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Mart

Oil drum gas kiln 2.0 and glazes

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Mart    23

in about 2 weeks I am going to build the oil drum gas kiln.

I have the ceramic blanket (50 mm for 1430C) and I am searching for a burner. They sell those weed burners in harware store and if I do not find anything better, I have to spend 48 EUR on this thing.

 

I have considered 2 options for the kiln design

1) vertical

Something like this:

33jsa6f.png

 

 

2) Horizontal

 

kf3b0y.png

 

I have few round kiln shelves so I am probably going for the vertical design.

 

I like to get it above 1260C. Is it even possible with those simple burners?

 

Because I only have a small electric kiln, I use glazes that work in oxidation. Some of them suppose to work well in reduction too but I like to try something different.

 

Will ash (ash mixed in water) work in gas kiln?

What about salt? Will this ruin the ceramic fiber for good?

 

If you can recommend simple glazes (please, no bright colors or metallic!), please let me know.

 

NB! I am in EU (in really cra**y part of EU) so please, no exotic "US only" materials that will take me 6-8 weeks to get delivered and cost me about 8-10x what they cost over there. By that time, sumer is over and I can forget about outdoors firing.

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Mark C.    1,796

I can help with a few of your questions

I think the horizontal design may heat more even than the straight updraft.

The longer you can keep the flame (draft) in the chamber the more even the heat

 

(What about salt? Will this ruin the ceramic fiber for good?) YES unless you coat it with exoitic expense materials from the US which take time to get.

As far as ash I think its less abrasive than salt.

There was a horizontal made with photos on this site a few months back use the search funtion and see the photos it was also on your side of the pond.

Mark

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Mart    23

I can help with a few of your questions

I think the horizontal design may heat more even than the straight updraft.

The longer you can keep the flame (draft) in the chamber the more even the heat

 

(What about salt? Will this ruin the ceramic fiber for good?) YES unless you coat it with exoitic expense materials from the US which take time to get.

As far as ash I think its less abrasive than salt.

There was a horizontal made with photos on this site a few months back use the search funtion and see the photos it was also on your side of the pond.

Mark

 

 

 

Mark C, i got the idea from Glinum's http://ceramicartsda...bove-650c1200f/

 

Maybe I need to build a saggar for experimenting with salt. I like to use this kiln for more than once or twice smile.gif

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Mark C.    1,796

I can help with a few of your questions

I think the horizontal design may heat more even than the straight updraft.

The longer you can keep the flame (draft) in the chamber the more even the heat

 

(What about salt? Will this ruin the ceramic fiber for good?) YES unless you coat it with exoitic expense materials from the US which take time to get.

As far as ash I think its less abrasive than salt.

There was a horizontal made with photos on this site a few months back use the search funtion and see the photos it was also on your side of the pond.

Mark

 

 

 

Mark C, i got the idea from Glinum's http://ceramicartsda...bove-650c1200f/

 

Maybe I need to build a saggar for experimenting with salt. I like to use this kiln for more than once or twice smile.gif

 

 

Thats the one.

I have a salt kiln with a fiber roof and door and it needs spray coating repair almost every fire. Salt eats it up.

Mark

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Mart    23

How complicated is it to achieving and even reduction in a vertical updraft kiln like this?

What if I make the design more complicated, buy bringing the exit to the bottom of the kiln and adding a external "chimney". I like to use only one burner. Can this be done with one burner at the bottom and at the opposit side of the flue?

 

post-19541-137112118096_thumb.jpg

 

 

I am not really exited about the horizontal design because it's a huge waste of kiln space.

 

BTW, to make it easy to transport, I think I am going to skip the oil drum and use something like chicken wire, to hold it all together.

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Mark C.    1,796

How complicated is it to achieving and even reduction in a vertical updraft kiln like this?

What if I make the design more complicated, buy bringing the exit to the bottom of the kiln and adding a external "chimney". I like to use only one burner. Can this be done with one burner at the bottom and at the opposit side of the flue?

 

post-19541-137112118096_thumb.jpg

 

 

I am not really exited about the horizontal design because it's a huge waste of kiln space.

 

BTW, to make it easy to transport, I think I am going to skip the oil drum and use something like chicken wire, to hold it all together.

 

 

The verticla updraft is an uneven temeture design-as well as reduction.

Your drawing is showing a traditional downdraft design which fires more even and has even reduction.This also uses heat more efficiently.

The only issue is will one burner fire whatever space it is?

Mark

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Mart    23

How complicated is it to achieving and even reduction in a vertical updraft kiln like this?

What if I make the design more complicated, buy bringing the exit to the bottom of the kiln and adding a external "chimney". I like to use only one burner. Can this be done with one burner at the bottom and at the opposit side of the flue?

 

post-19541-137112118096_thumb.jpg

 

 

I am not really exited about the horizontal design because it's a huge waste of kiln space.

 

BTW, to make it easy to transport, I think I am going to skip the oil drum and use something like chicken wire, to hold it all together.

 

 

The verticla updraft is an uneven temeture design-as well as reduction.

Your drawing is showing a traditional downdraft design which fires more even and has even reduction.This also uses heat more efficiently.

The only issue is will one burner fire whatever space it is?

Mark

 

 

Max internal height I can have is 610 mm, kiln shelves I have are 350 mm diameter and if I leave 50 mm (~2 inch) between the shelf and the internal wall, I'll have a cylinder 61*3.14159*22.52= 97016/1000 or 97 liters (205 pints, 102.5 quarts, 3.426 ft3 or 25.62 gallons... wacko.gif huh... Yes, metric system rules smile.gif

 

Cool, this is bigger than my electric kiln I have

 

I can actually make it bigger (max diameter 500 mm and I still have about 1.5 mm of blanket left for the bottom and the lid) but I do not want to buy new kiln shelves for something as experimental as this.

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Mart    23

I finally have all the parts to build the kiln.
Before I do that, I like to ask for some advice.

 

post-19541-0-73887200-1373104211_thumb.jpg

 

Hopefully this makes sense :)

 

I have 2 burners, 114 kW each and at full blast and 4 bar pressure, those will burn 8.25 kg of gas per hour.
Probably a total overkill but we will see. :)
I made a exhaust exit thingy... flue? and also 3 clay pipes for the chimney.

post-19541-0-76156500-1373102838_thumb.jpg

post-19541-0-38057100-1373102275_thumb.jpg

 

Burners are upside down on those pictures. Do not mind that.
 
Q 1; If my burners diameter is 60 mm, what is the recommended hole size? Will 80 mm be enough?
 
The back wall will be straight and front wall will be curved because I only have 350 mm kiln shelves.
 
 post-19541-0-05598700-1373102909_thumb.jpg

Q 2 : Do I need to close up the "X" and "Y" area, so the exhaust can exit only from the "front" of the lowest kiln shelf?

 

 

post-19541-0-38057100-1373102275_thumb.jpg

post-19541-0-76156500-1373102838_thumb.jpg

post-19541-0-05598700-1373102909_thumb.jpg

post-19541-0-73887200-1373104211_thumb.jpg

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Biglou13    202

I think you may have a problem with exhaust flue. And Chimmney pipes.

 

Exhaust flue size needs to be some what specfic but I think yours are too small.....

 

I'm also doubting how refractory, your flue and chimney is....and it wil take the stress of repeated firings

 

I believe there is a formula for flue size and Chimmney size, ill look for it.

 

How are you sealing flue to kiln.?

 

Damper?

 

I'm slowing collecting parts for a build....

I can appreciate the work your doing here!

I looking forward to you finishing it.

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Mart    23

Diameter for the chimney opening is 10 cm (3.93") or 78 cm2. The square flue thingy opening is about 14 cm wide and 4 cm high at kiln side (14*4=56 cm2).

Estimated volume will be about 95 liters.

 

> believe there is a formula for flue size and Chimmney size, ill look for it.

 

Thank you.

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Mart    23

I think you may have a problem with exhaust flue. And Chimmney pipes.

 

Exhaust flue size needs to be some what specfic but I think yours are too small.....

 

I'm also doubting how refractory, your flue and chimney is....and it wil take the stress of repeated firings

I am not worried about that for start unless it can not last 2 firings. This whole thing is more like a prototype working prototype but obviously I like to get some results.

 

 

 

I believe there is a formula for flue size and Chimmney size, ill look for it.

 

How are you sealing flue to kiln.?

I found something: http://www.potterswithoutborders.com/2012/07/lpg-burner-calculations/

 

Reading it right now.

 

because the fiber is "soft" I'll just cut a smaller hole and push it trough the wall really carefully. If needed, I'll add small strips of fiber around the flue/wall hole.

 

 

 

Damper?

 

I'm slowing collecting parts for a build....

I can appreciate the work your doing here!

I looking forward to you finishing it.

I'll use an old brick as a damper or something lighter.

Edited by Mart

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Mart    23
A rough rule-of-thumb ratio is one square inch of flue area to 8,000 BTU’s of maximum gas input

 

 

Lets use 18,500 and 20,000 as Btu/h for calculations.

90 liters to ft3 = 3.17 cubic foot

 

A) 3.17*20000= 63400 Btu/h.

    Flue area 8000 Btu/h per inch2 or 63 400/8000=7.92 or 7.92*6.4516=51.09 cm2

 

B) 3.17*18500= 58645 Btu/h

    Flue area 8000 Btu/h per inch2 or 58 645/8000=7.33 or 7.99*6.4516=47,29 cm2

 

If those calculations are correct, the flue thingy is OK.

What I am actually worried about, are the burners. Those are 114kW (388 984 BTU/h) and I have 2 of those.

I have no plans to mess around with fast firing raku stuff. Can those burners function at 1/10 of max power output?

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Mart    23

what is " refractory material" ? Clay I used has lots of grog in it and can take 1300C (2372 F)

If I had to build it again, I'll make it a lot thicker and probably use heat shock resistant clay too. 

 

Thank you for your advice btw.

Cheers!

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Mart    23

I started to build it today

1) Made a wire frame 

 

post-19541-0-18557200-1373648343_thumb.jpg

 

2) made sure it's shaped OK with my 1:1 drawing

 

post-19541-0-54332300-1373648385_thumb.jpg

 

3) Time to cut the ceramic fiber blanket

 

post-19541-0-54469300-1373648431_thumb.jpg

 

4) After I had the kiln floor cut out, I measured the holes for the burners, cut the holes.

I had to add extra 5 cm to of "chicken wire" to the top because I decided to have the outer walls rest on the floor piece.

 

post-19541-0-85917400-1373648635_thumb.jpg

 

5) Kiln lying on it's back. Floor panel is covered with kiln wash. Just in case :)

BTW, I am thinking about covering the walls too. This seals up the fiber and I think it will reduce the amount of dust. Are there any  reasons not to?

post-19541-0-82119100-1373648818_thumb.jpg

 

BTW. I made the clay buttons too but I am not sure do I even need them for the walls. Looks like everything is staying in place and it's not sagging form anywhere.

Now I have to make a lid and fire it up. It's going to sit on fire bricks, lifted off the ground so burners have plenty of space and lots of air.

I'll be completing this probably on Monday, because I need to get the propane gas but the shop is closed on weekends.

post-19541-0-18557200-1373648343_thumb.jpg

post-19541-0-54332300-1373648385_thumb.jpg

post-19541-0-54469300-1373648431_thumb.jpg

post-19541-0-85917400-1373648635_thumb.jpg

post-19541-0-82119100-1373648818_thumb.jpg

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neilestrick    1,379

The problem with the flue thingy is not so much about it handling the temperature, but rather handling the unevenness of the temperature. Clay bodies for making pots are not really made to withstand being really hot on the inside but not the outside, and really hot at one end and cooler at the other. My bet is that it will crack in the first firing. What you really need is a flue thingy built from kiln shelf material.

 

Those burners are really large for the kiln. Maybe try to redesign with just one?

 

Use the buttons. That fiber could sag during firings otherwise.

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Mark C.    1,796

I would use buttons as well as the fiber can sag.

The flue sould be bricks or shelves I agree that the clay flue will die /crack 1st fire or so.It's the week spot in this setup/design.

With those two burners this should get to temp very fast so try and go a little slower.

Mark

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Mart    23

Thank you both foe all the advice.  I am thinking about making the flue out of same fiber as the kiln. Hopefully I can find a small piece of 25 mm (I only have 50 mm) and just make a flat pipe out of it. In this case, the outside part of the flue will be made of fire bricks and my chimney will sit on top of those.

 

Fiber blanket is soft. Using half bricks (lying flat) is an option to support the first shelf better than 4 posts. Those will close the X and Y too while giving me the required clearance for the flue. 

 

BTW; each burner has a separate valve so I can probably get them running as even as possible and as slow as possible for start. I have designed the hole thing so that I can move the burners closer to the kiln openings as the temperature rises.

We will see, what happens on Monday :)

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Mark C.    1,796

You can split the fiber into thinner pieces very easy-just use a knife or sharp edge to start. 50mm will split to 25mm easy. Cut what you need and then slit it remembering you will have twice as much.Do not breath the fibers (wear a mask) when doing any fiber work

Mark

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Mart    23

--- snip ---

 

Those burners are really large for the kiln. Maybe try to redesign with just one?

 

Use the buttons. That fiber could sag during firings otherwise.

 

Any ideas how?  :)

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Mart    23

neilestrick, I tested out one of the chimney pipes and after about 1 hour, it cracked and I replaced it with ceramic fiber tube.

I also did not use my home made "flue thingy". Instead, I used 2 thin fire bricks as a support for the bottom shelf and made a half pipe out 25 mm fiber to direct the exhaust out to the brick chimney. 

 

Anyways, the results for our first firing where awesome. Porcelain looks so much better if fired in gas kiln. 

We started out really slowly with a smallest flame possible for about 1 h. Then started to increase the flame slowly. 

After about 9 hours and maybe 9-10 kg of gas the prssure got too low and we decided to stop.

We had additional 11 kg as backup but we decided not to use it. It was probably a mistake because we did not reach cone 7. :(

 

post-19541-0-93426000-1374310770_thumb.jpg

 

Few changes I have to make. 

1) Because the fire bricks, inside the kiln, sank to the floor, the flue opening shrank too. I need to use 2 more thin fire bricks as a "floor" for the flue inside the kiln.

 

2) Lift the kiln higher off the ground so I we have more room to play with the burner distance. 

 

3) Probably spend some more money and buy lower temperature 50 mm 6.5 mm (and put 3 layers) blanket to make the walls thicker. All I need to do is open up the wire cage and wrap it around the existing kiln body. Front part of the kiln has a overlap so it is not a problem. 

 

4) Borrow a kiln pyrometer. Sight and smell will not do it yet :)

post-19541-0-93426000-1374310770_thumb.jpg

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Mark C.    1,796

As you have found out to reach cone 7 you will need thicker walls. For my cone 11 kilns I use at least 6-to 7 inches of fiber.

 

Now that you have fired the fiber it will be a bit more brittle now so be extra carefull when handling it. 

 

Those glowing walls really show how hot and thin the walls are.

Mark

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Marcia Selsor    1,301

If you are going 1260 C I would use the thicker fiber. You'll need that insulation. This is an old portable kiln with 1 inch of fiber  at 1800 F. You can see the buttons through the hot fiber. The kiln is made of hardware fabric  1/4" holes. You can see how hot it is. Go for as much insulation as you can get in there.

 

Marcia

 

 post-1954-0-04145700-1374361795_thumb.jpg

post-1954-0-04145700-1374361795_thumb.jpg

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Mart    23

Marcia, that kiln looks almost transparent :)

I used hardware cloth too for the exterior (I just did not know how it was called in English). Excelent material for something like this.

Looks like I am going to drop another 40 EUR on this an buy a box of 6.5 mm (1/4") low temperature (ceramic fabric 1260ºC (128 kg/m) and wrap 3 layers around the kiln body and reuse my hardware cloth cage.

Or I have to cough up 70€ and get 25 x 610 x 7320 blanket and use that.

 

PS! Forum administrator, can you please change the thread topic to: "Ceramic fiber / hardware cloth gas kiln 2.0"

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