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My dream was to build my own kiln for wood firing for high temperatures stoneware.  Step by step, year by year, first the shelter then foundations. Now is high time for building the kiln itself. I've just started.

You can see the design and some pictures below. I would be grateful for your comments and concerns. This is my first kiln and I have a number of questions and uncertainties. For example

Shouldn't the ceiling arch be closer to regular circle or catenary?

I use clay with grog and high alumina hard bricks. Should I use any extra special mortar for the arch?

Is the chimney  sufficiently wide?

Pawel

My-kiln-25-05-2019-09-46-p4.jpg

 

My-kiln-25-05-2019-09-46-p3.jpgMy-kiln-25-05-2019-09-46-p2.jpgIMG_5489.jpgIMG_5497.jpgIMG_5501.jpgIMG_5505.jpgIMG_5512.jpg

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congratulations on summoning up the courage to get started!

i assume that the numbers are measurements, do you use metric in Poland?

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you probably already have this book but just in case.....https://www.amazon.com/Kiln-Book-Frederick-L-Olsen/dp/0812221869

prob lots of answers in there :)

I used to have a gas burner ca ternary arch brick kiln and i had to reduce the size of the flue opening - a friend helped me - I probably should have read the book!

Edited by terrim8

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thanks for replies

@oldlady yes, we use metric system, the dimentions on the drawings are in cm.

@terrim8 Unfortunately I have not read that book, but I will buy it now. It is a bit late for fundamental changes because I'm going to continue my work on Monday.  My main source of knowledge was the reading of Ian Gregory "Kiln building", but it is not too much detailed.unfrotunatelly

@Rae Reich My arch is going to follow regular circle (180 degrees). What kind of bracing, which you mention, would be needed? Should I rather turn again into more tall and narrow catenary curve?

I do not plan to cut the bricks into wedges, just fill the upper gaps with clay in regular distances. Will it work?

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The cement blocks in center will not take the heat -especially from one layer of hard brick-3 layers would be needed.Just make the whole thing(the cement blok area) out of hard brick. 

The arch needs to be supported at area where the wall comes up and the arch sits in top.Thats where you need steel Bracing

I like a mortar with less clay content ,high grog content and more high temp materials -along with some vermiculite -Hopefully your clay can take the heat. You could add alumina as well.

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@Pawelpksa The cement blocks are either going to spall (explode) or calcine and fall apart. Since they are essentially inside the kiln, they will not be able to handle the heat, especially with only one layer of hard brick covering them. Even with 3 layers of hard brick I wouldn't trust them to do well inside the kiln like that. When we use cinder block under the kiln, they can cool off because they have openings that allow air flow. You should build the entire pedestal out of kiln bricks.

You'll need 3 layers of hard brick for the floor, and they should be up on cinder block as well, or you're going to spall the concrete slab. I've seen the results of a kiln built directly on a slab- not good.

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thanks, it means that I have to make changes to rescue this project..

so the pedestal will be built again

regarding the floor - what if I just add ceramic fibre blanket and than additional layer of hard bricks, would it be ok?

I wonder if the ceramic fibre blanket (13mm) isn't too soft (it is going to bear some weight). Shouldn't I use some hard ceramic panels?

Edited by Pawelpksa
adding more

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33 minutes ago, Pawelpksa said:

I see, ok, so the pedestal will be built again

regarding the floor - what if I just add ceramic blanket and than additional layer of bricks, would it be ok?

If you put blanket between the layers of brick, it will compress and lose its insulating benefits. It really should be on cinder blocks for air flow.

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Since you have already build this much .You could add a layer of soft brick to floor that is exposed and then another layer of hard brick on top so the 3 layers is there .

3 layers is the minimum and on a slab . I have seen a slab crack and explode during a fire-not pretty

Edited by Mark C.

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I really appreciate you advice. I progressed so much and now start loosing motivation. It is a painful learning process.
Putting that all now on the cinder blocks would mean ... dissembling all. I thought about adding cinder blocks on top of the existing floor and then adding a new floor on top of it. But that would mean that the chimney needs some changes as well. Ahh..
In that case, should the chimney stand on cinder block basis as well?  @neilestrick

@Mark C. what kind of soft bricks you mean?
Following your idea, would it be good to use ceramic panels (25mm, 1260 Celcius) and than 2 layers of hard brick on top?

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My thought at this point would be protect the concrete so maybe soft brick with hard brick on top. Hard brick has very little R value (Thermal conduction U, likely for your location) so you may find one layer of soft and one layer of hard over the top has as much or greater thermal resistance as three layers of hard brick.

if that did not work out, then there are other more exotic ways to get greater insulation with less overall height but their costs are usually an issue.

short of all that it might be worth the effort to take it apart clean and restart. As far a the steel frame, easy to come up with a simple one sporting full moment joints that’s easy to weld up.

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Don't lose heart, @Pawelpksa, starting over now with good advice will save your money and time and pots! You have been very thoughtfully building this kiln, unfortunately without the knowledge of the frailties of overheated cement and concrete. Please give your careful attention to this problem.

Rae

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soft brick are whats in electric kilns-very light-and insulating. they come is various temp ranges called K so a k23  is rated for 2300 F

k25 ,k26 and K28s all getting hotter abnd holding up well.

You would need at laest 3 layers of the 25mm hard fiber board to equal a soft brick which is the same size as your hard bricks

Really the best way would be start over but adding to the floor could work if that does not impede your air flow. You have got to get rid of those cement blocks inside kiln as they will be toast after one fire.

Edited by Mark C.

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Dear,

OK, so I'm going to start it again.

1. Should the chimney stand on the cinder blocks base as well?

2.  Should I use any special type of cinder to resist the pressure of the entire kiln? I have the following options:

- cinder block for walls (8MP, beton and gravelite) pk-19.jpg

- ventilation cinder Pustaki-kanaly-wentylacyjne-keramzytobet

- cinder block for walls (without gravelite) 

- gravelite block 3200_dzialowe12.jpg

cinder block for ceilings (terriva) 8bab82c892d6dc03c8b48e20b8d19bd2.jpg

porotherm blocks (ceramic) used for walls pustaki-ceramiczne-porotherm-profi.jpg

Edited by Pawelpksa
extra sentence

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I like to use ventalation cinder blocks-then I put down a thick piece of expanded metal 1/4 to 3/8 inch on the brick tops to make a flat solid surface. That way you can lay them a bit apart for air space between them. Then add the floor layers.

I have two kilns made with cinder cinder bloks -one they are sticking up the long ways so the base is higher to help with loading. This is my salt kiln with a front loading door

My car kiln the cinder blacks are laid down the narrow ways as the car need to be lower.

And yes the chimmney need to be on the same level with blocks under it.

Edited by Mark C.

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All good suggestions but if the opportunity presents itself and possible I like to have some insulation between the cold surface and super hot which generally means one layer of IFB on the block, interior only,  supports go all the way down to the block. One or more layers of hard brick over the IFB, whatever you are comfortable with. Why let all that heat escape through the floor. Only means more propane and operating expense for the owner every single firing.

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Since soft brick may not be available to you a layer of hard brick for the 1st layer then some layers of that ceramic board you talked about -at least 2.5 inches then another layer of hard brick for the final floor layer.

I used 1 layer of hard brick then a layer of soft brick then a layer of hard brick for my salt kiln floor. Its cool on bottom.

The idea is to insulate and keep the heat inside kiln. The wood kiln floor will realkly get hot with the coals.

Edited by Mark C.

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Thanks for all posts.

Following your guidance I dismounted what have you seen already. It’s painful process. I will not stand it again. It was tidious work and a long day.

could you help me to avoid another mistake?

should I use mortar for the floor and for the chimney or not? 

Proof

BE3BFE92-1FC7-4302-AD4F-E31C3406459A.jpe

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