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Found 6 results

  1. Hello all, Looking for firing schedules. I have a small manual electric kiln with a kiln sitter and wondering if anyone has a simple, clear firing schedule they follow and could share? I am a beginner trying to learn how to fire for Cone 04 Bisque and then another schedule for Cone 6 Glaze Fire. I am using buff stoneware. Any firing tips appreciated! Thanks so much, Natalie
  2. Educational Post Firing Schedule Variables There are several key issues that effect the final firing schedule selected. 1. Functional or Non-functional use. 2. Wall thickness: thrown or hand built up to 3/8". Structural starting at 1/2" up. Sculptural with varying thickness/ parts. 3. High iron/ carbon bodies vs. white body. 4. Single fire vs. bisq. For the bulk of most firings; functional or non-functional and single fire vs. bisq fire comprise most firings. The additional variable is how thick are these pieces? Several universities across the world have done studies using X-ray defraction to measure heat work in gradient kilns. The general consensus being that it can take up to 30 minutes for the atmospheric temperature to reach the core of the clay body in the 3/8 to 1/2" thick range. In order for clay to fully mature, this variable has to be included in the firing schedule for functional wares. Absorption rates increase, COE values can change and firing defects such as pin holing, blistering, and shivering can be attributed to firing schedules. Sodium (Nep Sy) is the flux of choice in the USA and Canada; and is commonly used in other parts of the world. It is a cheap body flux but it does create issues. Sodium begins to melt at 2044F, and potassium at 2012F, as the clay is converting from spinel to mullite at 2050F. In application; at the same time sodium begins to off gas vigorously, the porosity of the clay is beginning to close up. Extending the time climbing to peak temperature allows the feldspars to completely off gas; thereby resolving pin hole issues while maturing the clay. Selecting a preset ramp speed or programming your own depends upon the clay body, piece size, weight, and foot ring contact. In addition, starting at single fire or from bisq also decides ramp speed. Pieces with wall thickness above 3/8", heavy pieces above 7lbs, or pieces with large shelf contact such as platters need slower ramp speeds to allow for even heat distribution. Slower speeds during the quartz inversion range is also advisable for large format pieces Quartz inversion occurs at 573C (1064F) when quartz changes from alpha to beta phase. Silica (quartz) actually expands at this temperature: part of an exothermic reaction. Just prior to this phase change and to just above this temperature: molecular moisture is being driven out of the body resulting in overall shrinkage. These two processes are occurring relatively at the same time: overall shrinkage from the loss of molecular moisture, while silica is expanding during inversion. If pieces are heavy enough, have weight, or have large shelf contact such as platters: cracking can occur. The remedy for this issue is programming a 100F per hour climb from 1000 to 1100F before resuming higher ramp speeds. You can actually increase firing speed to 180 to 270F an hour if firing porcelain or white stoneware. The overall size and weight of the piece may still justify a slow ramp cycle once you pass the inversion temperature range. Wadding, sand, or alumina may be placed under large/heavy pieces to facilitate movement during the firing cycle. Dark and red bodied stoneware produce buff, terra cotta, and brown bodies that potters love. While they produce warm toasty colors, those colors come from iron disulfide. (Pyrite) in addition, lignite coal particles are common contaminants. Both sources of sulfides require special firing cycles to prevent blistering, bloating, and carbon coring. Inorganic carbons burn off from 1250 to 1750F, and require heavy oxidation during this temperature range. Rather single firing or bisq firing: programming a slow cycle of 108F an hour (slow speed) from 1250 to 1750f an hour while oxidizing the kiln is required. If single firing; you are simply programming a bisq fire, while incorporating the final ramps to peak temperature. If firing large, heavy, or large foot ring pieces: then adding a quartz inversion cycle is required. If firing dark or red bodied stoneware; then programming a slow ramp (108F) from 1250 to 1750F while oxidizing the kiln is required to avoid blistering, bloating, and coring. Once you reach 1800F in a single fire, then you can increase ramp speed to 180 to 270F until you hit 2050F. At this temp, speed is then reduced to 108 to 125F an hour to allow escaping spars to escape before the clay body vitrifies. University studies from around the world all report an endothermic reaction at 2050F as observed by X-ray defraction. It is a key reaction temperature in the firing cycle; when the porosity of the body begins to close rapidly. Most clay bodies in the USA and Canada use Nep Sy (sodium) as a body flux. At 2044F, sodium becomes reactive and off gasses vigorously; which appears as pin holes in the glaze. Rather single firing or starting from bisq; slow ramping from 2050F to peak hold allows the extra time for off gassing spars to dissipate. Recommended ramp cycle from 2050 to 2232F is 108-125F an hour. A commonly used peak temperature is 2190F with an extended hold (cone 6 ), use the recommended ramp cycle for this program firing. This slow ramp cycle towards peak range also has the added benefit of extending element life. Tom
  3. I recently purchased an old Gare ( or Evenheat) Kiln model 2327. Evenheat still makes this high fire kiln but, when I searched their website they only provide a manual for their newer model of the 2327. I am looking for the manual pertaining to the older model 2327. the kiln I purchased is equipped with a kiln sitter model LT-3K which has a timer dial as well. the controller uses a series of 6 (on/off) switches to control which elements are heated, I am also looking for a firing schedule for these switches. If you have any tips or suggestions on operating and firing this kiln please feel free to add to the conversation. Any bit of information is helpful. Thanks all!
  4. So I was thinking about glazes and I fire my kiln at 108F/h to cone 5 and hold for 60 minutes. This got me thinking about trying orton's other rate of climb. Trying something like 27F per hour to cone 6 instead of using a hold at cone 5. So fire to 2111F, 1965F then climb to 2165F at 27F/per hour. I was wondering if anyone has tried this type of schedule? I am curious at the differences it would make in my glazes. Instead of going straight cone 6, changing to cone 5 with an hour hold improved my glazes a lot. It got me thinking about trying this. Anyone fire at that final rate of 27F/h? Did it improve your glazes or no change?
  5. I've just opened my first firing with Hesselberth/Roy's suggested firing schedule for cone 6. I was surprised to see that my glazes turned out way more matt than usual (see photo of two pots, same glaze) as well as having a complete color change with my layered blue. Has anyone else experienced a complete change (for the worse) when using this firing schedule. I've rechecked the programing and it was entered correctly. Maybe having 3" brick on my kiln changes the game??? Would love some input. I'm refiring this load and hoping to salvage it.
  6. I have a new Paragon Kiln TNF-82 with a 12 key Sentry digital controller. I am so very confused as to the firing schedules. Ie. ramp up. Cool down etc. I used to own a manual kiln with a kiln sitter. I just put the bar in and it shut off when done. Now, can I fire the same way, or do I need to do a ramp up and slow cool? I am firing 12 x 12 x 1/2" tiles. First to bisque, then to ^6. I plan on stacking 4 on each shelf as suggested by an expert to bisque. Do I need to slow cooling down? Does anyone have a firing scedule for bisque and glaze firing I could follow? Its taken 3 weeks to dry these tiles, (46) and I really hate to see them mess up because I did something stupid! I have read all over the internet and have bought several books, but am still so confused!! I am sure i will learn and love my new digital, but right now it's very intimidating!!! Please help!! Please!!! Thank you Linda
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