#21  
Old 06-19-2012, 11:29 AM
Serf
 
Join Date: Oct 2010
Location: Hampton, Minnesota USA
Posts: 17
Default Re: Oven opening size

Quote:
Originally Posted by Optionparty View Post
http://www.fornobravo.com/forum/3/an...tos-690-2.html (Ancient Roman Oven Photos)

I had a hard time finding them too. (Used Google to search fb site)

Carl
Well meaning workmen, worked on my oven while I was in the USA.
It still works, but it has lost it's beauty. Just brickwork to them.
Sorry

Carl
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  #22  
Old 06-19-2012, 01:48 PM
david s's Avatar
Il Pizzaiolo
 
Join Date: Mar 2007
Location: Townsville, Nth Queensland,Australia
Posts: 4,518
Default Re: Oven opening size

Quote:
Originally Posted by dragonsoup View Post
I disagree with your method for mixing the insulating concrete. The cement and water should be mixed first to form a slurry. Strict attention to the water to cement ratio must paid. Additional water beyond the specified amount will weaken the concrete. Once the slurry is formed add the aggregate. Perlite is a slightly better insulator than vetmiculate so that's what I would use. Both are fine though.

Rent a tumble mixer for this and make your life easier.
Both vermiculite and perlite tend to break down if mixed too much. I've tried using a mixer, but not found it an improvement. The mix sticks to the sides, you can't inspect the mix easily and judge your water addition and you have to scrapeoutworn the sides with your hands anyway. If mixing in a barrow or large bucket you can see the mixing process better and clean up is easier.regarding water content I have tried the "mix a cement slurry first" but have gone back to mixing the vermiculite or perlite with dry cement before adding water.The correct amount of water is critical. If you end up with water pooling at the bottom then you've added too much. It seems to simply wash the cement off the grains and takes the cement with it to the bottom.
I've also found the ratio of 10 parts vermiculite or perlite to 3 parts water is about right for the layer over the dome (use a 5:1 mix for the insulating slab under the floor), but this does vary with the grade of stuff you get. Fine vermiculite for example needs about 4:1
The other thing I discovered was that a 50/50 vermiculite, perlite mix works up to a much more workable mix than either of them alone, have no idea why, but it works well for me.

Last edited by david s; 07-10-2012 at 03:21 PM.
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  #23  
Old 01-19-2013, 10:26 PM
Master Builder
 
Join Date: Jan 2013
Location: Tochigi Prefecture, Japan
Posts: 590
Default Re: Oven opening size

Back to the issue of opening size.
I have a question on actual placement of oven opening in relation to the inside of the oven. The pompeii oven ebook shows the oven opening tangent to the arc of the interior of the oven dome. Is there any critical dimension to worry about? All discussions are about ratio-dome height to opening height-width not important. If a tunnel is present making the oven opening 8" from the point of tangency then a transition made to the vent chamber, will there be a problem with venting of the smoke? Is the landing considered the place between the oven opening and the outer surface of the vent chamber?
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  #24  
Old 01-20-2013, 10:40 AM
Master Builder
 
Join Date: Mar 2008
Location: Washington State USA
Posts: 768
Default Re: Oven opening size

Mikku,

The height of the opening relative to the height of the interior of the dome is for optimum airflow. IMHO the depth of the oven plays an important part for proper airflow. One would expect that there is an optimum range for this distance but honestly I know of no study that has been done to determine this optimum.

There is skill and art to firing a WFO. The size of the fire and dryness of the wood being burned is important. Once the smoke leaves the interior of the WFO it is not really participating in the airflow inside the WFO; excepting if the flow is restricted to the point of choking the exhaust exiting the WFO. Regardless if the WFO is well designed and built, if the fire is producing a larger volume of smoke than the chimney can handle it will spill out the front. This a variable controlled by the person firing the WFO.

I see no problem with your referring to the area between the exterior opening and the interior opening to the oven itself as the landing.

The height of the exterior opening is IMHO more a matter of practicality in ease of working the food and fire and aesthetics of the builder. When I am firing my WFO I use a draft door and the opening is a bit over two inches high. It causes the fire to draw extremely well yet would be very impractical to try and cook thru this small an opening.

It is my feeling the depth of the landing has little to do with the performance of the WFO, with exception of how easy it is to manipulate whatever is being cooked in the oven thru the entrance and tend the fire.

The width has been discussed before. I suspect a controlling factor is one of support and construction in a traditional WFO built of bricks. The wider entrance allows for larger pizzas (provided we are talking of round pizzas).

Hope this helps,
Wiley
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  #25  
Old 01-20-2013, 02:03 PM
Master Builder
 
Join Date: Jan 2013
Location: Tochigi Prefecture, Japan
Posts: 590
Default Re: Oven opening size

Thank you Wiley,
I understand what you are saying about the distance from the inner door to the outer door - (landing) or transition - as a distance of convenience. Now lets call the distance from the inner door to the dome interior (or location) the "throat maybe". In your opinion is there any optimum distance or range that you must deal with?
I cast my dome in two pieces and a separate piece I call the transition. When I began layout for making an oven base it appeared like the "throat" was longer than what I see on all the photos at FB Forum. I spent a lot of time making the mold from wood but it would be modified easily for a future casting if this does not work out. Just trying to understand the mechanics of design...Now am beginning to understand the art of firing as well.
Still a very long way from puting a fire to anything. I can imagine it at best right now. Thanks again and Thank You Forno Bravo for hosting this forum--unbelievable wealth of information available!
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  #26  
Old 01-20-2013, 05:49 PM
Master Builder
 
Join Date: Mar 2008
Location: Washington State USA
Posts: 768
Default Re: Oven opening size

Mikku,
I don't see that there is any theoretical optimum distance. This is where it would be very hard to make a WFO totally heat tight. By that I mean the refractory dome is insulated everywhere save for where the brick transitions to the entrance (I'll look back but I think you referred to it as a tunnel). There will always be some heat loss thru the brick in this area and out the chimney. Now one can get very anal about some things but I think the loss thru the brick in this area is small, but honestly I have no data to support that contention.

Personally, designing this area so that one can easily place a door (hopefully insulated) to close off the interior of the WFO from the transition area is more important than making the area absolutely heat tight. Now for the disclaimer: In my WFO I made a wooden door that closes off the interior of the WFO from the transition/tunnel/landing. What I have was made as a temporary door. It was to test the concept. I was going (and perhaps will someday) to use it as a pattern and make a proper insulated door with some "art" etc. But as in many things in life, temporary which works often becomes permanent...well, at least for now. So far I have not found any pressing need for changing what I have, it's lasted several (like going on five) years. True, I cannot bake something two days after a firing but where I live wood is close to free and plentiful, I see little need. Besides pizza I've done turkeys and roasts and pork shoulders and baked and grilled and etc etc. It's easy and quick and fun and I could ask for very little more.

I would suggest making the entrance of such a size that one can easily "work" the entire area of the hearth. Not having a blind area, which is hard to clear of coals or ash or an errant roll which falls off the peel, would seem to be more of a goal.

Hope this helps,
Wiley
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  #27  
Old 01-21-2013, 02:21 AM
Master Builder
 
Join Date: Jan 2013
Location: Tochigi Prefecture, Japan
Posts: 590
Default Re: Oven opening size

Hello Wiley and thank you for all your help,
What I am making is entirely castable, the only part that will be brick is the floor of the oven and if I decide to make a decorative arch. I wish I could send a photo but my camera takes photos that are so large (2MB) each that even e-mailing sometimes is a problem.

The dome is in halves; the back half is just a dome (made using trapazoid shapes), sometimes the dome shape is called a trapezium...(there is a net page that shows how to calculate the piece sizes and angles.

The other half is the section with the oven opening. But this section extends away from the dome ..maybe 6" and as the dome slopes away, that distance gets larger. I formed a recess at this face to accept an inner door in the future.

The third piece of this WFO is the section containing the transition to the chimney. I made the casting so that it would overlap the #2 dome section at the opening by 2"--like a shiplap joint. I also made it slightly larger , maybe 1/4" on the sides. I planned on puting some kind of a fiber seal there that would make some kind of a thermal break between the oven itself and the transition/chimney/landing area. When the assembly is complete, there would be an outer door that would enclose the landing/transition/chimney section.

My thoughts are that the inner door is off for firing and baking things like pizza. The outer door would be closed for firing but with some kind of a air damper to control the amount of combustion. If I wanted to retain heat in the oven for bread baking--then the inner door would be placed in the recess provided.

I have not made any decision on the type of dome insulation yet. It all depends upon the price of the different products. I would like to use a ceramic fiber blanket for maybe 2" and then covered with perlite/portland insulation maybe another 4".

The area beneath the fire brick floor same undecided. Minimum 4" of perlite/portland. There again have to find the materials and prices. All this is a little more difficult locating in Japan and trying to communicate your needs to suppliers who up to now have not sold some of the products. A real learning curve.

Today was cutting metal to make a frame around the structural slab. I am making things indoors because of the weather and then will bring it outside to its final destination when the weather permits.

As far as the dome goes, all surfaces: dome, interior entrance, and transition to outer door opening will have the same specs for insulation. Final coat some type of stucco mixture for semi-waterproofing. There will have to be some type of roof to protect the entire WFO from the elements. We get huge amounts of rain here June and July.

Thanks again ---sounds like you really enjoy making great things to eat in your oven. I am looking forward to trying mine out this spring!

Yes, your input helps,
Mikku
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  #28  
Old 01-21-2013, 02:27 AM
Master Builder
 
Join Date: Jan 2013
Location: Tochigi Prefecture, Japan
Posts: 590
Default Re: Oven opening size

Short note:
I know that everything is available from Forno Bravo, but there is no dealer in Japan- closest are the guys down south in Australia--but toss up USA or Australia??? I know that a lot of the bricks sold throughout the world come from China as well as the ceramic fibers but most things from China require pretty large minimum orders (unless you get some sent as samples)... Duty is a killer as well as Freight and Customs inspections. Plus,plus,plus and pretty soon out of sight for costs!

Finding things locally or getting a Forno Bravo dealer locally are the options. Maybe in the future we will have a local guy to call!

cheers to all!
Mikku
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  #29  
Old 01-21-2013, 08:40 AM
Laurentius's Avatar
Master Builder
 
Join Date: Nov 2010
Location: Japan
Posts: 825
Default Re: Oven opening size

Hi Mikku,

I built my oven here in Japan and got everything that I needed, my oven is not casted. What are you having problems locating? Maybe I can help?
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  #30  
Old 01-21-2013, 03:35 PM
Master Builder
 
Join Date: Jan 2013
Location: Tochigi Prefecture, Japan
Posts: 590
Default Re: Oven opening size

Hello Laurentius
I am surprised! Another English speaker,living here,with an interest in WFO and with the skills or motivation to build one! Each quality makes the community smaller and smaller (very small percentage of population)! In any case great hearing from you.

Right now Perlite is high on my list, the stuff I found is both "B" and "C" grade
with "C" being the larger particle. This is from a local specialty masonry retailer. He had some in stock and could order more quickly. I will talk to one of the guys who grows and sells "vegetable transplants" to see if he could locate horticulture perlite/vermiculite for me.

Then there is the fire brick and ceramic fiber products. I found sourcing but need to compare prices. To date, I haven't made a trip to the Joyful Honda in our area.

My area has kilns for the processing of copper so everything necessary for WFO making should be available. I think that the people who repair them are no longer local. Also there are a lot of ceramic kilns not too far away, I think the town is called Mito?

Any insight you can give for locating products would be great. I like to research price as much as possible--money is always hard coming in and fast going out! Talking to find the "best price" usually pays big rewards!

Thanks
Mikku
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