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The shelf I am going to use for a damper arrived today. I built the slot for the damper @ 1"x9".       Well that is what Lou said to do!    But there is no 9" shelf so I ordered an 18 x 18 and will cut the shelf down to 9" W.  I have a diamond wheel for the angle grinder, I read in a forum to soak the shelf overnight and then cut it. What say you?  

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Lou is deceased-He was great guy. 

The damper is determined by the chimney size -most use a 12 wide shelve-if yours is smaller (it needs to cover the opening completely when closed )That means overlapping the bricks. You need a slot-most are made with split bricks which are 1 1/4 inch thick x 4.5 x9.This allows a 1 inch thick shelve to slide. You build a slot that the shelve slides on on all three sides .

As to cutting a cordalite shelve use a dry diamond saw blade I a circular saw-you can get them cheap at harbor freight. That way you get clean cuts -wet the shelve or soak as you said. Just make sure its dry before firing it as that will crack it .The grinder will work but  its a sloppy cut at best-more cave man like Fred Flintstone.

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Thanks Mark.

When I first signed on here it was recommended that I read Mel Jacobson's  book. That is where I got the idea for the flat top, seemed easier for me to build.  Lou has the flue dimensions at 4.5 X 7. Then in " The Art of Firing" Lou explains his double venturi system but gives no dimensions on the flue box but does give the exit flue into the stack at 5 5/8 x 5 5/8. From the pictures I believe the flue box dimensions to be 9x5 x10h then it opens to 9x9 for 2 courses in one pic and 3 courses in another pic on the next page. Before it shrinks to  5 5/8x 5 5/x 2.5h and then it empties into the stack which the materials list in Jacobson’s book uses 9in. diameter risers. That is where I got the dimensions for the 9in damper. Lou has it sliding along 3 bricks on edge.

 Will work on the roof today weather permitting.

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I built my salt kiln with Lots double ventrui system.

The damper is between the two Venturi dampers-

My flue exits the kiln into a bit larger chimney chamber and narrows to a 10x10 at damper then goes up about 4 more feet and narrows again at top. Thats about 8 feet of brick then another 10 feet of heavy stainless round about 9 inch diameter.

The dampener in this kiln and all the ones I make are at arm level for easy use.

I have Lots books as well.He has two versions of the same book.

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Postalpotter, I feel your pain, it can be frustrating with so many opinions being tossed into the mix when your trying to get some simple answers.

Been there dine that. Well, I'll toss my thoughts in for what it's worth.

You did the right thing by talking to Ward. The burners are the #1 important thing.

I agree on not needing the fiber blanket. It's nasty stuff but can be ridgidized, but with 9" thick K23 walls you don't need it.

On the bag walls, it you've designed them into the floor on either side of the shelf space, you're good. Staggered bricks, usually 2 rows on their 9" sides should work fin. The idea is to channel the flame and keep the intensity of the flame away form the ware. Target bricks at the end of the channel will help the flame/heat deflect up towards the top where you want it because you have a downdraft set-up. Theory has it the heat will go up and then down towards the flue. I would start your bottom shelves about the height of the bagwalls. You can use posts or bricks on end for this.

My flue is appx. 6" X 9" center bottom at the back. The chimney box is a simple stack of 9" K bricks on their faces making the chimney chamber roghly 4.5" X 9" that raises to the exterior roof of the kiln. From there I have an 8" stovepipe extending about 6 feet.

Reason I offer this is my kiln is of similar dimensions. Interior appx 36" wide X 24" deep and appx 48" high, give or take.

I use standard 12X24 shelves. It has two forced air/propane burners. (2 peep holes in each of the walls and in the door)

Now here's the kicker. my walls are only 4.5" thick with 1" of fiber on the exterior sealed by galvanized sheet. Inside I used that brushable high telmp coating.

Had I not been so A.D.D. at the time of building I would have adjusted the dimensions a bit, probably using more brick as well.

Does it work? Seems to. It can reach cone 10 but it's a bit of a wait. One reason I went to cone 6> glazes.

So yeah, loose the fiber unless it's a pain to remove, at least ridgidize it. You can get liquid sodium silica online or even at some hardware stores fairly cheap.

Big crapper is you having to cut shelves to fit which is a PITA. (Corderite shelves I bet cut easier.)


general dimensions of my kiln:


Edited by Rex Johnson

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On 5/21/2018 at 11:11 AM, postalpotter said:

I am using Mark Ward's duel venturi burners so I am limited in sq. ft.  & BTU's. If I can keep kiln gases and heat from escaping  from the wall is that not a good thing?  I do not know, that is why I ask and then  decide on how to preceded with my next step.  I have yet to add the fiber but?

Forget the fiber. Don't cement your bricks. Stagger yor brick laying so that the inner wall and outer wall overlap. the kiln needs to expand a bit.

 I have a question about peep holes? I will use cone packs on the shelves with the ware but can I have a few packs sitting in a recess in the wall? Could I sent the packs in a 2in. recess? Will that give me a good reading of internal temps? I am thinking of 6 peeps. 2 in the door, 1 on each side of the exit flue above the intake ports and 1 on each wall above the trench? I just want to do a couple of recessed packs not all the peeps but?

Reading top and bottom at least when you start testing is going to be more beneficial as you can keep an eye on the cones > gas/air adjustments/

Was never an art student.

Good ;)




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Thank You Rex!

 Yes, this has been my outlet for a little couch therapy. Not knowing which path to take is a mind killer, slows you down!

  Don't worry I have eliminated the fiber. I was wondering,  every time I look there is more dust from the IFB's on the kiln floor. I am seriously considering  coating the inside of the walls with a high temp coating like ITC 100. Yes or No?

 Today I will put the stack on my kiln. Mark Ward said that I could get away with a chimney that was 8ft. off the floor. With the flue box I will have a chimney of about 10’6”.


 Cut the damper, cut it perfect in one pass, thanks for the advise on the circular saw. Cut it maybe a little to perfect. There is only a small amount of play in the slide. Should it be a bit looser to allow for expansion and contraction?

 Also when I finally put a match to the burners I will do a firing or two empty so I can understand how to work the burners and the air. This will be my first rodeo so I am in no rush to do a load. I understand that time and temperature rise will change when I add mass in the kiln. I was wondering  if you could suggest a cone pack sets that I could watch as I bring the kiln to temp.  So I could watch the temps rise in the kiln and understand what I am looking for. I have no intention of going past ^5 or ^6 for a long time to come. I have a pyrometer with a single probe but shouldn’t I watch a few cone packs also before I do my first bisque. I am not that worried about the dryness of my first bisque, all my pieces have been sitting on the shelves for months, some for more then a year. That is how bad I need a kiln.   Also the thermocouple, should I have a protective sleeve or will just a simple hole in my IFB work fine?   

 Also the addition of an oxygen probe. I found this online,


Should I make this one or does someone have better plans?

 P.S. also

  I am using two Ward MR100’s with the ransome pilots and the BASO any ideas on supports either fix or portable that does not mean stacking and balancing them on cinder blocks?


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It won't hurt to coat the interior but it shouldn't be necessary. Take a good garage vacuum and vacuum it well. That's something I do periodically anyway.

If it's all new K23 brick there shouldn't be that much dust.

You can get by without a thermocouple tube. If I'm correct, they are for protecting the couple from erosion.

I would definitely put cone packs at least in four positions. one high and one low on each side. If you have a peep in the door one or two there too.

Are you stacking the door? If so you can put a couple peeps easily.

If your just going to bisque on the first test I'd use 3 cones, one at before desired temp/desired temp/and higher then desired temp.

On your greenware, it depends on how they've been stored. They can absorb moisture. But a slow candling on the first bisque with peeps, flue open, and door cracked will ensure the moisture is removed. Maybe 2-3 hours on very low burner setting.

If it's just bisqueware that's been sitting, I suppose you could dry them out the same way in the kiln. Make sure they're clean. You might wipe them down before drying.

Glaze doesn't like dust.

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Thanks Rex,


 Well the kiln is basically  finished, I lit the burners this evening and wow what a let down. I was expecting a flamethrower and what I got was a blue flame for about a foot and then just a lazy yellow flame. I know this is a low pressure burner system but? 

 I really have No experience with these things but if there is an interior distance of 27 "for the flame to travel to the far wall plus the 9in. thru the port. The flame exits the port then travels  just about  6 in before it turns up.


 As the heat in my raku kiln builds (weed burner) the flame becomes more intense  and the flame exiting the flue grows in length and color will the same thing happen here?

 As the kiln heats up will the burners become more efficient?

It seams that about 3inWC is the most efficient flame with 9in being my max and with that there is only a small change in flame intensity. 

After all that work building this thing I was expecting something more intense!

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Yes having some play in damper is good as it all expands.

I cannot recall if this in a propane or natural gas  kiln-???????I read back thru a page or two and did not find that info out?

My guess is propane as your pressure is over 1/4 #. I'm not as well vs on propane but newbies usually start with to much gas.

The thermocouple needs a cover to last any length of time in a reduction atmosphere -it will work for awhile uncovered

as to the burners is the kiln empty or full as that makes some difference  to flame paths.To heat a kiln you do NOT NEED A JET ENGINE.

gental flame to start slowing getting bigger

forget about a weed burner-I have one and its for weed not a real kiln.

Remember (Looking forward to the climb, just sorry I choose the steepest route. )

Your words above

mine below

This story reminds me when I decided to go to the moon in my own rocket. I thought I would be easy-but now months later I'm still stuck on earth.


as to the ITC I suggest you forget that at $375 a gallon and if you want a coating your can use the one I posted about for reduction kilns on soft brick.


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19 hours ago, Mark C. said:

This story reminds me when I decided to go to the moon in my own rocket. I thought I would be easy-but now months later I'm still stuck on earth.

Look for my next posting in a few days


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If you ask 5 potters a question, you'll get 20 answers.<- old saying.

I missed this conversation as I have been busy. I built a minnesota flat top many years ago. I had been a sprung arch believer before that and had built catenaries too. The Minnesota flat top started slipping bricks in the top. Before getting worse, I rebuilt it with a sprung arch.  It was a large kiln 60 cu ft. so maybe the flat top wasn't a great application there. And yes, Lou was a great guy. I have his book , the Art of Play as well as his firing book which I got after 30 years of experience firing.

For your stack with venturis, the height depends on your altitude. They are natural draft as compared to forced air which then it doesn't matter on the height. the blowers do the work. I don't know where you are building this. Mark and Neil are good resources as is Magnolia Mud. We all have our favorite way of getting things done.  and they all work. My favorite floor plan for a down draft is burners enter from the back each side of the stack. I love bag walls and put target bricks at the end of the trench, use the bag wall to support the shelves and use the third post in the center front and back in front of the flu but not restricting any flow.  That has been my favorite for 45+ years. I built several this way where I taught at a university for 25 years. I built cross draft catenaries for oil burners made from house hold burners remade for 3 nozzles for adjustable BTU output. Mark Wards Burners are great and he'll make them for your required needs. Good luck with the kiln. Firing your own kiln is a thrill. Then it is confidence. Then it is gratification. Enjoy.


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