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Real-Time Kiln Advice (Kiln Curently Firing)


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#41 TJR

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Posted 20 May 2014 - 03:47 PM

Your top shelf post in the middle should be placed above another post. You have no support there.That shelf could crack and fail.

Tom.



#42 neilestrick

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Posted 20 May 2014 - 03:56 PM

 Looks too crowded for combustion.

 

I mostly disagree. I've fired little kilns with tight fireboxes like this before without any trouble. I wouldn't change anything there yet.


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#43 JBaymore

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Posted 20 May 2014 - 04:08 PM

 

Looks too crowded for combustion.

 

I mostly disagree. I've fired little kilns with tight fireboxes like this before

 

 

Looks too crowded for combustion.

 

I mostly disagree. I've fired little kilns with tight fireboxes like this before without any trouble. I wouldn't change anything there yet.

 

 

without any trouble. I wouldn't change anything there yet.

 

 

Ditto.

 

best,

 

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


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Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

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#44 Kristin_Gail

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Posted 20 May 2014 - 05:24 PM

Replace the soft brick bag wall with hardbrick. You want six inches from the kiln wall on the left to the bag wall. The target bricks may be in the way. Do they prevent the flames from going under the work?
TJR. Looks too crowded for combustion.

TJR - in the photo you're referring to (the last one posted), the burner ports are at the bottom. The holes you see on the right/left of the target bricks are not for burners. They're for wood (which I don't plan to use).

There are nine (9) inches between the kiln wall at the bottom (burner ports) to the bag wall.

#45 Kristin_Gail

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Posted 20 May 2014 - 05:31 PM

Tomorrow we hope to find a way to cut the bricks for the bag wall.

Then I'm thinking of doing a quick video tour of the whole kiln, just to make sure I haven't thoroughly confused y'all with the photos.

#46 Kristin_Gail

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Posted 20 May 2014 - 07:21 PM

I'm beginning to get the idea that perhaps I should ask for help *before* I build something, instead of asking for help when the something doesn't work.  So.  Here's how I plan to build the new hard brick bag wall.  

 

bag_wall_plan.jpg

 

To the right of each layer are numbers I was shooting for - the top number is the total number of inches of space between bricks across the layer.  The bottom layer is the total number of brick inches across the layer.  

 

The top layer is off by 1/2", but the cuts won't be perfect.  I can choose the smaller 4.5" bricks for that layer.



#47 Kristin_Gail

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Posted 20 May 2014 - 07:23 PM

No specific inch recommendations on how far the target brick (on a 45) should be set inside from the burners?



#48 neilestrick

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Posted 20 May 2014 - 09:07 PM

For the target bricks I would put a brick standing straight up with the narrow side facing the burner ports. The idea is that the flame hits the brick and splatters out all over. If you set it in at an angle it will just ramp flame upward. It may be sticking into the firebox a bit far that way, so if possible cut it lengthwise, or set it into the bag wall so it doesn't stick out quite so far.

 

You can cut those bricks with a masonry blade on a circular saw. The dust will do bad things to your saw so don't use a good one. Wear a mask and eye protection.

 

I think you're over thinking the bag wall. You are not going to want to cut that many bricks. It does not have to be perfectly symmetrical and even. A few gaps here and there are fine and will do the job. I would keep the bottom layer gap free.


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#49 Mark C.

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Posted 20 May 2014 - 09:25 PM

I agree on asking before the fix is needed-its a lot easier on you and your gas bill.

 

On that thought-Tom brings up a Great point thats that stilts/Posts need to be above one another

Thats a basic practice in all posting in all kilns at all temps and your top shelve shows not much line up with stilts underneath it?-so in the future put the stilts one on top of each other with the shelve in between-otherwise you are just asking for problems-cracks or failures on shelves

 

As far as a bag wall I'd just cut some bricks in 1/2 with a wet or dry diamond saw-you can cave man this with a brick chisel as well but the breaks are rough which really will not matter as a bag wall.Just use full and 1/2 bricks and ,maybe a few 1/3 bricks

I think you are over thinking all the dimensions-if you have a brick saw you cuold cut a few bricks into 1/3s to mix it up.

Cutting hard brick is a far cry from soft brick cutting

Cut only what you need per layer-lay it out with my above options and cut less.

Mark


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#50 Kristin_Gail

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Posted 21 May 2014 - 06:39 AM

I didn't think much with the first one. I just cut some bricks and set them in there.

My husband works in the landscape industry - he was just going to take the bricks with him to a job site today and cut them there; figured it would be quicker than other options. Because he'd be away from the kiln, I thought I'd see how things would stack up first, as I couldn't make any adjustments while building.

Because I did have comments about tightening up the bag wall, evening out spaces, back on page 2 - so I thought it better to show y'all first. Someone also mentioned (John?) having 1" gaps in the bag wall on the bottom layer, behind the target bricks. But now I'm reading different?

Marc Ward had mentioned having 10% of the first layer be gaps, 20% of the second layer, 30% of the third. What I have now is pretty much what's in the drawing, which is certainly not following these guidelines.

Oh yes, and on the shelves - I ran out of the rectangle shelves that stack nicely atop one another and had to use half-rounds on the top. I can't fix that, but I can try harder to get two of the three supports to line up.

#51 JBaymore

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Posted 21 May 2014 - 10:13 AM

While all those evenly spaced out holes are probably a good idea once you get location and sizes right... they are liekly also overkill and more complex than you need in a kiln this small.  (I just designed the checker-wall at the back end -before the suetema - of a new anagama I'm designing we'll build this summer.  It's a big wall full of small holes for a large cross draft kiln that resembles what you are trying to do there with your bag wall.)  If it is easy to do, then do it.  But otherwise........ a simpler combination of full and halfs can likey work almost as well.

 

In the bottom couple of layers, do not have a hole line up directly with the axis of the burner flame coming out of the burner.  Other than that, with crossdraft circulation I think you need SOME opening down there as well ... not much ... but some.

 

For me, I want the flame to "break" across the angled face of the target bricks ... not splatter by hitting them flat on.  (Look up the term "flame quenching".)  After the target splits the flame, it then will hit the bag wall "flat on".  When I say "angled" I do not mean tipping the bricks upward..... I mean setting them vertically so a corner edge is right on the axis of the burner flame.  To have this a very even "split", a soap is best. 

 

Keep the target brick as far as possible from the burner nozzle in that small kiln.  I'd set the back edge of the target bricks right agaions the bag wall in this angled case.

 

The exact spacing of openings and non-openings gets "tuned" over multiple firings based upon results.  Once you have the basic kiln working OK....... change things very slowly to measure how the change affedcts results.  Whenever possible change only one thing at a time per firing.

 

best,

 

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


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#52 Kristin_Gail

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Posted 21 May 2014 - 01:28 PM

Bracing myself for another catch of something ridiculous discovered in the photos, here's the new bag wall and target bricks.

 

new_bag_wall.jpg

 

I didn't have any more regular bricks to use for the target bricks, so we cut up a large flat one we had leftover from the chimney.  They're about 2.5" across and 8" high.

 

target_bricks_01.jpg

 

target_bricks_02.jpg

 

The bag wall is now only about one inch away from the shelves - somehow I moved it back a bit when building.  If there's some sort of formula to decide how far to keep it from the burners, I'd love to use it.  Would be happy to move it forward if necessary.



#53 TJR

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Posted 21 May 2014 - 01:37 PM

I think you can afford to move the bag wall an inch toward the burners. You don't have much space to lift your kiln shelves in and out of there.

Also, your primary air on the burners is still pretty far open. I would crank it down some more.

TJR.



#54 Kristin_Gail

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Posted 21 May 2014 - 01:46 PM

Thanks, TJR.  I'll probably go move it an inch or so.  I've already built it three times today, why not go for four.

 

At the end of the last firing, I couldn't get it to stop reducing.  I played with the damper/primary air endlessly.  Apparently at the very end I had them wide open. 



#55 JBaymore

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Posted 21 May 2014 - 02:02 PM

Was the chimney brick you selected at least HIGH DUTY?  If you used low duty bricks there maybe at the top.... in the firebox like that..... it'll melt a bit. Not a puddle.... but totally bloat and deform.

 

Yes you can move the bag wall away from the shelves.... that would actually be good circulation-wise and also thermally.

 

Do I remember from prior conversations that you are running on LOW PRESSURE gas to that burner manifold setup?   Like 11 inches Water Column or something?  If so... expect the P Air shutters to stay very much open... and still not entrain all that much primary air. Can't remember back that far and no time to look back in the various threads....sorry.

 

best,

 

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


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#56 Kristin_Gail

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Posted 21 May 2014 - 02:46 PM

As I recall, these chimney bricks were super-duty.  I'm trying to find my receipt now.  I was told these bag wall bricks are super-duty, but have no way to verify.

 

And, yes, it's a low-pressure system.



#57 Mark C.

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Posted 21 May 2014 - 03:07 PM

I agree on moving that bag way a bit towards the burners and away from shelves as thats real tight to shelves and leaves a lot of extra cumbustion space not needed (5-6 inches for a kiln this size is plenty)

 

Those target bricks look fine-those are close to a true soap brick which is a brick cut long wise in half (9" long 2 1/2 wide)

Good luck with the fire

Mark


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#58 Kristin_Gail

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Posted 21 May 2014 - 03:14 PM

Thanks, Mark. I had no idea what John meant by a soap brick. It tickles me that I accidentally used (close to) one.

#59 Mark C.

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Posted 21 May 2014 - 03:36 PM

It would be a good thing to read a book on kilns like Olsens kiln building book-in there are all the brick shapes and dimensions

Its what all basic potters should know-it most likley can be had online soomewhere these days.

Knowing what soaps and splits are as well as all the arch and flat brick sizes are will help in the long run. we learned this in school 40years ago and I know them almost by heart

I'm amazed you build your stack without knowing any of this?

Knowledge is power they say.

Mark


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#60 Kristin_Gail

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Posted 21 May 2014 - 03:40 PM

I'm very bad at losing information quickly. I read not all of The Kiln Book, but certainly much of it, and all of The Art of Firing. And this was only a number of months ago. I didn't immediately use what I had learned, so I lost it.




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