How do you size an oven for bread making?

[cobblerdave]

Re: How do you size an oven for bread making?

Gudday
I have seem an scottish side draft oven in my youth . Sorry I didn't understand the niceties at that time. But I do remember the firebox was at one end the smoke exhausted across the curved roof to a chimney at the other end. I would guess the chimneys entrance hieght would be at 63per cent of the ovens roof height.
Had sliding steel doors in the front which were low and wide and most probably well lower than the level of the chimney entrance.
Hope my memory serves me
Regards dave

[mikku]

Re: How do you size an oven for bread making?

Mikku......going slightly left field of current post responses.
have you ever discovered some of the older posts by CanuckJim.
Sure oven development on here has been moving forward constantly but I found his stuff informative.......don't know much about where he is actually at nowadays because I went "away" from here for
a while.

A quick search and it seems like he is doing quite well. As resident baker on his own homepage and affilliated with fornobravo in the sales and construction of multiple WFO in Canada.

Looks like participants to this forum have prospered on their own and their exposure has boosted them in other pursuits.

I'll have to study previous posts to pick up information imbedded.

[mikku]

Re: How do you size an oven for bread making?

Report on local bakery:
I met the local baker and saw his hand manufactured oven.

Specifications: (about)
-approximately 4' wide x 6' tall--maybe 4' deep

-lowest section the firebox
-upper sections were shelved with double doors to each section--full width

-internal shelves; sometimes went entirely to back with front not full depth;
other shelves flush with front- not entirely to back

-designed so that heat/smoke/vapors etc. from the lower firebox section had to meander upward and zig-zag through the oven before finally exiting from top.

-lowest section (firebox) had fan assisted intake air--maybe 4" diameter
-chimney or flue--2 ea 4" diameter exhaust vents near highest point of oven

-oven construction---a cage of steel angle; onto which door frames are attached; lowest firebox--next progressing upward (double doors) 4 high

-into this framework- oya stone slabs are inserted---as walls and shelves

-oven doors have a loosely installed fiber gasket to seal door entrance

-absolutely no insulation of any kind on entire oven.

[mikku]

Re: How do you size an oven for bread making?

Bread bakers complaints or report on oven operation:

- oven takes a very long time to heat up--sometimes up to 7 hours with oven temperatures rarely exceeding 300 deg C

-problem with smoke

-interior oven covered in a thick layer of soot

[mikku]

Re: How do you size an oven for bread making?

My observation and recommendation:

-I thought that location of air entrance should be firebox door rather than a different location--making drafting more controllable.

-I thought that chimney size was not adequate--suggested changing to 8" or larger and increasing height of chimney!

-recommended building a steel stud enclosure around the oven; clad with a non combustable material; and then the cavity between the wall and oven--filled with loose fill perlite or vermiculite

-recommended lining oven shelves and wall sides with firebrick

-recommended adding insulation to the oven doors to make them more capible of retaining heat.

--the baker is scheduled to open the new entity--around the end of June or the beginning week of July.

I offerred the use of my oven--only needs to be transported to his house/bakery via boom truck and set down. He paid for transportation only! This is just to acquaint him with a well insulated oven compared to his build!

[mikku]

Re: How do you size an oven for bread making?

My thoughts on the oven:

-better to tear the entire thing out and make a barrel type oven sized for his mixing capacity and sales needs.

-short of that; I felt that he would never get a great functioning oven.

-the baker spent a whole lot of time making this oven...hard to accept advice from a foreigner and squash his dream oven plans!

I told him that I could help him--but in the end; I felt the oven would always need a lot of maintenance and would always consume great quantities of wood!

[cobblerdave]

Re: How do you size an oven for bread making?

Gudday
I did a little hunting up to find out what does make a bread oven differ from the forno ovens we build. I found s confusion of things ...plenty of adds to. The main thing seems to be as Faith said ....mass .
The Formos are a small oven and I think rely on the insulation to make them work well enough for the heat we put in them. The bread ovens are as I remember them massive. The one I found was Red Beard Baker in Victoria Aust.
60 tons of brick and sand held together with steel rods least the Expantion pull it apart. 16 sq mtr of oven hearth under a domed roof which once fired can produce 1000 loaves from a single firing.
I suppose when you think about it heat moves througho a mass at the same speed . A small oven it travels and is lost quite quickly unless hypa insulated. With a big oven like the red beard one the heat would be held in the mass for a longer time just due to the thickness of the thing. The sand rather than insulating as such would allow the heat to escape from the oven face at a slow rate due to the amount rather than the efficiency.
Anyway watching this post with interest
Regards dave
PS you baker friend sounds like is trying to build a traditional oven on modern lines . The multiple decks and shelves are a design of modern gas fired bread ovens. Pherhaps you could point out to him that a more traditional design would work better as the design goes back many centuries . The Japanese respect tradition and bread baking is not I would think a traditional Japanese thing

[mikku]

Re: How do you size an oven for bread making?

Bread making in Japan may have a long history, dating to the times first foreigners were allowed entrance. Bread consumption by the general public has a very short history--a lot to do with the end of WWII, Pacific War and beginning the new Japan we know today. The USA promoted use of wheat to boost our exports to Japan. Now, Japan is trying to modify the appetites of their population by formulating bread based on rice flour.

This bakers' idea of WFO baked breads and bakery items in this tourist area is probably great. If you can make your product "A BRAND"--if you know my meaning. People will buy it by name recognition only and pay a premium as well--at least here.

[mikku]

Re: How do you size an oven for bread making?

At this point in this bakers' business plan...I think that modifying his present oven--adding firebrick to his shelves; additional brick oven walls; and trying to create a better flow of gasses through his oven when it is firing are minimums that can easily be accomplished.

The additional brick adds some mass--if mass is the biggest issue, it can be easily added to exterior.

I do not know what kind of wood he is using for firing--maybe a straight hardwood would help cut down on soot.

I have never seen the inside of a commercial wood oven in operation--is it soot free?

[cobblerdave]

Re: How do you size an oven for bread making?

Gudday
Soot is not a problem I would think as the smoke and heat pass through the domed roof where its burnt off in that high heat zone. Think of you own domed oven . Light a fire and you get a lingering layer of smoke forms above the floor in a layer till the heat builds up in the dome and it suddenly disappears.
Do you think those shelves would be a contributing factor to the build up of soot? As there is no one surface to get super hot and radiate the heat back to complete full combustion of the smoke?
Regards Dave
Thanks for the insite on bread in Japan , I visited 29 yrs ago and at that time the only bread I can remember was a Macdonalds bun!

[mikku]

Re: How do you size an oven for bread making?

As I said in a previous post, I have never seen a commercial bakery oven--at least a WFO type. There was a bakery near my workshop in Minnesota. His oven was a steel shell fired by natural gas and the rack that held his baking items were on a ferris wheel type of contraption. The racks would be added and on one side--possibly removed on the other--as they moved through the oven.

My oven when I start it smokes a little and soots up the dome every time it is fired. At some temperature--that I have not determined--the soot just disappears, that is every firing cycle. I have small remnants of soot where the smoke and gasses leave the oven and exit by the insulated ss chimney.

The soot that I observed at the bakery, hung off everything in the oven (like cobwebs and dust in a very old building)- I think that he is using a poor quality wood; lack of proper venting so the smoke just hangs in the inside of the oven and whatever contents it holds just cling to the interior cool surfaces- I don't think that the fire is really burning properly. I just have not seen enough ---or there are just too many little factors that are not working.

Possibly if he had LP burners in the same configuration, it would heat better--but even LP soots without the right air to gas ratio.

Costs of fuels in Japan per BTU have Electric being the highest, LP and LNG being second, kerosene third, heavy oil (like fuel oil fourth)--I do not know wood costs to compare...If the wood had to be all purchased, it would be considerable as well!

I think the baker is trying to make a niche business with wood fired bread baking. I'll let you all know what I find out the next time I talk to him.

[mikku]

Re: How do you size an oven for bread making?

There are all kinds of bread in Japan--if you call "store bought" bread or cooked "white paste".

There are a lot of sweat or filled breads you can get at convenience stores.

There are a few very good bakers of sourdough hearth bread like Laurentius, if you talk real nice to him, you might get a taste of his specialty.

I get Rye bread made with molasses regularly from our regular oven--only once from our WFO--and in a very dark version--called CHARBREAD--because it resembles charcoal more than bread...My mistake burnt bread.

A regular treat for kids is Hokkaido milk bread...very light, soft and sweat. so there is some room for bread making here.

[vtsteve]

Re: How do you size an oven for bread making?

Check out this thread on The Fresh Loaf: Semi Commercial WFO in Progress | The Fresh Loaf - it's strongly influenced my plans for my next oven...

[mikku]

Re: How do you size an oven for bread making?

Thanks for the information on the oven built by sgregory. That guy has a whole lot of talent--it shows in his oven construction and attention to detail. I see that there are other familiar names posting on this thread. I will have to take the time to search other things that are available through that forum. Thanks again!

[mikku]

Re: How do you size an oven for bread making?

Over the last week, have been doing a lot of thinking about this bread oven.
Now I am thinking about casting one based on the design in the previous link.
I think all of the bases can be covered quite nicely until getting to the oven door. I am assuming some type of loading device would be used to get the bread in and out of the oven quickly--so the door should be something that can open and close quickly and open only to the height required for loading. My thoughts are toward something that would slide up and down, probably cast also--so it would be quite heavy (with insulation and outside shielding). There would have to be some kind of track assembly and counter weights to assist in opening and closing.

Does anyone have any thoughts on oven doors for an oven with possibly a 4 foot wide opening? This would be a smaller version of the previous link but still would be able to produce a lot of bread.

Is there a lot of advantages of having an ash dump to the side of the inside of the oven?