The reason an island is not advisable

[jcg31]

The article on building an island of firebrick under the firebrick floor of the oven says "This design is not recommended for basic back yard cooking, is useful for bread bakers who want their oven to be fired longer and hold heat longer for multiple batches of bread baking from a single firing."

With all that I have read about the challenge of maintaining the heat of the floor this would seem a good idea for any application. Does anyone know the reason the artical advises against it for "basic back yard cooking" and if it is start time, how much longer doe it add to the time to bring the oven up to temp? If it it fuel, how much more?

Thanks for any help

[asudavew]

Re: The reason an island is not advisable

It takes longer to heat.

Meaning more wood and time. It takes sometimes 2 hours to heat just a single layer, some people can do it in about an hour.
A lower layer would suck heat from the top layer but supply more to the upper layer after the fire is out. But if you are planning on baking lots of breads its a good option, but for pizza one layer is best from what I have read.

The first builders on this site would pour their insulating layer first, then the structural concrete on top to add thermal mass to their ovens. I am sure some of them will weigh in on their heat up times so we can compare heat up times to the newer design.

[maver]

Re: The reason an island is not advisable

With all that I have read about the challenge of maintaining the heat of the floor this would seem a good idea for any application. Does anyone know the reason the artical advises against it for "basic back yard cooking" and if it is start time, how much longer doe it add to the time to bring the oven up to temp? If it it fuel, how much more?

Thanks for any help

I would argue that the 'backyard cooking' challenge is getting the oven to temperature quickly - I have very little trouble maintaining heat during typical use - you can even step away for a while by putting the door on with a small crack for ventilation after tossing on a log or two. If it takes more than an hour to heat up, are you ever going to consider using it on a weeknight? If your weekend is busy and you are not around for several hours for preheat for an oven will you use it during the weekend? Remember that during heat up you are adding wood to the fire every 10-15" and using a big fire. I usually use more wood in my heat than I do for pizza making. If you double the heat up time by adding more thermal mass you might end up almost doubling your wood consumption per bake.

With the standard pompeii plans it's reasonable to expect about an hour heat time. This gets you to pizza temperatures, and if you maintain the temperature for an hour or so your thermal mass will be fully soaked with heat to allow a slow temperature drop and plenty of time in the bread range to bake a few batches (a high and a lower temperature bake - if you need to do two batches at the same temperature, you may want more thermal mass).

If you want to bake bread for home use and are ok with 5-10 loaves a bake (relatively easy to fit in a 42" pompeii in a single bake) then the regular pompeii plans are excellent. If you are considering using the oven to make more than that (such as for sale at a farmer's market), then consider more mass.

Dutch, Jim, does that sound right? Dutch, how many batches do you do in your high mass oven, and how many loaves per bake? Anyone using the standard pompeii regularly for semi-commercial use? Drake, I know you are using it regularly for bread, how many loaves can you do well in a firing? I've done 10 loaves comfortably in two batches with plenty of room, but I don't bake that much regularly because I like to keep it fresh and have not established a supply chain to share bread with .

Marc

[Archena]

Re: The reason an island is not advisable

Might wanna consider how you're planning to use your oven as well. Myself, I imagine it will be mostly when I'm having friends over so I'll want to get the most out of any given firing since there won't be as many. Also, I may bake for feasts occasionally (Society for Creative Anachronism - the Medieval version of the Civil War re-enactors - only we were first!) which would be bread for 80 - 150 people (average) possibly including breakfast (if I'm feeling fancy). For that I'll definitely want the high mass so I'll probably go ahead and build it that way.

Yes, I'm weird.

[jcg31]

Re: The reason an island is not advisable

Thanks for the input folk, For my purposes I'll stick to the single depth floor.

[DrakeRemoray]

Re: The reason an island is not advisable

IDrake, I know you are using it regularly for bread, how many loaves can you do well in a firing?
Marc

I have baked as many as 16 loaves in a single firing. including some 4lb Sourdougs in that mix...I have a little extra mass, maybe 1-2 inches of refractory on the outside of my dome...

Drake

[CanuckJim]

Re: The reason an island is not advisable

JCG, Maver, Drake,

When I get my high mass oven up to heat, I can get six to eight bakes out of it. I do this by starting with baguette, about two dozen, then two bakes of hearth breads, then two bakes of batard, then pan breads or bagels. There's still plenty of heat left for rolls and such if I have time. Then again, I have seven inches of mass both below the floor and above the dome.

I think Maver has got it right on. One to two inches of refractory on the outside of the dome is a good compromise and will give you enough mass to increase the number of bakes without adding lots of time to the firing (probably about two hours, rather than one). This is exactly the procedure I'm following with my oven customers who want to do a lot of bread baking and general cooking beyond pizza.

My deck is four feet by three feet, so I can comfortably load a dozen one kilo round breads at a time. Sometimes, I'll load breads near the door at the same time that don't require such high heat.

Jim