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R Fraser

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Everything posted by R Fraser

  1. I was lucky enough to come by nearly 700 used IFB wedges this fall at a Raku workshop in Southern Wisconsin that were in great shape and in January finished a 22 cuft propane fired kiln that has me pretty excited! I fired my first load last week over 7 hours to cone 10 and feel pretty happy over all with the process and outcome. Over the previous couple of years I read 3 different books and oodles of posts and articles on kiln bulding including Nils Lou and Olson's classic before taking the project on. I spent several weeks agonizing over design and layout concerns but in the end going out into the cold and setting down bricks was the thing that finally allowed me to overcome fear and inertia. The fear of buring my shop down was a motivator to be meticulous as well... I have learned a tonne in the process and may tear it down and build it again this summer! Probably not though... Fortunately the wedges were all pretty much all the same with a minimal slope that made prefect little wall bricks when paired with matching wedges, and it gives the brick lines of the wall a wavey wonkey look I am very fond of. After 3 rows of these I spent more time trying to match the ends to make the "waves" consistent. When I had finalized the chamber dimensions (mostly) and the design I spoke with Mr Ward at Ward Burners (invaluable resource) and checked my math on BTU/Hr input and am using 2 MR 100 burners with Baso safety and high pressure pilot and fired at 4.5 psi peak to hit cone 10. My chimney is 6 feet of brick going into Class A double wall stainless chimney pipe. The opening of the roof the pipe passes through is lined with 2inch 2300 degree cerablanket. I had cut it for the exit flue I was using when I had a fling with an old 10cuft Torchbearer updraft gas kiln. I did check the melting temp of stainless steel the morning of the first firing to be safe since the Class A pipe is rated only to 2000 degrees. I tried to make the base of the chimney have some thermal mass to take some energy out of the exhaust, but I suspect at peak temp for a cone 10 firing I am exceeding the rated temp by some couple of hundred degrees. So Anyway, I made a light saber, now am I a Jedi?
  2. 14 inch Egg shaped Raku vessel

    Red-Bronze Raku Glaze
  3. I thought is was like toilets flushing and tropical storm rotation, it depends on your location relative to the equator? Richard
  4. Building a cone 10 outdoor Gas/Salt Kiln

    I too found finches book helpfull. The price on Amazon has got to be an error because that is where I bought mine and it was well less that 700 USD! Amazon was kind enough to offer to buy my used copy for 2.03 USD though! Talk about depreciation. Richard
  5. The Sandia Forge reported up to 30% improved efficiency if I remember corectly. Nils Lou suggested significantly increased efficiency with his recuperating power burner set up but I do not remember if he made any specific claims. I would be concerned that depending on the location of the recuperators and the temp of the exhaust gases a closed loop system relying on natural draft flow to feed the burners primary air the CFM flow of primary air may be low, possibly too low to offer any meaningfull cooling of the recuperators and thus the burner. This would also limit your ability to control the kiln atmosphere to regulating the secondary air flow. The more I think on it the more it seems that to use a recuperating design safely and effectively you are almost obligated to use a blower fed burner system. Nils Lou's book "The Art of Firing" has a nice schematic outlining how to set up a recuperating kiln burner using a power burner system along with a ton of other great kiln construction info, probably the greatest information density per dollar of any kiln building books I bought second only to Olson's Kiln book. The plans and breif outline on design are at the end in an appendix if memory serves.. This is a link to the ABANA web site with the forge plans: ABANA Forge plans Note that this is a very small volume chamber with very short primary air supply tubes to the atmospheric burners in more or less a closed loop design. Richard
  6. This sounds like a recuperating (spelling?) type furnace I first read about when making my first blacksmith forge, I found the plans on the Sandia website (many years ago). It called for oval stainless steel pipe(s) running through the exhaust vent that was then collected and used to supply combustion air to the burner(s). These were atmospheric burners, and it was a small furnace < 2 cubic feet. In Nils Lou's book "The Art of Firing" he talks about a similar design for a ceramic kiln, but it is using a power burner with the blower first running through a pipe matrix in the exit flue to pick up heat before feeding the burner itself. I would say that everything from the flue to the burner would have to be stainless steel. I do not think this would be easily to make safe or simple using atmospheric burners. Richard
  7. Building a cone 10 outdoor Gas/Salt Kiln

    I just built a kiln of this size and to fire to cone 10 in 8 hours (roughly) it needs 320,000 BTU/Hr input, and I have 2 burners that are fueled by high pressure propane that will put out 150,000 BTU/Hr on 3.5 PSI. I have fired several times now and have to throttle back to make it to 8 hours. The design is mostly a modified Oregon Flat top design as discussed in Nils Lou book the art of firing. The Burner you have pictured looks like a MR 750 or MR 100 style burner, but as pointed out type of fuel and how supplied, your elevation, orifice size, size of supply pipe, regulator capcity all influence final burner output. Marc Ward is a super resource on burner questions. Here is a link to the thread I started when I finished my kiln; My First Kiln Build Good luck! Richard
  8. My Laguna Pacifica wheel actually came with the advice to spray the belt with a silcone based spray on lube periodically to keep it quiet. Seemed like it would make it more prone to slippage, but I never did have that problem. When the belt got noisy, like neoprene rubbing unhappily together a quick squirt made it retunr to silent running status. Richard
  9. I bought a ball mill from an EBay vendor that is very servicable for about 150.00. I have milled several rounds of glaze for Raku and cone 10 reduction using the "jars" made from schedule 40 PVC plumbing fixtures (6" pipe, closed end cap, reducer and rubber cap secured with a SS band clamp. I bought ceramic ball media from a ceramic supply vendor in 1 inch, .75 inch and 0.5 inch sizes. It seems to work great, and I have made my own jars since for far less than the EBay vendor was charging. I imagine over time some of the PVC winds up abrading off the inner walls, but I have assumed any present in the glaze slurry burns out early in the firing and have not seen any ill effects in fired ware. Richard
  10. I read a tip somewhere that you can use the same diffuser to mass produce bits of wadding from your favorite wadding formula, just roll it into the diffuser, let it dry a bit and invert. Presto! Never occured to me to make little itty bitty tiles. Could make a very cool mosaic with these! Richard
  11. Throwing in gloves

    I have a safety tip. Much of what is sold as "consumer grade" disposable gloves are not latex free, and you may have to read the fine print to know it. All health care facilities are now "Latex Free Zones" due to the risk of serious allergy developing over time to latex both in staff and patients. Significant allergy can occur often only after sustained chronic exposure. The non-latex gloves do not have the same degree of elasticity and in some cases the same feel as the latex based gloves. Make sure you look for latex free on the box, particularly if you know or suspect you have a latex sensitivty. When I work with seriously toxic stuff (ferric chloride,soluble lithium or barium salts) I have a set of reusable gloves made for use with toxic and or harsh chemicals that go almost to mid forearm. I rinse, dry and repeat over and over again. I do keep some nitrile purple gloves similar to what prehosptial personell use for barium or lithium containing glazes as they are much more robust and can be dried and re-used for a bit. I also collect shower caps from every hotel that puts them out to cover my banding wheel when spraying or sloppy glazing. The glaze pops off when dry. Richard
  12. I have a strong affinity for a Shinto style belief system when it comes to my kilns, and generally offer premium Sake or good quality single malt Scotch to my little kiln Kami cups. I also feel strongly that my kiln Kami do not like to drink alone, so after loading and before lighting the pilot burners I have a toast or 2 to the happiness of the kiln and its ware, and another wee dram to wish for a safe & happy firing. It is surprising that the Greeks felt they needed more antagonistic dieties than charitable ones when it came to their pottery. Richard
  13. I love mine, and the free wheel feature is actually pretty cool. I have not noted bogging when throwing larger bits of clay though I must admit I do not often ask the wheel to spin more than 30 pounds. It is very quiet. I like it much more than the Pacifica 400 I was using. I threw on Brents in a studio and prefer my Shimpo. Richard
  14. My first real kiln build

    Thanks for this. I was pretty sure that the math was done for this. This info is very helpfull. Richard
  15. Bone Head Mistakes

    After enough electrical disasters (sawzall vs. 220 line on the far side of the joist, small electrical fire after 220 wire of new dryer- fire department not involved) to make most sensible people actually pay a qualified person to do the work you would think I would know better, and yet… I bought a new 10 CF electric kiln and put in an 80 amp breaker for the 220V service, and bought some copper cable the size of a baby’s arm to hard wire the kiln to the junction box. Now I know the conventions for electrical wiring i.e. green = ground, and the large green cable in the guts of the kiln clearly was firmly mounted to the case & stainless jacket, so of course it is the ground right? The 8 gauge cable had 4 colors in it, black white, green, and another one (red). So of course this would be easy. I went over it all twice before energizing the panel and the breaker, and the kiln panel made a test tone like all was Okeedokee. So, following the testing instructions I was going to check that all the elements operated correctly and set up the kiln vent and plugged it in. When I energized the kiln there was an impressive flash and rather acrid smoke followed immediately by a warm wet feeling in my pants. I turned off the kiln breaker and went to see WTF was going on. The Kiln vent seemed to stop working and on closed investigation I noted the ground wire of the kiln vent had magically disappeared after melting its way through the plastic insulation. There was no other damage anywhere on or about the kiln so perhaps it was faulty wiring in the kiln vent, and yet it worked fine until I powered the kiln breaker. So I thought I should check the set up and took the wall and breaker box apart. Turns out somehow the green cable was attached to not the ground but to one of the energized legs of the panel, so my kiln jacket was energized with ½ of the 220 voltage, the black cable to the other and the white (should have gone to the energized pole) to the ground/neutral. The flash was indeed the ground of the kiln vent vaporizing because of its proximity to the rather “amped up†kiln jacket and a whole bunch of eager electrons with no place to go. Now, I appreciate the fact that these electrons did not pick me for the best exit to ground, and that after such a terrifying experience I should have paid the electrician to fix my problems. For a whole day I considered giving everything to do with electricity away but a lack of common sense and mortality prevailed. I corrected the faulty wiring, checked it a second and third time, replaced the kiln vent cable with a new grounded plug (one that still had a green wire) and standing a more than safe distance used a broom stick to energize the breaker to the kiln. Everything worked perfectly, all 3 thermocouples worked fine, all solenoids functioned and all kiln elements lit up. I am happy to say the kiln has been firing flawlessly since. My wife has been spared the gory (or nearly gory) details on this.
  16. My first real kiln build

    Wow, that is a very cool set up. I think instead of re-building this kiln this summer perhaps I will build some power burners. I do have a couple of questions: are you running natural gas or propane, if propane are you on 11in WC or high pressure. How did you determine the CuFt/minute for the blower to orifice match? Do you have an orifice chart? To do this my current build the high pressure pilots and Baso's were by far the most expensive part, but safety first. So I would need to base any power burner on the high pressure propane source if I want to include the pilots and Basos. I do have the Baso valve left over from the original burner ring from the Torchbearer and it is set up for 11in WC propane, and I know it still works, but it would be awkward to plumb it for 2 burners. I discussed the merits of high vs. low pressure with Mr. Ward previously and the choice really only mandates the orifice diameter and may affect the turn down ratio in the end. But for the best efficiency getting the orifice right is probably pretty important. Do you have a parts list for that build? What kind of flame retention nozzle is that? I like the inline design with the blower passing straight through. Did you say the orifice is directed away from the blower, as in following the airflow? Sorry to bomb you with questions…
  17. Raku firing process

    I asked Marc Ward about this when I was planning my Raku kiln and he felt positioning the burner in the middle aimed straight in was fine, as the high pressure burner generates alot of turbulance on its own. I was going to try to point it along a tangent to the kiln interior to swirl and mix it up inside but it would have been difficult to get it aimed that way, and the flame tends to hug the wall it is aimed along anyway. Straight in has worked great for me and if there are any "cool spots" in my kiln I have not been able to find them. My octagonal shelf sits on three 8 inch posts which puts the shelf about level with the surface of the brick and the flame path is straight between the silts. Richard
  18. I need some advice about platter related matters. I recently threw 10 platters that started with 3kg to 4 kg of stoneware (Continetal Clay Buff Stone Ware with Ochre), and 2 havecracked in the middle during drying after trimming the foot rings. I had trimmedthem a little wetter than I typically like but had time constraints as usualand felt they were sufficiently firm for trimming. After trimming I put theplatters on ware boards and covered them with plastic sheeting (formerlykitchen garbage bags). For certain the rims were a bit dryer than the center sothere was some moisture disequilibrium, but no more than any other time in thepast. No matter what I do, it seems I lose about 20 to 30% of these plattersabove 15 inches. I am very compulsive about compressing the base as Ithrow. Does anyone have a secret tosuccess with larger platters? Or should I plan for loss and just be happy it’snot half of them (yet).
  19. Large Platter Woes

    Thanks to all that replied to my post. I found the suggestions most helpful. I found the round foam pads I purchased a couple of years ago specifically for the purpose of trimming large platters and started to use them again as well as using a thin plastic recycling bag with the center cut out to the size of one of my 12inch bats to keep the rims from drying. I threw another 8 platters from 9 to 10 pounds resulting in around a 16 inch platter and not one has cracked. I really think that in addition to keeping the drying even, trimming the foot ring with the center of the platter well supported is critical. I am certain the last group of platters were lost because I was trimming them on a thrown clay chuck that did not offer any support to the center, and the rim dried too quickly. At least I got a good look at the middle of the platter to verify that the base and rim was even in thickness
  20. My first real kiln build

    I love your burners! I was going to build power burners as I have a blower from by forge that I am not using but was not sure about the orifice size and pressure, to air flow rate ratios for optimal performance. New power burners are big $$, but as you demonstrate very easy on the wallet in cost of firing. I think I am burning at least 14 gallons of propane in a firing for this kiln. Did you make the burners yourself? You are probably using low pressure propane too? Richard Here is a picture with a list of parts of my forced air burner. If you have any questions let me know. Aloha, Ken Love it! Guess who is going shopping this week end... Thanks, Richard
  21. Raku firing process

    R Fraser, now that's a kiln! Very nice. I think enlarging my inlet and possibly the outlet is probably the answer for my problem. Why would you want to create back pressure? If I want to alter the kiln atmosphere during the firing, ie to fire the glaze to maturity in a reducing atmosphere can alter the glaze appearance, in which case I often let the glaze cool more before placing it in the reduction container. It mainly allows me more options to manipulate the final glaze appearance. Restricting the exit flue alters the flow of secondary air which changes the effeciency of the combustion and can shift it to a more reducing atmosphere. Richard
  22. My first real kiln build

    My first firing was about 10 years ago, no fiber, one forced air burner, cone 10 in 4 hours. It was too fast, unlike the Olympic Torchbearer the top was 2 cones cooler. Over the years I added fiber, another burner and two collars. I added fiber to slow the cooling for better glaze colors. Adding the second burner at the top evens out the firing. The forced air burner are very efficient. I now fire in about 7 hours to cone 10 with about 9 gallons of propane. Aloha, Ken I love your burners! I was going to build power burners as I have a blower from by forge that I am not using but was not sure about the orifice size and pressure, to air flow rate ratios for optimal performance. New power burners are big $$, but as you demonstrate very easy on the wallet in cost of firing. I think I am burning at least 14 gallons of propane in a firing for this kiln. Did you make the burners yourself? You are probably using low pressure propane too? Richard
  23. Raku firing process

    It is true that if the secondary air is restricted by having the burner too close to the inlet port, and or the burner port diameter is too small relative to the burner diameter the temp rise will quickly stall. On my current raku kiln I run my MR 750 around 2 inches out, and the inlet diameter is an inch to an inch and a half greater than the burner diameter. I usually leave the burner damper open fully. The exit flue is 8 inches and when I want to reduce the glaze during firing I can adjust the exit flue with an IFB to create a little back pressure. My kiln is 24 inch diameter cylinder by 26 inches high insulated with 1 inch 2600 Cerawool. I have had it as hot as 2230 degrees F. Don’t ask why. My trash can kiln I used about the same inlet diameter and I think the exit flue was at least 6 inches, again restricted if need be with an IFB. The base was dry stacked 2300 IFB. I never had trouble with stalling as long as it could breathe well.
  24. Raku firing process

    My first raku kiln was a brand new garbage can with 1 inch of 2300 degree cerawool liner held in place with porcelain buttons. I used a 300K BTU high pressure propane weed burner for the first few firings then a MR 750. Like Marcia says about an hour for the first load and 30 to 45 minutes for following loads. It still amazes me that even though I routinely hit 1900 degrees on my pyrometer the paper lable on the can never burned off, only just slightly browning over time. The temp probably could have come up faster but I always try to go gently through 950 to 1100 degrees so I slow down the process, really letting it go fast after 1200 degrees F.
  25. Large Platter Woes

    I should have added that I use a large cut off bow I made to free the platter immediately after throwing. The cracks pretty much cut down the middle, more or less tracing the diameter of the platter. With previous platters I had used 2 inch high density foam bats to support the span of the platter. This time however I threw a large clay chuck to trim the platter and the middle was un-supported. Several - probably all of them that cracked - 6 now, were soft enough I am sure there was some sag, and the dryer ones probably developed the cracks while trimming since the chuck really only supported the outter edge of the flat part of the platter. As an aside I should have searched the forums first before posting. Thanks to the moderators and regulars for not posting the "have you tried the search feature before posting" reply. The links posted as well as the replys were very helpful. I have just thrown 2 more to replace the first losses and I will try to keep the rims from drying too fast. Does using wax resist ever prevent the rims from fully drying and increase the risk of cracks during bisque firing?
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