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RobS

Insulating Kiln Wall/floor Interface

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Hi all,

 

I've an old Reward 822 (8 sided, 18" dia x 22" deep) kiln that I have resurrected.  It was a Craigslist find for fifty bucks (yay).  I have rewired and installed new elements, added a PID controller and generally updated it as best I can.  

 

My issue now is the bottom row of brick where it meets the kiln floor.   At some point in this poor thing's past I think it was moved with it's bottom removed as most of the bricks on the bottom row have the element groove sections broken off with some damage to the bottoms of the bricks as well.  When installing new elements, I set the bottom element on pieces of firebrick and pinned what I had to so the element would not touch the floor.  When the kiln is firing, there is a visible gap between the bottom of the wall and the floor.  I know the best solution is locate 8 replacement bricks, tear it apart and replace them all, but after the elements and controller another $100+ on bricks is not really in the budget.  Can I use some insulation to fill the gaps and stop the heat loss?  I was thinking about 1" strips of blanket or something similar as I'd like it not permanent.

 

Any advice is appreciated.

 

Thanks,

 

Rob

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I had a former student working at a local refractory company. He would give me end scraps of kaowool. That would be enough for your project. Call up some local companies that install fireplaces and see if they have some small pieces of ceramic fire you could use.

 

Marcia

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Guest JBaymore

When you compress the air spaces from the fiber. it loses insulating value. Don't pack it down.

 

Research the MSDS and health information (particularly from the European Union) on ceramic fiber (known in the industry as "Refractory Ceramic Fiber" or "RCF").

 

Look up the new "Isofrax" variety.

 

best,

 

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

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Thank you all for the advice.  I forgot to mention that I'm firing to cone 6 or thereabouts.  

 

So it is okay to put the fiber in direct contact with the elements?  If that is the case, Marcia has a great idea about seeing if I can get some scraps or small cutoffs.  Worst case is I buy a square foot or two online and have extra.

 

Thanks for the warning John.  I am aware of the hazards of the airborne fibers and will use a respirator and work outside when cutting.  The good thing is once this is put in place there should be no need to touch it until I'm ready for new elements.

 

Rob

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I used 2300 fiber soaked in ITC 100 and stuffed it into cracks in kilns at UH Manoa when I was teaching there. There were some pretty rough kilns there and they needed some TLC.It worked well and those kilns went to 9-10 regularly.

 

Marcia

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I lucked out today.  I called around the area to fireplace, heating and plumbing distributors and one of them had a damaged chunk of kaowool they were looking to get rid of on the cheap.  It is the 2300' 1/2" blanket.  It intended use was to line a large boiler combustion chamber bottom, but it was unwrapped and torn up on the edges.  It's 3+ square feet and he charged me $10.  Thanks Marcia!

 

So tomorrow I pull the pins on the bottom element, remove it and line the bottom corner and damaged areas with the blanket pieces then reinstall the element on top of the blanket.  It will be interesting to see how much more evenly my kiln heats with these leaks sealed.  It is usually a whole cone cooler on the bottom as on top depending on how I load it.  I have been loading less dense and taller wares on the bottom to help with the heating evenness.  

 

As for the ITC-100, it looks like an excellent product although too pricey for me right now.  I will buy some when I can and at least coat the bottom parts of the kiln.  Interesting stuff that you can spray right on elements and bricks.  I've done a bit of poking around on the internet and some people are using a 70/30 blend of zircopax and kaolin as a workable substitute.  I may mix a little up and brush it on some of the extra wool I'll have and fire it a few times to see what happens.

 

Thanks again for all the valuable advice.

 

Rob

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That mixture I think may put a thick crusty coat on the fiber-I suggest testing it a spare pice 1st.

I'll try to get around to posting a better coating formal-I would just stick to not coating your scraps at this point.You could add some rigidizer

Mark

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Mark,

 

Thanks for your thoughts.  Yes, I was planning on testing a mix or two on some of the left over wool pieces and firing them whenever I fire the kiln.  I can isolate the chunks and keep an eye on them from firing to firing looking for cracking, peeling, flaking or any other undesirable behavior.  

 

I agree with you that without a proven coating (ITC-100) I would be far better off just applying the wool to the cracks and crevices in the bottom wall of the kiln and reinstalling the element on top of the fiber.

 

Thanks again and I will have a look at your coating post.  

 

Rob

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Good morning all.
 
While I have my morning coffee, I thought I'd post an update on my project.  I cut the kaowool into about 2" strips, folded them in half and gently stuffed them around the base of the kiln where it meets the wall.  I installed them with the "V" of the fold pointing towards the outside of the kiln in hopes that the wool will act as a pseudo element groove.  Element was reinstalled on top of blanket.  While I had the kiln in service mode, I figured I'd add a vent too.  Docweathers posed a home made kiln vent in another post and I happened to have all the relevant pieces save the fan.  So for $23 and a wait of 2 days from Amazon, I had a fan and nice kiln vent.
 
I ran a bisque Friday and was pleasantly surprised at my results.  Pre-fix, this kiln would consistently fire at least a cone hotter on top.  Post fix, the kiln fires quite evenly and I have zero smell due to the vent.  I spent yesterday glazing said bisque and a glaze load is now cooling.  We'll see tonight sometime.....
 
Attached pics show the most recent firing's cone packs:  top, middle, bottom, cones 05, 04, 03.  Yes, I was out of large 05 cones and the small ones look funny, but they're there just as a sanity check anyways.  The other pic is the bottom most row of elements after the repairs and the one bisque firing.  The shelf in the picture is sitting on 1" posts on the floor and stays there as extra insulation.

 

Thanks again for the advice and encouragement.

 

Rob.

 

BTW, why is it that the glaze bucket you kick over is the one with 2+ gallons of 15% RIO glaze?  What a mess, at least I have concrete floors.

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The other option to make the kiln joints fit tighter is to work a piece of stiff sandpaper into the joint and sand down the high spots on the bricks. I had some 100 grit sandpaper  from a hardwood floor sander that worked great for mine when I replaced some bricks.

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