Thermal mass across whole floor or biased centrally ?

[uk_exile]

Is it better to have more thermal mass across the whole cooking floor, or biased towards the middle ?

Thinking about my first build using a kitset that is predominantly insulating type bricks with the central area of the cooking floor being a heat retaining tile. A FB member has suggested increasing the area of cooking tile however I?m wondering if doubling it?s thickness is better.
More info, photos etc here http://www.fornobravo.com/forum/f6/a...and-18801.html

[ATK406]

Re: Thermal mass across whole floor or biased centrally ?

I have a uniform thickness of insulating bricks with a firebrick floor. However I find it is helpfull to move the fire around within the oven to uniformally heat the floor and dome. I usually start in the middle and then move the fire to the right and then finish heating the oven on the left.

In the end, the dome is at a uniform heat and the middle of the floor tends to be hotter than the rest of the floor. That is where I would concentrate my thermal mass if I were going to limit the functional area of my cooking surface (which I wouldn't do unless I absolutely had to).

That said, I find it is helpful to have areas of the floor that are a little cooler such that I can juggle a few pies in and out of the oven at the same time (or pour a beer) without burning the bottom of the crust. IE If the center of my floor is at 700, areas around the edge are only at 600 and I can cook pizza and calzones (which take a little longer with less worry about burning the crust).

[uk_exile]

Re: Thermal mass across whole floor or biased centrally ?

ATK406, I assume the middle of your floor is getting hotter than remainder of floor due to dome heat reflection. Does that hint toward it being better for me to add more heat retention in the middle rather than making the whole floor heat retaining ?

[ATK406]

Re: Thermal mass across whole floor or biased centrally ?

Good point, that may be a factor too. Yes, you want to maximize heat retention in the area where you will be doing most of your cooking. But you don't necessarily want to create a heat sink right in the middle of the floor. The advantage of spreading out the thermal mass across the whole floor is that you can cook on it and it will heat up more quickly/efficiently with the fire vs relying on heat conduction through layers of brick. Is fire brick very hard to come by in your area or cost prohibitive? Or is it just a hassle to reconfigure the floor layout with the bricks and the kitset?

Regards,
AT

[uk_exile]

Re: Thermal mass across whole floor or biased centrally ?

High density fire bricks are $5-$6 each here in New Zealand ..................major reason why I'm interested in this kitset as all up it's less than just the bricks for making a Pompeii !!!

[uk_exile]

Re: Thermal mass across whole floor or biased centrally ?

Maybe I could improve the design at relatively low cost by installing the bottom full insulating layer as per plan, then the second layer of central cooking tile and outer insulating as per plan, then add an extra third layer with cooking tile over whole (or almost whole) of the dome floor area. Thoughts ?

I've asked the seller what the heat loss vs time is. Waiting on his response. Unfortunately not a local business, it's a flight away :-(

[ATK406]

Re: Thermal mass across whole floor or biased centrally ?

Sounds reasonable. That would also increase the size of your cooking surface. You might even be able to cut the third layer of cooking tiles in such a way that you could remove them if they slow down your heat-up time too much. And you could put them back in when you think you need more thermal mass. May be a bit of a pain but might give you the flexibility you are looking for.

What is the cooking tile made of? Is it ceramic? If so, that might be hard to cut.

AT

[uk_exile]

Re: Thermal mass across whole floor or biased centrally ?

Clever idea ! I don’t know what the tile is made of. I’ll ask

[Tscarborough]

Re: Thermal mass across whole floor or biased centrally ?

The floor is the hardest area to fire, and for a low use pizza oven, the thermal mass should be minimal, 2.5" bricks laid as pavers for the hearth, with good insulation will work better than localized mass or thick floors.

[uk_exile]

Re: Thermal mass across whole floor or biased centrally ?

Thanks Tscarborough, maybe I'll just go fo the kitset exactly as supplied as aim is for convenient use.

Here's the info I received re cooking tile.
Heat Sink Tile
The heat sink tile is an additional, unique feature of the Deco Wood Fired Oven. The tile is supplied in x 2 monolithic halves and has a hard, ceramic-like cooking surface. It has also been designed to absorb and retain intense heat, releasing it slowly after the combustion process is spent. It is akin to cooking on stone.
The tile is manufactured from a composition which has a very high thermal-mass. Because of the cyclic changes in temperatures that the tile is subject to (ie. heating/cooling), and that it absorbs moisture from the atmosphere in between oven firings (ie. water turns to steam and can’t escape), it is highly likely the tiles will develop surface fissures and may occasionally, fracture. Any such events will in no way affect the performance of the files and/or, oven. We have made the tile a few mm thicker than the insulation tiles for greater heat retention, and for ease of clearing ash. The tile surface is covered with a thin film of beeswax to assist in curing.

[brickie in oz]

Re: Thermal mass across whole floor or biased centrally ?

Here's the info I received re cooking tile.
Heat Sink Tile
The heat sink tile is an additional, unique feature of the Deco Wood Fired Oven.

Rubbish, this is how all wood ovens work.

The tile is supplied in x 2 monolithic halves and has a hard, ceramic-like cooking surface. It has also been designed to absorb and retain intense heat, releasing it slowly after the combustion process is spent. It is akin to cooking on stone.

Like a normal wood oven

The tile is manufactured from a composition which has a very high thermal-mass.

Like a normal Aluminium oxide firebrick you mean?
The same stuff that gives you cancer according to their website.

Because of the cyclic changes in temperatures that the tile is subject to (ie. heating/cooling), and that it absorbs moisture from the atmosphere in between oven firings (ie. water turns to steam and can’t escape),

Rubbish, most water in an oven turns to steam and burns off, its the quick generation of steam in the refractories that cracks them.

The tile surface is covered with a thin film of beeswax to assist in curing.

Which will burn off at the slightest hint of a flame.



The crap that people spin to sell stuff is just unbelievable.
Get the plans, build your own oven.

[uk_exile]

Re: Thermal mass across whole floor or biased centrally ?

Get the plans, build your own oven.

Thanks however I have the Pompei plans, they're the ones that really sparked my interest a couple of years ago and I would just build off them if the bricks weren't $6 each making the build 3x the cost what these alternative designs are.

I'm not wanting to compare this kit's performance to a full on high mass pompeii type design as I know it won't be as 'good'. However I'm willing to sacrifice some aspects such as really long slow cooking in favour of quicker heat up, less wood knowing in return we'll use it more often & will save money both building & operating it. I'm trying to compare it's performance to a steel box 'pizza' oven that sells for similar money (or often more).
Wood Fired Pizza Oven | Trade Me

Is the fozmex kit design 'good' enough ? Can it be 'improved' by adding a little more mass ?

[Tscarborough]

Re: Thermal mass across whole floor or biased centrally ?

I can't believe that you can not find 200 solid common used brick for less than 6 bucks ea. Use them for the dome and buy enough fire brick for the floor, and you are gold.

[uk_exile]

Re: Thermal mass across whole floor or biased centrally ?

I didn't think common bricks could be used. I read somewhere that when heated they shoot little bits of brick off their surface & hence ruin the food. Splay is the term I think

[Tscarborough]

Re: Thermal mass across whole floor or biased centrally ?

"Spall" is the correct term, and if they are old solid brick, they will not spall under normal conditions. They will eventually erode (similar to spalling, but at a microscopic scale), but that is a long slow process.