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jgestner 05-10-2011 10:47 AM

Castable questions
Hi Gang
I am just starting to look into the idea of buying/building an outdoor oven.
I have a whole list of questions and even a few likely off the wall ideas. Please let me boor you with just a few in this post.
1. I am in Wisconsin and wonder if it is possible to use an oven in the winter with -10F temps as often as 40F for 6 months of the year.
2. I have a crazy idea to form an oven from a casting of the inside of my wheelbarrow. It seems about the right size and shape for at least 1 16" pizza and a bit of a fire. A separate brick opening might be nice looking and functional if a chimney is needed, and a door seems preferred also. Can it be done? I haven't ever touched refractible cement mixtures, but have done pottery firing as an art teacher many times.

For any information any of you might be willing to share.

Merrill, WI:confused:

david s 05-10-2011 11:58 PM

Re: Castable questions
I think your idea has merit. be sure to paint the barrow with a release agent. I use motor oil, kerosene 50/50. You could cast in the door ensuring the 63% ratio of door height to internal oven height. The barrow form will give you a good release. I am also a pottery art teacher and much of the information and learning crosses over. Presume you have a fair amount of experience making castings. Suggest you make the walls 2" thick (check with a marked satay stick) and add stainless steel needles (at least 2% by weight) to the mix. don't mix more than one 50lb bag at a time it goes off really fast. Make the flue gallery separately to take the flue pipe.

brickie in oz 05-11-2011 12:27 AM

Re: Castable questions
Thinking outside the square, cool. :cool:

We need pics of the progress.

jgestner 05-27-2011 01:54 PM

Re: Castable questions
Hi Gang
I am still in research phase, but have made some progress.

I am looking at a product from Empire Refractories for casting my own oven shell. It's called KS-4V Plus and they have it for $41.47 per 55 LB bag. I believe it is an ANH/Harbison Walker product and from the MSDS here is the main ingredients...
Chemical characterization
Description: Mixture of the substances listed below with nonhazardous additions.
1302-93-8 alumina silicate 30-60%
14464-46-1 crystalline silica (cristobalite) 20-30%
1344-28-1 non-fibrous alumina 10-20%
12042-68-1 calcium aluminate 3.3/2A, 3.8/3 10-20%
14808-60-7 crystalline silica (quartz) 0.5-0.9%
organic fibers 0.1-0.5%

Two different refractory supply places that I talked to thought this would be an appropriate material to use. I was wondering if anyone out there has used this formula refractory cement for their WFO builds.

Thanks for any advise.
John in Merrill

jgestner 05-27-2011 02:16 PM

Re: Castable questions
2 Attachment(s)
Oh David
Should I take the meat off the satay stick before or after I measure?

And how about using this composite lawn edging for stackable side forms and arched entrance?

John in Merrill

david s 05-28-2011 02:49 AM

Re: Castable questions

Originally Posted by jgestner (Post 113852)
Oh David
Should I take the meat off the satay stick before or after I measure?

And how about using this composite lawn edging for stackable side forms and arched entrance?

John in Merrill

1. Always eat first, accompanied with alcohol.
2. I like the composite lawn edging idea. These sorts of oily plastics resist things sticking to them, so I think it will be a good material, but only for straight walls, you'll need something else for the compound curves.

jgestner 06-03-2011 09:13 AM

Re: Castable questions
Hi Gang
I have purchased some materials to start experimenting with cast WFO techniques.
I have a full bag of Vesuvius dense refractory cement, ($25.00) that claims to be 50% ALumina/ Al2O3 and has a temp capability to 2900F. The full data sheet is here Technical Specification Datasheet Level 3
The oven guy that sold me that also sold me 1/2 bag of Mt. Savage Insulating Refractory cement for $10.00. I believe it's one of these, Insulating Castables but haven't had enough time to look too hard at the bag yet.
I hope to use the composite lawn edging like this as inner and outer forms for side walls and arched oven opening sections.

Haven't had time yet to start experimenting, but if any of you see some significant problems with these materials, please get back to me.


John in Merrill

azpizzanut 06-03-2011 09:41 AM

Re: Castable questions
Hello jgestner,

I'm sure you've given a lot of thought to your design and I wish you the best of luck. One thing I'd like to recommend is that you do your best to calculate the amount of refractory concrete you will need. I did some casting lately and ran short. Lucky for me that I was still able to use the casting for its intended purpose.

A vibratory sander held next to the form will help remove air bubbles and voids. I used a hammer drill with a bolt in the chuck to the same effect on 2" x 4" forms for concrete slabs.

You might consider either vermicrete insulation or ceramic fiber blanket on the outside of your oven. Insulating castable refractory is fine too, except it gets expensive. (I used a product called Kaolite). It also adds to the moisture "load" of the oven, as does vermicrete. Just more moisture to drive off with curing fires.

It is easy to post photos of your progress. I'd like to see how your project develops.


david s 06-03-2011 01:25 PM

Re: Castable questions
Your materials sound ok. Don't forget to use some release agent. Don't mix up too much at a time. Use stainless steel fibres (2% by weight). The stuff is quite temp. dependant, add chilled water if it's hot weather and it doesn't need to be cured for a week, just cover it for 24 hrs and you can remove it from the mould and it's ready.Wash out your barrow or mixer before mixing more material to avoid accelerating the new batch going off.

david s 06-03-2011 03:08 PM

Re: Castable questions
Hey John,
Are you still intending to use the wheelbarrow as a mould? I really like this idea- you could be starting a revolution. You will need to form a door and make sure it is around 63% of the height of the oven interior. Once you have created the casting you can build a form in front of the door. Damp sand is the easiest, then cast over the sand with the castable to form your flue gallery (1" thick should be sufficient for this). For your barrow dome I think a 5" flue should be sufficient.

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