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Advice on repairing L&L kiln bottom


Tabathos
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Hello, thanks for reading. 

Got myself an used econo kiln L&L. Wall bricks are in great condition, also the lid. The only 'if' is the bottom, it is damaged as shown in the pictures. 

What are the steps I should take to repair it? Some spaces between bricks are loose, so I don't know if I should fill them with kiln cement first (well, but after scrapping all the scraps). 

The bricks are in good condition, is the surface that looks so messy (and the space between them worries me a little). 

Thanks in advance, my best regards. 

Screenshot_20201225_223750.jpg.89b158d10496ddf743634b2519c72dc9.jpg

Screenshot_20201225_223736.jpg

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Hi Tabathos,

The second photo is the upside? If so, looks like it has been protected by a kiln shelf - the typical advice being to set the bottom shelf on half inch (1.27 cm) posts.

Any road, likely the advice you get here will be just that, also support the kiln with a sturdy stand that spans the entire bottom - supplement the typical angle stock stand with a sheet of metal the same shape/outline of the bottom. Use material that is thick/strong enough to distribute the load.

Is the top photo the underside? If so, the rusty rectangle stain indicates a kiln stand that has lost its galvanize and began to rust; check it over carefully, for the top portion of the typical stand will rust away to the point of failure, given enough time and exposure. I repaired my stand by bolting on eighth inch thick angle stock below the rust line, for the material in contact with the kiln was mostly rusted through. I'll post a pic of the repair later... 

Edited by Hulk
half inch posts, .125 thick angle stock
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4 minutes ago, Hulk said:

Hi Tabathos,

The second photo is the upside? If so, looks like it has been protected by a kiln shelf - the typical advice being to set the bottom shelf on one inch (2.54 cm) posts.

Any road, likely the advice you get here will be just that, also support the kiln with a sturdy stand that spans the entire bottom - supplement the typical angle stock stand with a sheet of metal the same shape/outline of the bottom. Use material that is thick/strong enough to distribute the load.

Is the top photo the underside? If so, the rusty rectangle stain indicates a kiln stand that has lost its galvanize and began to rust; check it over carefully, for the top portion of the typical stand will rust away to the point of failure, given enough time and exposure. I repaired my stand by bolting on quarter inch angle stock below the rust line, for the material in contact with the kiln was mostly rusted through. I'll post a pic of the repair later... 

Thank you very much for your detailed response. Yes, the rusty one is the bottom of the bottom. I have a stand that is made of pieces of metal, not the ones that have a sheet of metal with a hole in the middle. 

The upper side is the clean one, and yes, it have been used with a shelf. Then, should I only apply a coat of kiln cement? The woman who sold it told me it worked fine the way it is, but a fellow ceramist told me that it should be repaired and fired the whole bottom in a bigger kiln. I'm not sure of that,

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Aye, there are several threads here where damaged kiln bottoms are discussed, e.g.

Cracks in kiln floor - Equipment Use and Repair - Ceramic Arts Daily Community

My kin bottom is in fairly good shape, structurally (there's lots of glaze damage), hence I didn't add the sheet of metal, however, the stand is in bad shape. Here's a pic of the bolted on angle material. The original stand is sound where the bolts are, however, the portion that touches the kiln is almost completely rusted away.

Likely you'll get more responses over the next few days ...in the meantime, try searching "sheet metal" for parallel threads.

Note, the typical recommended post for the bottom shelf is half inch (edited, above).

 

repair.JPG

Edited by Hulk
see edit, link test and reset...
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37 minutes ago, Hulk said:

Aye, there are several threads here where damaged kiln bottoms are discussed, e.g.

Cracks in kiln floor - Equipment Use and Repair - Ceramic Arts Daily Community

My kin bottom is in fairly good shape, structurally (there's lots of glaze damage), hence I didn't add the sheet of metal, however, the stand is in bad shape. Here's a pic of the bolted on angle material. The original stand is sound where the bolts are, however, the portion that touches the kiln is almost completely rusted away.

Likely you'll get more responses over the next few days ...in the meantime, try searching "sheet metal" for parallel threads.

Note, the typical recommended post for the bottom shelf is half inch (edited, above).

 

repair.JPG

Thank you very much for the much needed information. That repair of the stand looks great. 

Just found a tinsmith near to my house, so gotta go when I get back to work in January.  Any recommendation on the material? I know about metal, but what kind of metal? Tried searching on the website, but didn't find it. 

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Good question! The idea (not my idea, have read "sheet metal" advice on this forum many times) being to support the kiln bottom better, that is, distribute the load evenly over more area, particularly, supporting the weight of the walls, and also the ware, both which are typically well outside the footprint of the stand.

Just putting a sheet of thin metal over the stand would not offer much additional support near the walls of the kiln, where it's needed (unless the sheet material is rather thick - and expensive), although the center of the kiln would be better supported...

Hmm, the L&L stand is described thus "The kiln stand is made of 14 ga. aluminized steel..." - however, said sheet is bent ninety degrees at the edges, which stiffens it quite a bit, see below.

I'll have to punt the design back to you, but will offer this - I'd consider bolting on angle stock, similar to what I did (image above), except extending two of the parallel pieces to run out to the edge of the kiln, and wider material, perhaps 2 inch (mine is 1.125 inch). In my case, the stand's contact area with the kiln was more than doubled, and, perhaps more important, was broadened as well. Should you do something like that, be sure to round the corners and edges against brushing your ankle against it, ouch.

As for material, the angle I chose is just plain carbon steel; at .125 inch thick, it won't rust fast enough to be a concern for a very long time - and I'm watching it.

proper.JPG

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@Tabathos Good advice from Hulk. Get some sheet metal under it that supports the whole floor. Another option would be to ditch the stand and instead set it on cinder blocks that support the whole thing. More of a trip hazard that way, but cheaper. Set the blocks so air can flow through them horizontally. If you have a downdraft vent, attach it to the side of the kiln. 

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  • 4 weeks later...

Update on the topic: the technician came to check both of my kilns, and said the damaged floor kiln would work just fine. Said he had a big STOP sign he would give me to put it under the kiln, pretty cool, isn't it? Also said he would quote a reparation for the floor, but have to hear from him again. The other kiln needed some rewiring, and fGs!, elements are so expensive! If I had to rewire all the 8 elements, gonna surpass the price I paid for my little kiln. 

He also went almost insane checking the wiring. Apparently that kiln was somehow adapted to work as a glass kiln, so had to check it out throughly. Haven't had the opportunity to fire it, but I'm gonna do it soon. 

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9 minutes ago, Tabathos said:

Also said he would quote a reparation for the floor, but have to hear from him again.

Repairing that floor isn't really possible. Mortar will not hold them back together. Just scrape down any loose stuff on the surface, and do another skim coat of mortar. The bricks can't go anywhere with the stop sign underneath and the metal band around the edge.

11 minutes ago, Tabathos said:

Apparently that kiln was somehow adapted to work as a glass kiln, so had to check it out throughly.

Using it as a glass kiln shouldn't change anything in the wiring or elements. Good to have it all checked out, though. Most of these old Econo-Kilns I work on need new wiring. The old wires are usually pretty brittle, or they have the old waxy wires and the covering has degraded. So unless they're in perfect condition, which is rare, I rewire them with modern insulated wire so there's no safety issues.

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2 minutes ago, neilestrick said:

Repairing that floor isn't really possible. Mortar will not hold them back together. Just scrape down any loose stuff on the surface, and do another skim coat of mortar. The bricks can't go anywhere with the stop sign underneath and the metal band around the edge.

Using it as a glass kiln shouldn't change anything in the wiring or elements. Good to have it all checked out, though. Most of these old Econo-Kilns I work on need new wiring. The old wires are usually pretty brittle, or they have the old waxy wires and the covering has degraded. So unless they're in perfect condition, which is rare, I rewire them with modern insulated wire so there's no safety issues.

Actually that was what he said about the floor repair, but I guess I can actually do it myself. Gonna get some mortar and have some fun. 

And about the wires, I don't know what he said because I don't understand electrical things lol, but apparently the upper module of the kiln was adjusted to bring more electrical power, or something alike. Glass kilns are designed to bring more heat from the top, apparently they tried to compensate for it. 

Wires are OK. The previous owner said she changed them before selling it to me. Well, just before she went to a seven years hiatus, and then decided to sell the kiln. 

I'm gonna post an update later, it is so exciting to learn about kilns. Thank you so much about your reply. 

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I notice that the rail rust indicator on the bottom is off center, if this is so, it also created more stress on the floor. I would certainly make sure that the base is centered up next time on the metal stand. 

I have also seen a firebrick base built using firebrick, and angled steel bolted together to hold it in place. This was a square base used on an octagonal kiln, but did not have any movement or anything so it did not matter the shape, as long as it is larger than the smallest outside diameter of the kiln wall.

 

best,

Pres

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1 hour ago, Tabathos said:

gonna surpass the price I paid for my little kiln

I paid £25 for my kiln.  Then new wiring, then new  elements as other half didn't realise elements would be brittle. 

Several years later added a digital controller.

Still less ££s than a new kiln.

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On 24/1/2021 at 9:50 AM, Pres said:

I notice that the rail rust indicator on the bottom is off center, if this is so, it also created more stress on the floor. I would certainly make sure that the base is centered up next time on the metal stand. 

I have also seen a firebrick base built using firebrick, and angled steel bolted together to hold it in place. This was a square base used on an octagonal kiln, but did not have any movement or anything so it did not matter the shape, as long as it is larger than the smallest outside diameter of the kiln wall.

 

best,

Pres

Thank you very much, I did it just as you said. 

On 24/1/2021 at 11:14 AM, Chilly said:

I paid £25 for my kiln.  Then new wiring, then new  elements as other half didn't realise elements would be brittle. 

Several years later added a digital controller.

Still less ££s than a new kiln.

Certainly new kilns are pretty expensive! It is cool we are able fo find used kilns at an affordable price. 

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Update: just put the kiln on its new repurposed sheet of steel, and it looks great. Also bough a vacuum, and vacuumed most of the kiln wash that was on the walls of the kiln. 

Some questions: is it normal for the coils not glowing? Just put a glaze load, and it is certainly heating, but I can't seem to see a glow. Also the bottom peephole is kinda cool, in comparison to the upper one, that is really hot. 

I don't know why my technician says that my kiln is "weird", compared to the others. He says that the electric diagram is different, but who knows. 

Thanks in advance, my best regards. 

Screenshot_20210127_163638.jpg

Edited by Tabathos
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If I can suggest the wires that jump between boxes look like they need attention, especially the holes without bulkhead connectors. If it were mine I think I would attend to them sooner than later and make them more code approved so to speak. High temp wire run inside flexible metal conduit with the proper connectors at the cabinets is probably a reasonable solution.

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36 minutes ago, Hulk said:

That looks sturdy Tabathos!

May I suggest knocking back (rounding off) those corners - quite a bit, like a 5 mm radius or so - against catching a leg (and any sharp edges as well).

Thank you very much for your response. I would do that. 

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2 minutes ago, Bill Kielb said:

If I can suggest the wires that jump between boxes look like they need attention, especially the holes without bulkhead connectors. If it were mine I think I would attend to them sooner than later and make them more code approved so to speak. High temp wire run inside flexible metal conduit with the proper connectors at the cabinets is probably a reasonable solution.

Ok, ok. I'll comment it with the technician. This kiln is a really old econo kiln kr18, gotta contact the company for more information. 

Current mood: watching the kiln and feeling that it is slow at gaining temperature. What would you people do? My other kiln, at this point would have had the cone bent, but I feel like this one is slowww. 

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1 hour ago, Tabathos said:

Ok, ok. I'll comment it with the technician. This kiln is a really old econo kiln kr18, gotta contact the company for more information. 

Current mood: watching the kiln and feeling that it is slow at gaining temperature. What would you people do? My other kiln, at this point would have had the cone bent, but I feel like this one is slowww. 

If the current setup isn't matching the wiring diagram, that may be the problem. It's always an adventure when you get a used kiln, as you never know what the former owner did to it. That top switch isn't original, or at least the knob isn't. This kiln is a pretty typical setup, though, so it should be easy to get it back to functional, but that may mean new elements and wiring in the box.

Judging by the external jumper wires, you should take a good look at the condition/quality of the internal wiring in the boxes and consider replacing all of it. If I was the tech that looked at this kiln, I wouldn't have touched it without you agreeing to replace the sketchy wiring. Those external wires definitely need attention, and he shouldn't have left them in that condition because they are not safe. The wires are really old, and don't have the proper safety connections. The originals connections were likely jumper cords with plugs, similar to how they make the Jupiter kilns today (see photo below). I can't tell from your photo if the outlets/receptacles should be in the middle section or in the top and bottom sections, but both the top and bottom sections connect to the middle section via the jumper cords. Based on other kilns I've seen, I would expect the cords to come from the top and bottom sections, and plug into the middle section.

L&L should be able to tell you how it was set up originally, although it's possible it's so old they don't have records any more. I've run into kilns like that before. Even if it's not set up like original, it needs to be set up safely. That means quality jumper cords that have proper strain relief so the wires can't be pulled loose. Personally, I would not hard wire the sections together if there are already holes in the boxes to accept outlets for the jumper cords. But if you can't figure that out, then metal conduit between the sections and high temp wire would be the way to go.

Jupiter.jpg

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