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A New Kiln Conversion Project: What Would You Do?

kiln conversion soda chimney

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#21 Chantay

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Posted 24 September 2013 - 12:22 AM

I have read about and heard from another potter about washing the inside of the kiln (for soda/salt) with a glaze.  I think Robin Hopper did this using a shino.


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#22 Mart

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Posted 24 September 2013 - 01:54 AM

Why do you like to spend energy (BTU, kWh) for heating up that bag-wall? :)

Will this work, if you send flames straight up?

This is a 3 min quick sketch, I hope it makes sense. What do you guys think, will this work? (I forgot the salt/soda opening)

 

Attached File  CD_kiln.jpg   56.14KB   1 downloads

 

Now you will have a bit less than 29 stetson hats of space but still more, than on the drawing you had. I am not telling, your idea is wrong but it looks like something you want to use when building a wood fired kiln.

Every brick you place inside the kiln, needs to be heated up. There is no way around it. 

 

NB! Kristin, pay really close attention to page 21 in The Art of Firing ;)



#23 neilestrick

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Posted 24 September 2013 - 09:15 PM

Why do you like to spend energy (BTU, kWh) for heating up that bag-wall? :)

Will this work, if you send flames straight up?

This is a 3 min quick sketch, I hope it makes sense. What do you guys think, will this work? (I forgot the salt/soda opening)

 

attachicon.gifCD_kiln.jpg

 

Now you will have a bit less than 29 stetson hats of space but still more, than on the drawing you had. I am not telling, your idea is wrong but it looks like something you want to use when building a wood fired kiln.

Every brick you place inside the kiln, needs to be heated up. There is no way around it. 

 

NB! Kristin, pay really close attention to page 21 in The Art of Firing ;)

 

A bag wall is often necessary to make the kiln fire evenly. In a kiln that size it probably won't need to be more than 4.5" (1 brick on its side) tall, so that's only 3 bricks for the bag wall. In a kiln that already has over 200 bricks, that's only 1.5% more bricks, so it might cost another 50 cents in gas costs at the most to heat those up. You'd probably waste more gas trying to even out the temperature without them.


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#24 neilestrick

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Posted 24 September 2013 - 09:18 PM

Personally, I'm not a fan of burners coming up from the floor, for two reasons. First, it makes them difficult to adjust. I don't particularly like having to lay on the floor to adjust my burners. Second, they can get crud falling into them, and cleaning them out can be difficult because they're under the kiln. Go in from the side, with a short bag wall, and save yourself some grief.


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#25 Mark C.

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Posted 24 September 2013 - 09:38 PM

I'm also not a fan of burners up thru the floor-My updraft has them and when something falls into them its a pain to fish it out. Also without a bag wall there are HOT spots that do not need to be there. Many manufactures use this system as the sacking splace is bigger-not better just more for less bricks used. The corners where that flame comes up are always hot spots. The bag wall keeps this heat way more even.Neil summed it well above.Bag walls make for more even firing and less hot spots.

Mark


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#26 JBaymore

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Posted 24 September 2013 - 10:11 PM

The cheaper the burners... the less primary air they entrain and the less efficient the mixing activity they produce.  Industrial high velocity burners can be used without any bag walls or even most any consideration to the location of the burner on the chamber...... fire from one corner, top down, bottom up, whatever.  The typical potter level burners .....no so much.  Even forced air.

 

The bag wall will help to not only divert the flame / hot gas path to distriubute the heat energy approprioately to the circulation pattern of the particular design, but will also contribute ot assisting with the post burner mixing action (getting the air and gas in intimate combination to promote good combustion and an even atmosphere in the chamber).

 

Bottom up without a bag wall will result in a very uneven heating patern in that particular layout.

 

Plus one of the "de sign criteria" that was mentioned as "directionality" of flame path.  Firing into the stacking will help with this.

 

And all of the above recent comments are so true also on bottom up confirguatioons.  When I do kilns for clinets I NEVER deliberately use that configuration.

 

best,

 

.........................john


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#27 Mart

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Posted 25 September 2013 - 04:40 AM

neilestrick wrote: "don't particularly like having to lay on the floor to adjust my burners"
Here is picture for you, on our web site: "Holy moment" http://www.oostuudio...08/IMG_7758.jpg (while my studiomate was studying in Helsiki) :)
I have crawled few circles around our gas kiln so I have to agree, it is not the most comfortable location but, it's something you do not have to do too often.

So, bag wall it is :)

All she has to do now, is come up with a design not to lose too many stetson hats worth of valuable kiln space.

#28 TJR

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Posted 25 September 2013 - 07:44 AM

neilestrick wrote: "don't particularly like having to lay on the floor to adjust my burners"
Here is picture for you, on our web site: "Holy moment" http://www.oostuudio...08/IMG_7758.jpg (while my studiomate was studying in Helsiki) :)
I have crawled few circles around our gas kiln so I have to agree, it is not the most comfortable location but, it's something you do not have to do too often.

So, bag wall it is :)

All she has to do now, is come up with a design not to lose too many stetson hats worth of valuable kiln space.

Hilarious! A good laugh first thing in the morning when I am on my way to deal with those lazy Grade twelvers. That doesn',t even look posed.



#29 TJR

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Posted 25 September 2013 - 07:48 AM

Why do you like to spend energy (BTU, kWh) for heating up that bag-wall? :)

Will this work, if you send flames straight up?

This is a 3 min quick sketch, I hope it makes sense. What do you guys think, will this work? (I forgot the salt/soda opening)

 

attachicon.gifCD_kiln.jpg

 

Now you will have a bit less than 29 stetson hats of space but still more, than on the drawing you had. I am not telling, your idea is wrong but it looks like something you want to use when building a wood fired kiln.

Every brick you place inside the kiln, needs to be heated up. There is no way around it. 

 

NB! Kristin, pay really close attention to page 21 in The Art of Firing ;)

I agree with Neil on this one. We usually do agree. Not a fan of burners coming in from underneath the kiln.

1.Take a look at the sketch. Place the burner in through the wall horizontally.

2.To the left of the burner place three bricks along the floor.Otherwise, your flame will move under the shelves and out of the kiln. You will have a hot floor and a colder top.

Just sayin,

TJR.



#30 neilestrick

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Posted 25 September 2013 - 09:22 AM

neilestrick wrote: "don't particularly like having to lay on the floor to adjust my burners"
Here is picture for you, on our web site: "Holy moment" http://www.oostuudio...08/IMG_7758.jpg (while my studiomate was studying in Helsiki) :)
I have crawled few circles around our gas kiln so I have to agree, it is not the most comfortable location but, it's something you do not have to do too often.

So, bag wall it is :)

All she has to do now, is come up with a design not to lose too many stetson hats worth of valuable kiln space.

 

That is HILARIOUS!


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#31 Kristin_Gail

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Posted 25 September 2013 - 08:02 PM

Oh!  I feel so much better - as though I've actually learned a bit in the past few months of kiln-construction-information-cramming.  Because my reaction to your suggestion, Mart, was, "But don't I need a bag wall to even out temp?  If I were the flame in your drawing, I would just come in, turn left, and go straight out the flue - who needs to go all the way to the top?" and "I want to put wood / charcoal in this thing - I can't have the burners coming out holes in the bottom, getting all clogged up.  Also, I'm going to have a hard enough time securing the things horizontally sans welder; I have no idea how I'd stand them upright."

 

I'm glad to see the bag wall only need be one brick high.  And here I was going to go 13" high.

 

Another question:

 

...

Just allow plenty of room around and combustable roofing and use metal falshing as you stack will be hot.-You can use hard or soft brick up to the roof -then hard brick in the weather or a stainless steel salvage pipe??

...

 

Is there a magic height at which I can switch to stainless steel pipe?  (As I'm hoping it's less expensive than Canadian-price brick.)


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#32 Mark C.

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Posted 26 September 2013 - 10:11 AM

Once you get above 5-7 feet you can switch to cheaper fireplace bricks (these are rated lower temp than a high fire brick) .

For me I put salvaged stainless steel pipe from a pulp mill on top of my 8 feet of brick.

Mark


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#33 Stephen

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Posted 26 September 2013 - 10:57 AM

Hi Kristin,

There's a company here in WA that is selling firebrick on ebay by the pallet, may be worth taking a look:

http://www.ebay.com/...=item4d092956d9

#34 Kristin_Gail

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Posted 26 September 2013 - 01:01 PM

Hi Stephen - I'm East of Maine!  That, um, is a looooong way away from Washington.  Unfortunately.



#35 Biglou13

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Posted 26 September 2013 - 07:37 PM

Sometimes you can find soft brick for free.... Chat with local kiln repair guy. Guts from octagon kilns. Sure not as good as hard bricks but the cost is right.
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#36 Mark C.

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Posted 26 September 2013 - 08:41 PM

BigLou 

Shes in either Nova Scotia or Iceland either way there is no local kiln repair guy-No local kiln anything around these parts as well.

Its a good idea if you live near lots of population as thats the onlyway you will have a kiln repair guy.

Free brick are also found at old mill sites-lumber mills (kiln dried wood)-pulp mills-some industrial sites as well.Or at least thats where I have in my younger days found them.

Mark


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#37 Mart

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Posted 27 September 2013 - 02:49 AM

I must have missed something here. :)
Why are you building a brick chimney for your gas kiln?

This is how it's usually built.
Attached File  gas_kiln_ch01.jpg   19.01KB   2 downloads

Sheet metal pipe (duct) is the one that exits the building and if this kin is outdoor, in the open, you do not even need that.
Chimney is to generate draft. You do not need draft like you do in a wood fired kiln. Only draft you need, is the one in that ventilation duct. Make sure you have a dampener there too, if it starts sucking that air out too fast ;)

Here is another example.
Attached File  kiln_picture.jpg   30.26KB   1 downloads

Burning gas, you shoot in to your kiln, will generate pressure inside the kiln and it starts to search its way out. When it finds the exit, it pushes out.

 

If I were the flame in your drawing, I would just come in, turn left, and go straight out the flue - who needs to go all the way to the top?"


Actually no. The speed at which the flame (burning gases) exit the burner and enter the kiln, will take them all the way up and go from there, searching for exit.
While your burners are going, there will be higher pressure in your kiln. You do not need traditional draft like you do for wood fired kilns - get air in and gasses out.

If you had a "passive" flame like candle or wood in a kiln - you need a chimney to generate draft or your fire will run out of air and die.

If you have a gas burner, that sucks in its own air (primary and secondary), you need an exit flue for the gases or the backpressure will rise too high and you will have a problem burning that gas and flames will try to exit from burner ports.

If you are planning to throw charcoal in to the kiln, just keep the burners going and they will take care of the gases and air. (I have actually never attempted this so do not take my word for it)

#38 neilestrick

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Posted 27 September 2013 - 08:24 AM

You do not need a tall chimney if you are using power burners. But for Venturi burners like she is using you will need the chimney height to create draw to bring in secondary air.


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#39 oldlady

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Posted 27 September 2013 - 09:36 AM

mart, love the photo.  i realize that people put "gods" on their kilns, but worshipping them the way you guys are seems a little much! :D


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#40 Mart

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Posted 27 September 2013 - 11:18 AM

mart, love the photo.  i realize that people put "gods" on their kilns, but worshipping them the way you guys are seems a little much! :D


:)

You do not need a tall chimney if you are using power burners. But for Venturi burners like she is using you will need the chimney height to create draw to bring in secondary air.


(http://www.wardburner.com/draft.html)
I guess in this case, she needs 41.5+5+5=51.5 51.5/3=17.16 and 3*30=90 + 17.16 = 107.16" tall chimney. huh... over 2.7 meters! That sucks...





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