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David Woodin

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Everything posted by David Woodin

  1. Firing to cone 4 with a soak of 45 minute's will give you the same heat work as a cone 5 firing and cone 5 will go down. This is done in industry where a long soak is required. To refire a platter would be difficult unless you slowly bring it up to say 1800 F deg and then continue with a glaze firing. Any soak over 10 minutes is going to start on a path to overfiring. David
  2. Yes push the stop button David
  3. In most kilns a top shelf over everything helps. If you want to use a longer soak try firing to cone 4 and hold 45 minutes. But have a self standing witness cone where you can see it during the firing, so you can stop the firing if it is too long a soak. This certainly will tell you if a longer and slower firing is needed. David
  4. The peep being open could be a problem. Some more questions, is there a top shelf over the pieces? Is the kiln stacked so that there are at least 2 element between shelves? I would say the firing is too fast and another way to get a slower firing than the slow glass is to fire at cone 4 and hold until 5 goes down. If you might be interested I can give you a hold time that may do this. David
  5. Soak means a hold at top temperature, but anything over 10 minutes is going to change the heat work by a significant amount and the longer a soak will eventually get you into a cone 6 firing. You need to be using witness cones to keep track of what is going on. This is why I would write my own program, because your last segment was at 120 deg /hour. Unless your kiln has new elements it probably can't go at 120 deg per hour. The computer controller recalculates the firing based on how fast your kiln can fire within certain limits. My last segment in my user program is anywhere from 30 to 80 deg per hour. This then means you have to make changes to the top temp because you are firing slower and can get the same heat work. It sounds complicated but isn't. Are you using a commercial glaze? If you need more information about making a user program than contact me directly. David
  6. Thank you Marcia, for the explanation. I changed it to 100% and than rounded the results to one decimal point and came up with 99.9% which hardly made any change to the original formula. Next step is for me to try it on my clay. David
  7. Out of curiosity is there some reason for Marcia's glaze not normalized to 100% David
  8. I think you only leave the top peep hole open for bisque firings. David
  9. for a consistency of 70. 1 pound water to 1.42 pound of pottery plaster or (70 parts water to 100 parts plaster ) could use 70 grams of water to 100 grams of plaster David
  10. Take a look at www.matrix2000.co.nz which is an on line glaze course. David
  11. Ramp is either time to get from one temperature to another or set as degrees per hour. You mentioned holding for 30 minutes at top temperature, this would mean you probably fired hotter than Cone 04. Most bisque is at cone 06. If you fire sculpture or heavy pieces slow bisque is okay otherwise I would use fast bisque and save 3 hours total time. The Orton 3000 is a great controller and you should look into making your own programs David.
  12. All the answers to this are good, One comment is that the kiln sitter was meant as a safety device for manual kilns. Somewhere along the line people started to use them to shut off the kiln without using witness cones, which also could cause overfiring problems. So on manual kilns a witness cone is what you should use to determine when to shut off a kiln. Small cones were made for the kiln sitter. Most kilns now use a programmer but again witness cones should be in the kiln.to be sure the temperature and heat work were reached. A 10 min hold for cone 5 will amount to about 14 deg F increase in heat work if the ramp was 108 deg F for at least the last 90 min of firing. David
  13. Matte glazes generally don't fall within limits. That was a big lesson for me in 2014. Limit formulas are mostly for glossy glazes for functional ware. You are correct. Michael Bailey in "Glazes cone 6" states that alumina matte glazes are temperature sensitive and plus minus 50 deg F can make them matt or shiny. So maybe if the witness cones are not the self standing type there could be a temperature difference that regular cones wouldn't show? David
  14. For a cone 6 glaze the recipe you gave doesn't have enough silica to be within the limits, the glaze doesn't add up to 100% and the fluxing power is very high so it could easily be glossy, the COE is also high which will cause problems on some clay bodies. That is why a Currie 35 grid test is helpfull, and probably will show several good glazes. David
  15. One method that might work but is a lot of work is to make a 35 tile Currie grid and fire the tests in one of your regular firings. David
  16. The Fire Right has been around for quite sometime and should work fine. What specific questions do you have? David
  17. The Craft and Art of Clay by Susan Peterson is very good, and has some great information about firing kilns. Since you have a programable kiln you should think about writing your own program. Look at the Skutt manual about the slow and fast bisque and glaze firings, you may decide that the faster firings will work very well, especially after reading about firing kilns. You might even want to try single firing which eliminates the bisque firing. David
  18. Hi Meg If you are having trouble controlling the heat, some questions need to be addressed first. 1. was this kiln meant for natural gas or was it shipped to be used with propane? If there is a nameplate on the kiln it should tell you and also state what the max pressure should be in inches of water column.2. If using propane there should be a regulator on the propane tank set for inches of water column.3. Were the burner cleaned before firing? David
  19. I usually add 1% epsom salts to the glaze. After a month or so it will start to settle but not rock hard, because of the clay content.
  20. have had experience with various types of gas kilns and may be able to help. I live in Reno NV. contact is hdwoodin@gmail.com
  21. Your liner maybe too high in C.O.E. You could try this one. Ferro 3134 15.7 Custer 17.5 EPK 18.9 Talc 9.2 Whiting 14.6 Silica 24.1 total 100 ziropax 5 Epsom salts 1
  22. Where is this kiln located? I am in the Reno NV area and did a lot of work on kilns while on the east coast area around Washington DC. David
  23. Bigceramicstore.com is especially helpful to potters in Northern Nevada. www.Euclids.com is excellent .David
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