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Hello All,

I am very new to ceramics, but I am keen to learn as much as I can.  I recently acquired a gas kiln in as-is condition, and I need to know what to do to make it safe to use. It is completely manual and has no modern safety or control features.

It is a Cerami Craft kiln of late 60's to early 70's vintage.  All I have been able to find online for this particular kiln are a couple of ads from old trade magazines from '72.  It also came with a booklet that is more of a guide for use than actual instructions.

  • 7 cu ft
  • 5 burners underneath
  • Natural gas
  • 2 peep holes
  • Manual damper on top
  • 1 WC gauge
  • Retrofitted "Pilot ring" which looks a bit sketchy to me
  • Manual Orton Pyrometer

It came with shelves, furniture, and several boxes of various pyrometric cones. I was told the last time it fired was spring of '17. It was a single owner kiln and used 3 -4 times / year since it was new, according to the previous owner. The burners are interesting, and very basic in design: essentially a split steel cup venturi that holds a ceramic cylinder.

Before I fire this antique up, I want to make sure I have a functional and safe tool.   (BTW - I am aware the liner between the sheet metal and bricks is asbestos). Total $ invested so far in this project has been the cost of moving it from its previous home of ~50 years to my backyard, so I have a bit in the budget to upgrade. I definitely would like to do some upgrades for convenience and safety, so all suggestions are welcome. I am also not sure whether I need a permit to run a kiln in my city.  The codes on their website are not very specific.

Please refer to attached photos for an idea of what it looks like. I could only attach 2 in this post.

OK experts, fire away!

IMG_0113.jpg

IMG_0110.jpg

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Hi Mark,

I will attach more photos to answer your questions. It is pivot-hinged at one side and swivels open.

Not worried about the asbestos. I mentioned it because of its age, and in anticipation of remarks from others. I don't plan on disturbing the liner unless absolutely necessary, and I would take all needed precautions.IMG_0091.jpg.7ec88199c3e827ef95fdaaed61975417.jpg

 

IMG_0092.jpg

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As to whether or not you need a permit, you'll have to ask your city. It's different for every one. Is that copper line a pilot ring? I agree, it looks sketchy, and doesn't really provide any safety unless there's also a pilot valve on the gas line and a thermocouple to sense the flame on the pilot ring. I can't tell from the photo if there's a safety valve or not. Personally, I'm not a big fan of pilot rings as a safety system. The holes in the ring could be plugged up at any of the burners, but as long as it's not plugged where the thermocouple sits it'll keep the gas running. Unfortunately, putting a pilot valve and thermocouple on each burner isn't really possible, so we have to live with the ring. Just check it each time you light up the kiln to make sure the flame is working at each burner. As long as the burners aren't falling apart from corrosion, it's worth lighting it up and seeing if everything works. Is it set up to run on propane or natural gas?

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Thanks Neil.

It is set up for natural gas. The pilot ring is 1/4" perforated copper.  There are tiny holes all around it; not just at the burner.  The previous owner says she never left it unattended while firing, but had someone install the pilot ring as a precaution anyway.  Not exactly safe, but better than nothing? There is no safety valve or pilot valve w/thermocouple. I'm thinking of installing a new ring with thermocouple, and reducing the number of pilot holes to 2, each pair pointing at a burner.  Theoretically that should mitigate clogging problems.  

The piping appears to be 3/4" galvanized.  I've been doing some research to find out what model Baso safety valve, pilot valve and thermocouple (or combination thereof) would be appropriate for my application, but I have not found anything yet (kinda hoping to find answers here).  

Would you happen to know what clearance (roughly) I need to keep around the kiln while firing? It is on the side of my home near a stucco wall and there is no roof eve (20 ft above) to worry about.

Here's a photo of the inlet valving.  It is functional, but does not instill a warm fuzzy feeling.5a54117f9ef0d_IMG_01122.jpg.dae99250208417de568128747bcfc056.jpg

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Interesting stuff. It looks like that's 3/4" pipe? If so, you need a Baso H15DA, which is made for use with low pressure gas and has a 1/4" takeoff for the pilot. Ward Burner carries them, but you can get them all over the internet, and there are other brands available, too. Baso is just the standard that everyone uses. I've seen them on Amazon, too.

It probably wouldn't be bad to take apart the whole gas train and rebuild it with new pipe. Pipe is cheap.

Since you'll have flame coming out the top, you'll want to keep it many feet away from the house, the more the better. I don't know that there's a specific number, but personally I would go at least 8 feet away to feel safe. You'll probably need a gas hose to make the connection from the house.

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1 hour ago, neilestrick said:

Interesting stuff. It looks like that's 3/4" pipe? If so, you need a Baso H15DA, which is made for use with low pressure gas and has a 1/4" takeoff for the pilot. Ward Burner carries them, but you can get them all over the internet, and there are other brands available, too. Baso is just the standard that everyone uses. I've seen them on Amazon, too.

It probably wouldn't be bad to take apart the whole gas train and rebuild it with new pipe. Pipe is cheap.

Since you'll have flame coming out the top, you'll want to keep it many feet away from the house, the more the better. I don't know that there's a specific number, but personally I would go at least 8 feet away to feel safe. You'll probably need a gas hose to make the connection from the house.

Yep. 3/4" pipe.  I will probably rebuild the gas train, but I worry a little about removing the burners from the pipe.  

Thanks for the valve recommendation.  I didn't realize they were that expensive, but it's cheaper than a kiln explosion.  I'm a pretty handy guy so the plumbing is in my wheel house. I assume a thermocouple for a water heater will do the job?

I'm just happy that I didn't get a recommendation to scrap the kiln!

Do you have any other recommendations for other safety or convenience features I can incorporate into this design? Would a kiln sitter be feasible, or worth the effort?

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No on the kiln sitter.You need cones and  good glasses for shut off-very simple.

Careful on those burners taking them apart as replacements may not be around most likely.

It very close to my 12  cubic foot updraft from Berman kilns. That has 6 burners that are slightly more Venturi than yours and has a steel pilot ring all around underneath. It has no Baso system . I just keep it on until red heat and then shut down the pilot ring.. It also is 3/4 gas pipe..I do have an digital pyrometer as well as an oxymoron probe  in it for reduction same setup in my car kiln.

Neil says 8 feet from house but since its stucko 4-to 6 would be fine with heat shield- set up some cement board  for heat shield and  leave enough space to walk around it. Keep any combustables far away. I had a friend with one like this in a cement walkway in the 70s that was 6 feet wide-he fired for years-no wood around just stucko and chain link . just be smart about it.

I would test the existing system before scraping it to see how well its working.I'm old but still work well enough to fire.

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maybe stupid but here goes.  i had a friend who had a kiln like this one, maybe not down to the exact model.  she had a metal roof installed just above it about 8 feet high with a slight angle upward away from the house to direct heat away from the brick wall of her house.  when she broke her arm, i loaded it for her.  never had done anything with gas before but i knew the flame needed a path so i staggered the half shelves and sort of spiraled them as i stacked the pots.  she said it was the best firing ever.  just beginner's luck.  

she fired that kiln for her entire long career, her only worry that bugs could get in and make those clay nests that would block the gas lines.  do not know how she prevented that from happening but she had a cover of some kind over the burners.

 genboomxer, do you live where those wasps make mud nests?

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22 hours ago, Mark C. said:

No on the kiln sitter.You need cones and  good glasses for shut off-very simple.

Careful on those burners taking them apart as replacements may not be around most likely.

It very close to my 12  cubic foot updraft from Berman kilns. That has 6 burners that are slightly more Venturi than yours and has a steel pilot ring all around underneath. It has no Baso system . I just keep it on until red heat and then shut down the pilot ring.. It also is 3/4 gas pipe..I do have an digital pyrometer as well as an oxymoron probe  in it for reduction same setup in my car kiln.

Neil says 8 feet from house but since its stucko 4-to 6 would be fine with heat shield- set up some cement board  for heat shield and  leave enough space to walk around it. Keep any combustables far away. I had a friend with one like this in a cement walkway in the 70s that was 6 feet wide-he fired for years-no wood around just stucko and chain link . just be smart about it.

I would test the existing system before scraping it to see how well its working.I'm old but still work well enough to fire.

I have about 2 dozen boxes of various cones for firing. I'm not likely to touch the burners unless I absolutely have to. My side yard is 9 ft wide, concrete, and has no overhanging from the house. I will definitely be getting some backer board for shielding.

Thanks for the tips!

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19 hours ago, High Bridge Pottery said:

Have they used kiln props as burners or is there more shape to them? I can slightly see shape looking from above but hard to tell.

They're not kiln props.  They are made of a ceramic material. The cross section of the cylinder is cone shaped at the bottom, and the top is straight. I think this is designed to create the venturi effect for the gas.

 

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16 hours ago, oldlady said:

maybe stupid but here goes.  i had a friend who had a kiln like this one, maybe not down to the exact model.  she had a metal roof installed just above it about 8 feet high with a slight angle upward away from the house to direct heat away from the brick wall of her house.  when she broke her arm, i loaded it for her.  never had done anything with gas before but i knew the flame needed a path so i staggered the half shelves and sort of spiraled them as i stacked the pots.  she said it was the best firing ever.  just beginner's luck.  

she fired that kiln for her entire long career, her only worry that bugs could get in and make those clay nests that would block the gas lines.  do not know how she prevented that from happening but she had a cover of some kind over the burners.

 genboomxer, do you live where those wasps make mud nests?

 I do live where those type of wasps are.  I will certainly keep an eye open for that. Thank you.

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Looks like it's actually in good shape. No reason it shouldn't fore fine. It would be worth it to clean up the burners with a wire brush and check the orifices.

My similar Olympic came with a small wire brush on a stick brush to clean those bugs out.

No need for a hood unless you just want to keep it covered. 2x4's and some corrugated galvanized sheet would be the cheap and easy way.

Nice old kiln.

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You'll want to move it away from your house air conditioner unit for sure, probably going to want to move it more to the center of that slab.

One thing on my Oly kiln, it fires a good cone hotter on the bottom and I really have to watch it as it can ramp up quickly. The top flue hole  is very sensitive to temperature raising. Consider making a soft brick "chimney" that you can just stack on the lid when you fire it to help the heat draw, using a piece of shelf as a flue cover.

Your bottom shelf should be at least 4-6" from the floor. It's going to take some testing for sure.

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On 1/11/2018 at 6:58 AM, Rex Johnson said:

One thing on my Oly kiln, it fires a good cone hotter on the bottom and I really have to watch it as it can ramp up quickly. The top flue hole  is very sensitive to temperature raising. Consider making a soft brick "chimney" that you can just stack on the lid when you fire it to help the heat draw, using a piece of shelf as a flue cover.

Your bottom shelf should be at least 4-6" from the floor. It's going to take some testing for sure.

Hello Rex,

Thanks for the pointers.  The lid has a damper on top with what are apparently graduated marks scored into the brick  (see image). These graduations are original to the kiln's design and how and when to use them are described in the manual that came with the kiln.  I think I understand from what you're saying that I should build a chimney to extend the flue and damper so as to draw the heat higher inside the kiln.  Of course I will test fire a few times before adding a chimney. It may not be necessary, but if so, is there a height I should start with and work up from there? Sounds like this calibration will be a real 'trial by fire' (ya, bad pun, sorry).

IMG_0109.jpg

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  • 2 weeks later...

Yeah, fire it and see what happens. Lots of messing with the flue for sure.

If you still get too hot on the bottom, try stacking the flue as described. I use about 3-4 tiers of brick on their long sides and put the flue on top.

It is tricky to do this so that junk doesn't fall thru the hole ontp your ware. That's why I use harder fire brick, the type you can by anywhere for fireplaces.

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  • 1 year later...

So here I am, back from the pottery trenches with more knowledge, bruises, burns, and experience!  I got this old girl to fire up for a bisque load and it worked out better than I expected.  I replaced all of the piping not associated with the burners, cleaned out the orifices and replaced the WC gauge. I figured out how to use the pilot ring to help light all the burners, and I engineered a separate pilot light assembly that keeps the Baso valve open.  It's a bit of a dance to get the balance right, but once everything is warmed and going it is quite easy to make adjustments. It's very sensitive the slightest changes in gas pressure too. Candling is a challenge since there are 5 burners, and even at lowest pressure they heat the chamber very quickly.  I just cracked the top open to keep it around 250* - 300*.  She's a little uneven from top to bottom as evidenced from the reference cones.  I estimate about a 1/2 cone cooler at the bottom shelf. I will definitely be experimenting with the flue more the next time to see if I can hit a better balance.  I didn't pack it vey full either so there wasn't a lot of mass to hold/radiate heat. I invested in a digital pyrometer and a new K-type thermocouple too. I kept the t-couple in the bottom 90% of the time because I only have 2 choices and that seemed the more logical.  Additionally, the kiln is really well insulated.  I can stand next to it on a warm day and not be uncomfortable. I mean I can almost put my hand on the outer shell.  It holds heat really well too, because 13 hours after I shut off the gas everything in there was still way too hot to touch. I had to slowly open the lid little by little to cool everything down to unload.

At 7 cu ft it takes me a while to get enough time to make enough ware for a full packing.  I'm retired now so I anticipate that to improve.  Also, I'm looking into getting a used electric kiln about half the size to do most bisque and ^5/6 ox. glaze firings.  I want to use the gas kiln mainly for ^5/6 & ^10 reduction glaze firings. Maybe it's overkill, but I think for the amount of ware I make, and the hassle it is to set up the gas kiln each time it may be worth it just for the bisque firings. I already have an outlet rated for the e-kiln I'm currently looking at.

More questions of the experts - Where can I find a good guide for how to load my kiln efficiently? Or is there a general rule of thumb?  I am getting ready to do some glaze firing with it for the first time, any wisdom or tips on that?  I plan to do a few tests with different clay bodies and glazes, both ^5/6 o&r & ^10 r so I expect mixed results. One more question - the old manual says to place the bottom shelf min. of 6" from the floor, but that puts the shelf about 1" above the bottom peep hole, and makes witness cone placement out of sight and forces me to place the thermocouple below the bottom shelf.  Is there a standard height for bottom shelves?  I haven't seen anything on this topic.

I want to thank all who posted on this all that time back.  You all gave me great advice and thinks to think on. This is exciting and new and feels a bit dangerous too. I feel like a kid with new toys!

Hot Kiln.jpeg

Edited by Genboomxer
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