Looking For Recipe For Light Weight Kiln Bricks For Electric Kiln

[Guest JBaymore]

With large areas of castable, you need to build in expansion / cracking joints.  Saran Wrap does a gret job of causing the "cracks" to be tapering toward the interior (similar to arch bricks) if you plan correctly.  Plus fired-in-place castable is NOT generally a good choice.... because the hot face side is fired...and the cold face side is not.  Sets up thermal stresses parallell to the hot face surface.... and invites spalling.  Castable shapes should be fired in another kiln whenever possible.

 

best,

 

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

[High Bridge Pottery]

Thanks, I thought there would be expansion problems and firing problems. I just saw a video a while back of a gas conversion that Simon Leech did and got inspired by his lid as it looked like a solid cast.

 

Either building one out of IFB or casting, they both seem to have their downsides.

[potter232]

I have used a padding saw - in the UK that's a cheap narrow tapered saw blade with a detachable wooden handle at one end - and it does a great job with no worry as to spoiling a machine. I used it outside to minimise the dust problem. Thought I would like to try making light weight bricks, but think maybe it's not worth the hassle, except for the interest in making something new - that's what pottery is all about, isn't it?

(Sorry - this is of course for cutting the bricks!)

[Norm Stuart]

If you really want to do an experiment, I'd suggest you cast a brick made of a Phosphate Cement like Kast-O-Lite mixed with Sawdust.

 

Then fire this one brick in a kiln to burn-out the sawdust and fully cure the Phosphate Cement.

 

The resulting product may very well have an insulating value near or superior to IFB, while possibly possessing strength near or superior to that of IFB.

 

I have used a padding saw - in the UK that's a cheap narrow tapered saw blade with a detachable wooden handle at one end - and it does a great job with no worry as to spoiling a machine. I used it outside to minimise the dust problem. Thought I would like to try making light weight bricks, but think maybe it's not worth the hassle, except for the interest in making something new - that's what pottery is all about, isn't it?

(Sorry - this is of course for cutting the bricks!)

[ChenowethArts]

I'd try mixing Wollastonite and Phosphoric Acid and pressing it into a mold with the groove indentation already in the mold.  It becomes hard after 20 minutes or so and cures fully at 550F.   http://cone6pots.ning.com/photo/wollastonite-phosphoric-acid

 

It's generally porous enough to stick kiln pins into and stable up to 3,040 F.   But you can mix in pumice stone or soft fire brick ground up to end up with something a little less strong and easier to stick pins into.  These are slightly different starting ingredients to kiln repair cement you'd buy from your kiln manufacturer.

 

Someone mentioned a calcium-phosphate or magnesium-phosphate cement at Home Depot that may be less expensive.  I think most are  two part cements mixing Ammonium Phosphate with Magnesium Oxide or Calcium something.  But that's what you're looking for, a phosphate cement.

 

Norm, I am getting closer to converting the pieces/parts from two old electric kilns into a propane, updraft gas kiln... very similar to this project: http://codyopottery.blogspot.com/2009/10/electric-to-gas-conversion-birth-of-my.html   After looking at the hole in this guy's kiln where the propane is introduced, I'm considering molding a pipe that would slide through the rectangular cut in the side of the kiln, basically rectangular profile pipe on the outside but round in the center where the gas flame would pass through.  Would this Wollanstonite-Phosphoric Acid mixture work for this? If so, what sort of mold release would you recommend?

 

Thanks,

Paul

[neilestrick]

 

I'd try mixing Wollastonite and Phosphoric Acid and pressing it into a mold with the groove indentation already in the mold.  It becomes hard after 20 minutes or so and cures fully at 550F.   http://cone6pots.ning.com/photo/wollastonite-phosphoric-acid

 

It's generally porous enough to stick kiln pins into and stable up to 3,040 F.   But you can mix in pumice stone or soft fire brick ground up to end up with something a little less strong and easier to stick pins into.  These are slightly different starting ingredients to kiln repair cement you'd buy from your kiln manufacturer.

 

Someone mentioned a calcium-phosphate or magnesium-phosphate cement at Home Depot that may be less expensive.  I think most are  two part cements mixing Ammonium Phosphate with Magnesium Oxide or Calcium something.  But that's what you're looking for, a phosphate cement.

 

Norm, I am getting closer to converting the pieces/parts from two old electric kilns into a propane, updraft gas kiln... very similar to this project: http://codyopottery.blogspot.com/2009/10/electric-to-gas-conversion-birth-of-my.html   After looking at the hole in this guy's kiln where the propane is introduced, I'm considering molding a pipe that would slide through the rectangular cut in the side of the kiln, basically rectangular profile pipe on the outside but round in the center where the gas flame would pass through.  Would this Wollanstonite-Phosphoric Acid mixture work for this? If so, what sort of mold release would you recommend?

 

Thanks,

Paul

 

 

Burner ports are a great place for castable.

[Guest JBaymore]

For high fire work I typically use a high alumina castable for burner blocks.  Fully fired in another kiln before installation.

 

Top right side of page......... http://www.johnbaymore.com/page31.html

 

best,

 

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

[Norm Stuart]

Wollastonite mixed with phosphoric acid sticks to brick or other things early in the mixing stage.

 

After it has fully reacted into the pH neutral moldable putty, after about 10 minutes of mixing occasionally, it won't stick to anything - not even other pieces wollastonite/phosphate cement.

 

It's amazingly low-expansion. I've applied and fired ^6 glazes, even low-expansion lithium glazes, on this when it's hard - perhaps use it as a sculpting material.  But when you take the piece out of the kiln, just brush it off or tap it lightly and all the glaze falls off the wollastonite phosphate

 

I'd try mixing Wollastonite and Phosphoric Acid and pressing it into a mold with the groove indentation already in the mold.  It becomes hard after 20 minutes or so and cures fully at 550F.   http://cone6pots.ning.com/photo/wollastonite-phosphoric-acid

 

It's generally porous enough to stick kiln pins into and stable up to 3,040 F.   But you can mix in pumice stone or soft fire brick ground up to end up with something a little less strong and easier to stick pins into.  These are slightly different starting ingredients to kiln repair cement you'd buy from your kiln manufacturer.

 

Someone mentioned a calcium-phosphate or magnesium-phosphate cement at Home Depot that may be less expensive.  I think most are  two part cements mixing Ammonium Phosphate with Magnesium Oxide or Calcium something.  But that's what you're looking for, a phosphate cement.

 

Norm, I am getting closer to converting the pieces/parts from two old electric kilns into a propane, updraft gas kiln... very similar to this project: http://codyopottery.blogspot.com/2009/10/electric-to-gas-conversion-birth-of-my.html   After looking at the hole in this guy's kiln where the propane is introduced, I'm considering molding a pipe that would slide through the rectangular cut in the side of the kiln, basically rectangular profile pipe on the outside but round in the center where the gas flame would pass through.  Would this Wollanstonite-Phosphoric Acid mixture work for this? If so, what sort of mold release would you recommend?

Thanks,

Paul

 

[Mart]

Wollastonite mixed with phosphoric acid sticks to brick or other things early in the mixing stage.

 

After it has fully reacted into the pH neutral moldable putty, after about 10 minutes of mixing occasionally, it won't stick to anything - not even other pieces wollastonite/phosphate cement.

 

It's amazingly low-expansion. I've applied and fired ^6 glazes, even low-expansion lithium glazes, on this when it's hard - perhaps use it as a sculpting material.  But when you take the piece out of the kiln, just brush it off or tap it lightly and all the glaze falls off the wollastonite phosphate

So basically this stuff can be used to make supporting firing moulds for thin objects that can fall flat. Glass and thin porcelain come to mind.

[Norm Stuart]

The Wollastonite Phosphate castable is an absolutely ideal material for making bowl setters.

 

You'll quickly become familiar with how long the reaction process is.  This reaction time can be prolonged by adding the portion of acid to additional water (always pour the acid into water, never pour water into acid as acids release heat when diluted and can steam/splatter the acid out of the container of acid).

 

The combination of Wollastonite bubbles and rises in temperature as you mix it. Using cold water will also prolong the reaction time.

 

Initially the combination is a sticky cement which easily adheres to many types of material.  After the bubbling stops, the material becomes a pH neutral putty which can be molded to any shape without adhering to the mold.  With very little added water, the material hardens within five minutes.  If you added additional water, the hardening time will take longer.  As the Wollastonite Phosphate hardens, if needed, the exterior can be tooled to a very smooth surface.

 

The Wollastonite Phosphate achieves full strength after being fired to 550 F (288 C).

 

 

Wollastonite mixed with phosphoric acid sticks to brick or other things early in the mixing stage.
 
After it has fully reacted into the pH neutral moldable putty, after about 10 minutes of mixing occasionally, it won't stick to anything - not even other pieces wollastonite/phosphate cement.
 
It's amazingly low-expansion. I've applied and fired ^6 glazes, even low-expansion lithium glazes, on this when it's hard - perhaps use it as a sculpting material.  But when you take the piece out of the kiln, just brush it off or tap it lightly and all the glaze falls off the wollastonite phosphate

So basically this stuff can be used to make supporting firing moulds for thin objects that can fall flat. Glass and thin porcelain come to mind.

 

[Bob Coyle]

....But then there is shipping which most of the time doubles the price on things like bricks and mortar.

[High Bridge Pottery]

Found this pdf - The Self-Reliant Potter: Refractories and Kilns by Henrik Norsker

 

Has some good info, just working my way through reading it now.

 

https://drive.google.com/file/d/0ByISKVubkZcXbEJaWllObmJXRTQ/edit?usp=sharing

 

A few recipes I have found too:

https://docs.google.com/document/d/1jPhBlTCVd3B6V9PdIkFW8A-npnOGui-evnfmJzIdUEE/edit?usp=sharing

[High Bridge Pottery]

I have a question about kiln bricks. Is there a right way round to use them?

 

Say I have the standard 9" by 4.5" by 3" is it better to use the 4.5" as the width of the kiln or the 3"? If I was going to put elements into bricks I would have thought the 4.5" side would be better for that but then is 3" enough insulation.

 

I am confused