How do you size an oven for bread making?

[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?

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?

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.

[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

[Faith In Virginia]

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

Nice to meet you Gary, I like new feet :-)

[mikku]

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

Thanks Mikku,

I just did not want to start something new.

Jay and the others have made some good points so I will add my perspective.

Bread is a totally different beast for the WFO and if your looking at a bakery that adds all kinds of issues.

I think we all have seen that oven with the chimney coming out of the baking chamber and the last one had smoking problems trying to force everything through a 4" vent...so no telling how that other oven was built.

To determine size you need to know the needs of the customer. How many loaves and what kind need to be baked on a single firing. Most bakery bread ovens have a large thermal mass usually 7 to 12 inches thick in the walls and floors. So they do take a while to heat up.

Now here's the rub, unlike pizza the operating temperature of the oven is critical. With pizza you get it hot and keep throwing in more wood to keep cooking temperatures. With bread you have a narrow band of usable temperatures. 575 degrees and your burning bread ...325 degrees and your crust looks like milk. This is why most bakeries plan to put in the higher cooking temperature bread in first and as the temperature drops puts in bread with lower cooking temperature requirements. It's all about oven management.

Now any load of bread puts a real drain on the available heat. 10 loaves at 1.5 pounds has about 1.2 gallons of water that needs to get heated just by the stored energy of the oven. So you can see that 50 loaves is like pouring in a 6 gallon bucket of water in your oven and try to keep your operating temperatures to where they will still cook bread.

Then you need to know how they like to bake. One big load or smaller multiple loads.
my 42" oven does 10 loaves easy that's 9.6 ish of square feet. But the 1.5 square foot per loaf is a good number for long loaves an loaves of different sizes.

With that you and the owner should be able to figure a good size and oven mass. I almost forgot available space to put the actual oven. Think that's a no brainer.

Things to keep in mind when designing a bread oven, lower ceilings are good for keeping more steam available to the bread. Also if they use sheet pans have the oven door large enough to get the pans through...with that also make sure the oven floor can hold the pans in the way the owner wants. nothing sucks as bad as having a sheet pan that won't fit by inches. Also don't build an oven larger then they can mix dough. If they can't fill the oven then the oven should get smaller.

I don't think it makes a real difference between the barrel and round ovens as far as baking but I think the barrel ovens are easier to load...especially a large oven.

Hope that gives you some idea of how to figure out the size and mass.

Faith

Thank you--lets try starting off on a new foot! Hi my name is Gary, I'm glad to make your acquaintance, my nickname is mikku--in Finnish it means "Michael". Let' see if we can solve some problems and have a little fun along the way!

[mikku]

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

Are the principles for a dedicated bread oven same as pizza oven?

Insulated floor
Insulated walls
Ratio door opening to dome (barrel) interior height same
No ratio on oven opening--biggest for maximum access
Ratio of oven opening to chimney cross sectional area
Chimney venting to front--outside of firebox; except for instance where a chimney can be physically closed after firing--then OK to be within firebox

I'm thinking of an alternative method of making a barrel oven using castable; maybe another prototype.

[mikku]

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

Just spent 30 minutes typing in a post and lost it!
I'll try again another day.
Thank you for those taking the time to give their responses, I know each of you have a busy schedule and I appreciate you sharing your time with me.
Thanks again!

I viewed the bakers' oven tonight--still not complete but I thought had some critical flaws.

Has anyone ever seen a commercial WFO oven with firebox at bottom? Where vapors/smoke/etc must meanander upward thru staggered shelves then exit from top? Will that design ever work?

I'll try to make several short posts as not to loose a lot of work over a missed keystroke.

[Bacterium]

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.

[texassourdough]

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

Well said Faith!

I will return however to my previous position... A commercial entity needs to figure out what they need and decide for themselves. I am not about to say what a commercial baker needs or wants because: 1) I am not a commercial baker and 2) even commercial bakers have different needs and expections and 3) I refuse to be your scapegoat for not doing your own research and reaching your own conclusions!

That said, Faith highlights one of the CRITICAL issues which is heat load/release. I can build an oven that will be TOO insulated and TOO hot TOO long. Example: I can build an oven that heat loads to 800 degrees and is still 650 tomorrow morning. That is NO GOOD! It is too hot for baking. As awful as barrel vaults are for pizza they are great for three batches of bread every day! A little extra insulation over the Alan Scott standard would probably be good for MOST applications. But too much could be a real problem.

THE OWNER NEEDS TO DECIDE HOW THE OVEN IS TO BE USED AND OPTIMIZE IT APPROPRIATELY and no one should accept responsibility for his decisions for he is the only one who knows what is expected and (perhaps) how it is to be used! For an oven like this it is too easy to build a "wrong" oven and then blame the person who told what to build.

A cast barrel vault may be asking for trouble for the thermal differential and expansion through the vault may be a source of cracks and problems. I have no experience in that area so I don't know how serious a problem it is likely to be. But I do I think serious research is appropriate and asking here is a good start.

jay

[Faith In Virginia]

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

Thanks Mikku,

I just did not want to start something new.

Jay and the others have made some good points so I will add my perspective.

Bread is a totally different beast for the WFO and if your looking at a bakery that adds all kinds of issues.

I think we all have seen that oven with the chimney coming out of the baking chamber and the last one had smoking problems trying to force everything through a 4" vent...so no telling how that other oven was built.

To determine size you need to know the needs of the customer. How many loaves and what kind need to be baked on a single firing. Most bakery bread ovens have a large thermal mass usually 7 to 12 inches thick in the walls and floors. So they do take a while to heat up.

Now here's the rub, unlike pizza the operating temperature of the oven is critical. With pizza you get it hot and keep throwing in more wood to keep cooking temperatures. With bread you have a narrow band of usable temperatures. 575 degrees and your burning bread ...325 degrees and your crust looks like milk. This is why most bakeries plan to put in the higher cooking temperature bread in first and as the temperature drops puts in bread with lower cooking temperature requirements. It's all about oven management.

Now any load of bread puts a real drain on the available heat. 10 loaves at 1.5 pounds has about 1.2 gallons of water that needs to get heated just by the stored energy of the oven. So you can see that 50 loaves is like pouring in a 6 gallon bucket of water in your oven and try to keep your operating temperatures to where they will still cook bread.

Then you need to know how they like to bake. One big load or smaller multiple loads.
my 42" oven does 10 loaves easy that's 9.6 ish of square feet. But the 1.5 square foot per loaf is a good number for long loaves an loaves of different sizes.

With that you and the owner should be able to figure a good size and oven mass. I almost forgot available space to put the actual oven. Think that's a no brainer.

Things to keep in mind when designing a bread oven, lower ceilings are good for keeping more steam available to the bread. Also if they use sheet pans have the oven door large enough to get the pans through...with that also make sure the oven floor can hold the pans in the way the owner wants. nothing sucks as bad as having a sheet pan that won't fit by inches. Also don't build an oven larger then they can mix dough. If they can't fill the oven then the oven should get smaller.

I don't think it makes a real difference between the barrel and round ovens as far as baking but I think the barrel ovens are easier to load...especially a large oven.

Hope that gives you some idea of how to figure out the size and mass.

Faith

[mikku]

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

The reason for this thread is because my supplier of refractory materials for my oven has seen how well my oven fires and the temperatures it reaches very quickly. His friend currently operates a small bakery using a "home made" oven that is not performing anywhere near his expectations. Takes 7 hours to fire, problem with smoke, cannot maintain baking temperatures. Made from local stone - "Oya" that pottery makers kilns are made. From the photo I saw, has a fire chamber at the bottom--stone walls, inner shelves... The heat rises through the chamber and exits from the top. A design I have not seen on this forum.
I thought that I might be able to build a modified version of my oven that might suit his needs.. or a barrel type.

The oven would be castable refractory, something that I think that I can form to any shape desired. It would be a fun project.

I feel I have no aptitude for bread making, even though I will experiment with things that can be prepared in a WFO.

[stonecutter]

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

You should read the book The Bread Builder's by Daniel Wing...

I loaned that out to someone and never got it back. It's a good recommendation...I miss that book.

[mikku]

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

Do you want my opinion?

Yes, of course!
I am sorry for previous hostile exchanges and my poor manners. I am not looking for a confrontation, only looking to learn something.
Please accept my apology.

[rsandler]

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

I am less expert than Jay or Faith in these matters, but I know some general principles, which I'm guessing from your other threads is what you're looking for at this stage.

The rule of thumb that FB seems to use in advertising their ovens is 1 1.5lb loaf per square foot, which matches my experience with a 36" Pompeii dome. I'm not sure if Polo is cramming them in tighter than I do, or if you can fit more loaves in a barrel vault oven with the same square footage--probably both. There is a WFO profiled in The Bread Bakers Apprentice that does upwards of a dozen batches per firing IIRC. Certainly you'd be able to get at least the 3 loads per firing that Polo gets.

For a dedicated bread oven in commercial use a barrel vault shape probably makes more sense, as it's going to be easier to load in bulk--commercial equipment exists for loading rectangular ovens, less so round ones.

Compared to a backyard pizza oven, a dedicated bread oven in a bakery is going to have lots more thermal mass, since rather than firing once a week and letting it cool down, it will essentially be constantly hot, and it's not a problem if it takes 3+ hours to fire it from cold and can't get above 500F.

Not sure about insulation--I'd guess that "as much as feasible" is still the rule of thumb.