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David Woodin

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Everything posted by David Woodin

  1. I automated my gas kiln which is a Bailey studio down draft 24 cuft and has two burners. I used a modulating gas valve on the main gas line feeding both burners. The valve is set so that it doesn't shut off tightly, so the standing pilot is always on, I also limited how far open it will go so a good air gas ratio is always maintained. The auto part of the firing is only used up to body reduction when the kiln is then put on manual and the rest of the firing is done on manual. David This is what I was wanting to achieve by using multiple two way on-off solenoids in parallel. Once at reduction temp range the air flow and damper would all be manually controlled. Do you remember the valve manufacturer and serial #? Jed The valve is a Maxon butterfly valve, CV-BV series. The actuator is a Belimo AF-24-SR and the controller is an industrial 4 to 20 MA output controller with a programable ramp rate, Auto/ manual control, type K thermocouple. It is possible to find controllers as a surplus or used item. David
  2. I automated my gas kiln which is a Bailey studio down draft 24 cuft and has two burners. I used a modulating gas valve on the main gas line feeding both burners. The valve is set so that it doesn't shut off tightly, so the standing pilot is always on, and so is the burner. I also limited how far open it will go so a good air gas ratio is always maintained. The auto part of the firing is only used up to body reduction when the kiln is then put on manual and the rest of the firing is done on manual. David
  3. I have done jiggering for years and never had the problem shown in your pictures. I use Laguna WC370 Amador clay which I also use for throwing. My first thought to your problem is the molds themselves. Even when I leave my clay on the molds too long they just float off the mold, no warping, no cracking. Was the plaster fresh and mixed to a ratio of 68 to 70? I noticed that some of the mixtures for pure and simple don't use this consistency. Perhaps pictures of your mold surface would help. My thesis was on Jiggering and done in May 2003. David
  4. You should change the elements and broken holders otherwise the new elements are going to sag. Pining them defeats the purpose of having element holders in the first place. L & L has plenty of information available on line to help you. To get the bricks out you will have to loosen the kiln jacket. David
  5. I have seen element holders broken and some time missing on older L&L kilns the elements than sag and are hard to get out to replace. I would think the only thing to do is to replace the holders, but this may mean getting the brick out to slip in the holder? David
  6. The food safe limits show .15 to .35, Matrix shows 0 to .3850, Insight shows .3 to .5. If you want food safe I would stick to the food safe limits. Other wise test it for your use. David
  7. Sometimes the plastic top that the gauge screws into warps, and needs to be replaced. David .
  8. Try using a Pelican Stealhlite 2400 flashlight cost about $ 24.69, you should be able to see cones with this bright light. David
  9. I am not sure you can use the COE of the clay as the guideline for crazing. I use a Laguna clay with a COE of 4.64 and have no crazing problems. Jim Robison wrote an article about Clay in Studio Potter volume 9 number 2 June 1981. I had the good fortune to attend one of his workshops where He gave out 9 recipe's so you can test clays to see what COE of glazes will work on a clay body. He tested from COE 5.29 to 8.11. I line blend from COE 5.05 to 8.33 on every clay body that I am thinking about using. David
  10. The 12 hour soak may have brought you to cone 07, which may not of hurt anything. If the controller has a review button press it and you will see what the program is. You can change the program to what you want and if the kiln is still hot the program will take off from that point. So you don't have to wait for the kiln to cool down. I may not be correct about this so watch the kiln to see if that is really happening. It is always a good idea to press the review button to see if the program is as you wanted it. David
  11. I use a controller on my kiln but never shut the gas completely off. This may be impossible to do on your kiln but if you can control it manually without starting and stopping a burner than it can also be done automatically and will follow a traveling setpoint. David
  12. You could try some light blues, .3 Cobalt Carb, varying % of Rutile. Rutile by itself sometimes produces great colors try line blend up to 12% . Lovely pots. David
  13. There is a great on line glaze course. Look for Matrix on line glaze course. David
  14. There is a great on line course for glazes. Look up Matrix on line glaze course. David
  15. An hour soak at a ramp of 108 deg F will bring down cone 6.(2230 F) A 17 min soak will bring down cone 5 1/2 (2201F) . So it would be better to try what Neil said and start off at 10 min soak at cone 5 ( 2176 F), which would be about 14 deg F higher than cone 5 down+14= (2201F). David
  16. I can see why you would want to change the grid, because the Currie grid produces a lot of tiles way out of any limits. Another way to get more meanfull results is to pick a limit that is at the cone you are interested in. For example Matrix at cone 6, than A= AL .56, Si 1.9 B= AL .56 Si 4.2, C= AL .21 SI 1.9, D= AL.21 Si 4.2 or Matrix at cone 10 A=AL .7 Si 2.63, B=AL .7 Si 5, C=AL.27 Si 2.63 D= AL.27 Si 5. David
  17. Your grid is 5x5, Currie grid is 5x7 is that your intent? Have you compensated for this? David
  18. I am not sure what limits you are using, but at cone 6 it barely fits Matrix and Green & Cooper. At cone 9 Insight, at cone 10 Insight, Food safe, Matrix, Green& Cooper, Cushing Glossy Clear. Since you probably want cone 6 I would suggest changing your Alumina Silica ratio to get into the cone 6 limits for Insight or better yet food safe limits. This could help the bubbles problem. David
  19. How thick do you apply the glaze, any binders or suspension materials? The clay fires from cone 5.5 to 9. you are firing at the low end. Fill one of your test pieces with water and place it on a napkin look at it the next day, it may leak at the temperature you fire to. It has a high water absorption even at cone 9. Does any glaze fit properly? David Hello David, I will test that! Since I'm really new to pottery, how do I generally find out the ideal firing range for clay body? They only inform about the max temperature in the shop... Hi Martin, The clay I use says cone 10, I fire to cone 9 down with cone ten starting in a gas kiln. I use the same clay for electric kiln firing and fire it at cone 7 and the clay doesn't leak water at cone 7 but will leak at cone 5 and 6. This will not help solve the blistering problem you now have which could be caused by the bisque firing program, not taking enough time between 1000 deg F and 1200 deg F, which will help burn out all the organic material. David
  20. The very best option is self standing cones, but they are about twice the price of regular cones, the next best is to get the cone plaques to set the cones in. You can get very good results by making your own cone plaques. 1. the base of the cone is cut so you will get the needed 8 deg angle. 2. when cones are set to fall to the left then the numbers will show. 3. Height above the clay is 2" for large cones when reading the large cone chart, or 1 3/4' for the self supporting cones chart. There is a 2" mark on the cone, it is the horizontal line of the Orton symbol. The 1 3/4" line is the top of the Orton symbol if you want to read the self supporting chart. 4. Make a clay pad about 5/8" thick by 1" wide by 3" long. 5. Mark a straight line lightly on top of the pad, push a cone in to the clay up to the 2 " or 1 3/4 inch mark, the number will face you at an angle to the line, and the flat surface is on the line. The bending surface is not on the line. Then push in the next cones to the same depth following this line etc. The cones will fall and miss each other if you do this. The previous posts with picture will then make sense. Too bad that Orton changed their style of box and left off or didn't have the room to print the facts you needed to set cones properly. Remember that cones go from 022 to 0, then 1 to 14. This means for a cone 05 firing you use 06, 05, 04 starting from the left of the cone pack. David
  21. It looks like the cones are also set into the clay at different depths David
  22. How thick do you apply the glaze, any binders or suspension materials? The clay fires from cone 5.5 to 9. you are firing at the low end. Fill one of your test pieces with water and place it on a napkin look at it the next day, it may leak at the temperature you fire to. It has a high water absorption even at cone 9. Does any glaze fit properly? David
  23. If you skipped step1, this meant the kiln went as fast as it can to step 2. That would not be a good idea as the kiln could have been going at 500 deg per hour or more and anything could have happened to the glaze as it tried to adhere to the pot. I am wrong as to what I said about this glaze. It does have a lot of flux and doesn't fit in cone 6 limits. I fired it using EPK instead of OM4 ball clay to cone 06, it was a very dry white surface no blemishes, than fired to cone 4 still a dry white surface, then to cone 6 still white but not quite as dry a surface, cone 8 still dry off white matte. Please post the firing schedule used. David Hello David, the 1st step in our schedule is identical with the second one in the linked schedule, so we start from 0 and go with 166°C/hr to 945... Do you think that's too fast then? I'm sure it won't take too much more energy if we drop it slower, but again, it's a wild guess for me in terms of how much to drop it. Thank you! M Hi Martin I tried firing the glaze at your temperature rate and there was no problem except that cone 6 was started but not down and probably it needed a 23 minute soak. The glaze is a dry white and not a good glaze. I also wonder if maybe one or more ingrediants was contaminated, this can happen in an open studio, it has happened to me in the past. Hope you have a chance to try the glaze I sent you. David
  24. If you skipped step1, this meant the kiln went as fast as it can to step 2. That would not be a good idea as the kiln could have been going at 500 deg per hour or more and anything could have happened to the glaze as it tried to adhere to the pot. I am wrong as to what I said about this glaze. It does have a lot of flux and doesn't fit in cone 6 limits. I fired it using EPK instead of OM4 ball clay to cone 06, it was a very dry white surface no blemishes, than fired to cone 4 still a dry white surface, then to cone 6 still white but not quite as dry a surface, cone 8 still dry off white matte. Please post the firing schedule used. David Hello David, the 1st step in our schedule is identical with the second one in the linked schedule, so we start from 0 and go with 166°C/hr to 945... Do you think that's too fast then? I'm sure it won't take too much more energy if we drop it slower, but again, it's a wild guess for me in terms of how much to drop it. Thank you! M Thanks for the information. I don't think that is the problem although most people want to make sure all the water is out of the glaze, therefore the first segment is used. I never could get this glaze to become a good surface even firing to Cone 8, too dry. I am afraid it is your clay. To be sure try a small like 100 gram batch of the glaze I gave you if you have the materials, make sure it is dry before firing that fast. If you don't have the frit tell me what frit you use and maybe I can redo the glaze for you.
  25. If you skipped step1, this meant the kiln went as fast as it can to step 2. That would not be a good idea as the kiln could have been going at 500 deg per hour or more and anything could have happened to the glaze as it tried to adhere to the pot. I am wrong as to what I said about this glaze. It does have a lot of flux and doesn't fit in cone 6 limits. I fired it using EPK instead of OM4 ball clay to cone 06, it was a very dry white surface no blemishes, than fired to cone 4 still a dry white surface, then to cone 6 still white but not quite as dry a surface, cone 8 still dry off white matte. Please post the firing schedule used. David
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