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Chris D

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  1. Well, the floor (so far) was a success. We reamed out the burner orifaces to #28 for gas (turns out they were propane orifaces) and set everything up and gave it a whirl. Worked pretty well! I think we have the fuel/air mix off a good bit, but we were still able to get the kiln to 1,900 degrees in just a couple of hours. Some photos: The floor, in place, with burner ports cut: Detail of burner head and port: Low flames on the first firing: At full burn, just before we shut it down: After cutting off the gas: The goal is to get the thing to cone 10. We have a long way to go, and I can tell that the 4-500 degrees above 1,900 we need to get are going to be hard-earned. But I think we can do it. There's certainly no shortage of gas...we got it to 1,900 degrees with the valve barely cracked. Soot around the lid in places where there were heat/flame leaks tells me that the mix was probably starved of air, but that's just a guess. Very excited at the success so far, but not sure if we need to increase primary air (with the burner venturi shutters), secondary air (with larger burner ports...we cut them pretty small) or both! Time and experimentation will tell. Looks like the next project for this thing will be to rebuild the lid. After the first firing (probably in a decade) the part of the lid near the hinge was crumbly and falling apart. I can see the whole thing crashing down through the kiln and crushing the floor, so maybe we should replace it sooner rather than later. I really dislike the hinge system that olympic devised for this kiln. Seems built to fail. The lid is pretty heavy, and all that supports it when it's open are a couple of brackets that are attached to thin sheet metal that gets all of it's structural integrity from the K-23 firebrick that it's squeezing. Bad design. Was thinking that it might be good to weld up a frame to go around the kiln and create a "bridge" over the lid with a pulley system so the lid can be lifted with a little winch, kind of like how some raku kilns are designed, but only lifting the lid. Anyone ever see something like that?
  2. Kiln gas type question

    I'm pretty sure (from the reasonably extensive research I've done) that natural gas venturi burners for kilns have #28 orifaces. You can get a #28 drill from your local hardware store. If it fits, it's a natural gas oriface. If it is too small for the #28 drill, it's a propane oriface. We had propane orifaces on our burners and drilled them out for natural gas. Yet to see how that works, but I've read it's no problem.
  3. Got everything mortared up, and strapped the band on it: Scraped off most of the excess mortar and then plan to sand off the rest once the mortar has had time to set/dry. At it's thickest, the mortar is maybe 1/16 inch, and I buttered both sides of each joint before mating the brick surfaces. Everything seemed to stick pretty well together, though with such thin joints, it was a challenge to firmly assemble new bricks to the already-built floor. Had to be careful and forceful at the same time. A few notes: I wouldn't try this if I had no previous experience with other sorts of mortar. This is sort of a tricky application, and wouldn't be great for a true beginner. you need to work pretty fast. The mortar sets quickly with contact with air, but takes a good while to set in the center of the joint (we tested this overnight on some scrap) A 28-inch "round" kiln's floor actually has a 34-inch diameter floor. 2 boxes of a dozen K-23 bricks are *just* enough, but you're using scraps from bricks you cut to complete it, so you have to plan very well, or buy a couple of extra bricks. 2 pints of Sairset mortar are *just* enough. We had less just a few tablespoons of mortar left. YMMV. Don't count on the band to "pull everything together" when you're done. The band can be tightened pretty tight, but doesn't come anywhere near tight enough to squeeze the bricks together any tighter than they were when you put them together initially. Really hoping this works. If it does, we'll have saved some good coin. The floor from Olympic was a couple hundred bucks, and was going to be more than $100 to ship because of its weight, size, and fragility. All told, the bricks cost $66, the mortar cost $7, and the band from Olympic was $30. $100 for a new floor. Not pretending it'll be as good as one put together by pros, but it should be "good enough!" If it doesn't work, it was only a $100 mistake. I've certainly made worse mistakes! Ha!
  4. Interesting! We have a gauge that measures inches of water to put in between the valve and the burners so we can keep track of the gas going to the burners. Hopefully this will help us figure out too if we have inadequate gas at the kiln. There's quite a bit of 3/4 inch line between the kiln and the street, so we'll have to see.
  5. Well...We did some more research in the meantime, and learned that for Sairbond to actually "set" it needs to be fired to cone 10! At least that's what the folks at Aardvark told us. Of course, they told us we should have just bought a floor from Olympic, but whatever. The guy at Aardvark told us we should have gotten Sairset, which is a pre-mixed mortar that air-sets. I spoke with people at Harbison Walker, too, and they sent me some information about using both products (pretty useless) and told me that Sairset has good strength after air-setting, but really gets it's full strength after it reaches a temperature around 850 degrees F. That sounds a lot easier to achieve. Without another kiln that can accommodate this 34-inch diameter floor, there's little chance of us heating it to cone 10...ever, probably! Ha! We pre-cut two boxes of K-23 IFB for the floor, went back to Aardvark and got a few pints of Sairset and are ready to put the pre-cut pieces of the floor together: On my way out to the studio to do that now... Will report back on success/failure. I'm with you on the whole "added support" for the floor. The Olympic-supplied metal stand is a flimsy, sad affair that I really can't believe was sold with the kiln originally, but looking around, I see that I probably was. I'm amazed at how incredibly soft the K-23 bricks are. That this floor could support a loaded kiln is an amazing concept to me. I can crush these things with my hands! Short-term, I plan to bolster the floor with some spare square-steel tubing I have laying around. Long term, I plan to fab up a support structure similar to what Peter at Summit Kilns uses for his GV-27 burner system. That guy knows what he's doing! Chris
  6. Thanks Mark. All good advice (especially calling Aardvark. Not sure why I didn't think of that!). We planned to dry-fit everything then mortar it together, cook the heck out of it, then cut the floor to shape. Thinking about it again, it'd probably be better to cut the bricks before mortaring. That way the band can hold the whole mess together while it cooks. Spraying the blocks with a bit of water sounds better than soaking, too. Chris
  7. We got a new floor band from Olympic, a couple dozen K-23 bricks from Laguna Clay, then swung by Aardvark for some supplies, including a bag of Sairbond heat-set mortar. This is the stuff that was universally recommended for putting the kiln floor together. Now that it's time to actually assemble, cut, and drill the floor, I'll be damned if I can find the first scrap of information online about how to use this Sairbond! Ha! We're going to build the kiln floor on a well-braced 4'X4' piece of extruded steel so it doesn't have to be moved between assembly and heat-setting (plan to just slide the burners under it and heat the whole thing at once, and evenly). It seems before we start into this, we should know: How do you mix the Sairbond? What prep work needs to be done on the bricks before mortaring? Do they need to be soaked in water so they don't draw moisture from the mortar? What temperature do you need to get the mortar to to make it set? Does the mortar have any "green" strength at all? I'm amazed at the dearth of information on the internet about this. Even the mortar manufacturer's website doesn't have anything more than the MSDS for Sairbond. Great. Anyone have any experience using this stuff or general guidance to offer? I have some pretty good guesses about what we should do, but would welcome any advice from someone who's been there. I'll post some photos if we have any success!
  8. Nice. Thanks again. This is what I was hoping to hear, and what you say about the sitter makes sense (and explains the destroyed state of the kiln end of the sitter we have). Firing in reduction was the main reason a gas kiln was acquired instead of electric, so we'll be leaving the sitter out of the final equation. I need to do some homework, but I hope you don't mind if come back fishing for specifics on your burner control system eventually. We're pretty much "babes in the woods" on this front.
  9. John, Thanks much for this heads-up. I've learned not to talk too much about skirting codes in forums, since it tends to get people heated up. No pun intended. That said, the propane option is one we hadn't really thought of. This would add an element of portability, too. Makes me wonder where it's okay to install the "stock" kilns that don't even have pilots and have to be lit with fire sticks! Ha!
  10. Hey Neil, Thanks for the feedback. Solid gold. The previous owner had the kiln on natural gas, so I assume that they're the proper jets for the setup we're putting together. That said, do you know off-hand if BTUs can be estimated based on the diameter of the jet orifice? That would probably be too simple... I'm curious about sitters not being for gas kilns...is that because of the convective heat of an open flame, as opposed to the radiant heat of an electric kiln? Not sure if I have the right words there, but my idea is that the gas heat is much more intense around the outside of the kiln from the very start...so a reading from the spot where the sitter's cone is would be much higher than the rest of the kiln? I'm not the ceramicist on the team, so many of these concepts are new to me. I wonder why the original owner outfitted the kiln with a sitter if they're not for gas kilns? Hmm... Thanks for the tip on the high-temp shutoff. I was also thinking about replacing our old pyrometer with a homebrewed system of parts from these guys...maybe even multiple sensors at different locations in the kiln? Thanks again!
  11. Thanks Mark. That's what I was thinking. Perhaps more even, but maybe overkill. I'm figuring on the floor being pretty simple, and thanks for pointing out the merits of locating the burners near the outside. My plan was actually to just extrapolate the measurements from photos of other kiln floors.
  12. Thanks Marcia, Do you say that because home gas line pressure is generally low? The people at Olympic told us that you don't need a pressure regulator on a home gas line since it's already generally at the correct pressure for the kiln. Perhaps it's a volume issue?
  13. Hi folks, Brand new to the site and forum, which looked like the best place for a question like this. We are working on rebuilding an Olympic Torchbearer gas kiln that was purchased a couple of years ago in non-working condition. It's much like Olympic's current 28-inch offering, the Model 2831 G. One key item the kiln lacks is a floor. It fell out in pieces when the kiln was purchased. We've done enough homework to know what sort of brick, mortar, and techniques are required to remanufacture the kiln floor and have ordered an appropriate stainless steel floor/lid band from Olympic. The kiln came with a six-burner setup that looks like it is probably not even original to this kiln: You can see that there would be no way to position the holes in the kiln floor for the burners so that the burners weren't right at the edge of the floor. Olympic doesn't make any six-burner torchbearers anymore. We're planning to just cap two of the burners and reposition the remaining four to be closer to the center of the floor, more like this; ...only with four instead of two burners, of course. My first question is this: Would there be any advantage to maintaining the six-burner setup? I don't know enough about it to have an opinion, but once we decide on a certain number of burners, we're kind of stuck with that configuration after we cut the holes in the floor, and I would like to get it right the first time. We have a pyrometer that works (needs to be calibrated) and a Model K Kiln Sitter that needs some parts but should function just fine after minor repairs. The valves and gauges on the gas line are in pretty dubious condition and will have to be replaced. The kiln will eventually be connected to a home natural gas line. We've seen a dizzying array of valves, electronic wall-mounted controllers, and thermocouple devices that one can add between the cutoff gas cock on the kiln and the house line to regulate the gas flow to the kiln. Building codes will dictate part of what we include, but I'd like to hear people's opinions on what a minimal setup would include between the house line and the kiln. We're not looking to automate any processes that we don't need to. Thanks in advance for your help! Chris