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Old 01-24-2014, 02:23 PM
Peasant
 
Join Date: Jan 2014
Location: MA, US
Posts: 41
Default A castable Barrel Oven with Refractory or Homebrew mix

Hello to all alternative oven makers,

I have read quite a few threads on this forum and will continue to do so as I continue in learning more about oven building, pizza making and the dreaded bread baking.

After reading various threads, I have decided to make a castable barrel oven.
I have always seemed to be drawn to linear shapes and the barrel design is calling me out and of course based on my skill sets, I will be far more effective with making forms for the barrel method in creating a functional oven.

Because of budget crunch, I have yet to decide on whether to purchase refractory cement (going back and forth on purchasing some 1-4 years old bags of castable cement from a distributor) or go the way of the homebrew:

3 questions (with add-on's) to those who have been there:


1) Homebrew: I have read of the famous 3:1:1:1 and some have suggested replacing portand with calcium aluminate and/or replacing the fireclay with grog and so on.

I.Current thoughts on the “right” homebrew mix
II.Is the mix by weight or volume

2) What is the ideal dimensions for an effective oven (originally I was going to make a 36” igloo)
I.Hearth width and length
II.Wall height
III.Back wall height and whether to be rounded or squared off
IV.Center of Dome height

3)Insulation: Because of cost restrain, I cannot budget for dreamy ceramic boards (way too expensive in New England)
I thought of a cost effective solution by doubling down in combining an effective insulator (used under a concrete slab) for a heated floor to prevent the heat from seeping past the slab) and the recommended brick way of insulating (vermiculite).
All material added on top of the support slab.


I have more questions, but hopefully you can chime in with your thoughts on these.

Best Regards,

Sandro
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Old 01-24-2014, 03:05 PM
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Default Re: A castable Barrel Oven with Refractory or Homebrew mix

The home brew mix is by volume not weight.
Do not replace the Portland cement with calcium aluminate cement in the home brew mix. The lime in the mix acts as an accelerant when mixed with calcium aluminate cement and results in a mix that will go off faster than you can place it. You could eliminate the lime, but then you'll probably need to increase the calcium aluminate content which will make the mix a lot more expensive.

The clay content in the home brew is important in making the mix workable. If you replace it with grog (fired, crushed clay) the mix will lose this workability somewhat.
Also remember that the proprietary castable mixes usually contain fibres that burn out at low temp leaving a network of minute pipes for water vapour to escape through. If designing your own mix it is advisable to add polypropylene fibres.

Vermicrete is a much cheaper alternative to calcium silicate insulating board, but it needs to have the water removed before it will insulate properly. I think it is better to dry it out as much as possible before building over it and locking the water in. With the cal sil board you don't have this problem.Whatever insulation you use it is best to place it under the floor bricks not under the concrete slab.

Regarding the form of your oven, you can make it any shape you like if you are casting. If you're planning on cooking a lot of bread then a rectangular floor is more suited to loading than a circle. For pizza or roasting I can't see that there'd be much difference. A rectangular form will not heat as evenly as a dome and can have a tendency to having cool spots, certainly in kilns of this configuration anyway, usually in the corners. This could be either a disadvantage or an advantage depending how and what you are cooking.

Last edited by david s; 01-24-2014 at 03:25 PM.
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Old 01-24-2014, 05:16 PM
Peasant
 
Join Date: Jan 2014
Location: MA, US
Posts: 41
Default Re: A castable Barrel Oven with Refractory or Homebrew mix

David,

I appreciate your recommendations. I will keep the Portland in (It is one of two items I have and will have plenty of by end of Feb.)
[I]
"If you replace it with grog (fired, crushed clay) the mix will lose this workability somewhat."
If I use Grog will it make the mix stronger?, to minimize? cracks, If so, I can make small batches and vibrate teh form as I go to insure a densely packed form.

I will add polypropylene fibres and the stainless steel needles to the mix ( I want this baby to last and shine: (my ego is at stake...no...hmmm > bragging rights... Yes! thats it)

Vermiculite: So far I have found a 6 cu. ft. bag for $39 in MA. The nursery is a bit far from me, but so far the best price quoted for the amount.
---Has anyone in MA found a better price. I would prefer to buy in bulk and pick up. - Thanks


"A rectangular form will not heat as evenly as a dome and can have a tendency to having cool spots"

I whole heartily agree with you. One of the first articles I read on this site, was James's article on the effectiveness of rounded ovens (Why Italian Ovens are Round) but desire is one man's weakest points, right alone with lust but I digress.
Thank you, as always
Sandro

PS: I finally saw your oven I have read so much about (it reminded of the little engine that could (outputting 60 + pizza in one outing out of that baby) reading the following thread: http://www.fornobravo.com/forum/43/b...-17285-12.html (Barrel Vault in So. Cal.)

Why is it your oven does not have smoke all over the upper lip? entry when the flue is right on top of the entrance? I have seen many with similar designs with soothe all over the top.

Last edited by Saovicente; 01-24-2014 at 05:29 PM.
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Old 01-24-2014, 05:28 PM
Peasant
 
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Location: MA, US
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Default Re: A castable Barrel Oven with Refractory or Homebrew mix

I forgot to mention: It is #3 vermiculite 6 cu.ft. bag for $39.

Also have anyone out in this small world of ours used the following 2 products:

your thoughts:
Attached Thumbnails
A castable Barrel Oven with Refractory or Homebrew mix-20140115_114424.jpg   A castable Barrel Oven with Refractory or Homebrew mix-20140115_114430.jpg  
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Old 01-24-2014, 05:52 PM
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Default Re: A castable Barrel Oven with Refractory or Homebrew mix

Don't bother with poly fiber in your mix design, they will burn out.
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Old 01-24-2014, 05:57 PM
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Default Re: A castable Barrel Oven with Refractory or Homebrew mix

Type S mortar is 2:1 - Portland/ Lime ratio 1800 psi. It's a building mortar for unit masonry and stonework.
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Old 01-24-2014, 06:21 PM
Peasant
 
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Default Re: A castable Barrel Oven with Refractory or Homebrew mix

Thanks Stonecutter,

I appreciate your input. I have read that one would want type S because it has been hydrated. Do you have any recommendations on a particular lime product to use. In the Eastern part of MA, we have been overrun with the HD, Lowes, that it is becoming harder to find a smaller shop with a "othen than" item.

Best regards,

Sandro
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Old 01-24-2014, 07:03 PM
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Default Re: A castable Barrel Oven with Refractory or Homebrew mix

You want Type S hydrated Lime. Type S mortar is a different animal

Look for a masonry supply yard...guaranteed they will have it, and with all the historic masonry restoration work in area, it should be no problem getting it.
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Old 01-24-2014, 07:09 PM
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Default Re: A castable Barrel Oven with Refractory or Homebrew mix

Here you go, Greater Boston area, they carry Minute Man Lime....I used it many times when I lived in CT.

TLC Supply Cement
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Old 01-24-2014, 07:18 PM
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Default Re: A castable Barrel Oven with Refractory or Homebrew mix

Quote:
Originally Posted by Saovicente View Post
David,

"If you replace it with grog (fired, crushed clay) the mix will lose this workability somewhat."[/I]
If I use Grog will it make the mix stronger?, to minimize? cracks,

PS: I finally saw your oven I have read so much about (it reminded of the little engine that could (outputting 60 + pizza in one outing out of that baby) reading the following thread: http://www.fornobravo.com/forum/43/b...-17285-12.html (Barrel Vault in So. Cal.)

Why is it your oven does not have smoke all over the upper lip? entry when the flue is right on top of the entrance? I have seen many with similar designs with soothe all over the top.
Replacing the clay with grog will do little to add strength. It would be considered a fine aggregate and will act similar to sand. unfired clay particle are much finer and theoretically are also a superfine aggregate so the mix would theoretically be stronger as a variety of aggregate size is stronger than a uniform one.

There are a couple of reasons my oven does not have lots of smoke staining on the front, in spite of the extremely shallow entry (the flue gallery is only 4" deep) 1. adequate flue pipe diameter and 2. a funnel like entry to the flue pipe.
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