on a clock.
Yet most importantly, you will know 'for sure' when it is good and safe to ramp up to the next temp.
I could go on and on, but try to connect with your kiln in a similar fashion at other stages of the cycle.
Yes you will need a time schedule in the early days just starting out, but with time you will be able to judge for yourself how to tweak for individual circumstances.
Look through the spyhole and note when the atmosphere becomes hazy, when clear, the textures and reflectance of the glazes.
Anyway, I'm rambling now !
.. happy firing :)