Sunday, December 18, 2011

Indoor Brick Oven Construction: The Throat

As stated in the previous posts, the throat will likely be the most challenging part of an oven project.  Even on cob ovens (see previous blog), special attention is given to the mouth and, when desired, the throat.
What goes into the mouth as fuel should, after burning, pass into the throat and out, otherwise, as is true at fraternity parties, it will spew out of the mouth and mess up the face.
 The first arch created the mouth. The second arch creates the throat.
In this oven, the same form was bulked up with blocks so that the identical arch could be extended outward to support the bricks at this larger and higher dimension.
Shims raise the form off the floor and a layer of cardboard makes removing the form after mortaring easy.

Full length firebrick is cut to form corbels, a stepped-in series of bricks that take the wide opening of the throat and bring it to its intended 9" by 8" dimension.
The next step in this oven will be constructing a flue channel that runs over the top of the oven so that the chimney, when installed, is set back from the face.

Friday, December 16, 2011

Indoor Brick Oven Construction: Part 3

The point where the dome meets the mouth requires the most custom attention. 
This oven has the angled brick mouth that allows easy access to the cooking area. This means that the bricks that 'spring' the arch need to be cut square to the face of the oven (an interesting geometric exercise). The tall butress brick assures extra strength to the side of the spring bricks.
If the mouth was constructed with angle-iron, the dome will be meeting the mouth along a straight plane.
If the mouth is an arch, it will meet the dome along that curved plane.
Either way, the goal is to make the meeting points rest vertically on the mouth and allow the dome to complete the circular shape that makes it strong.
As shown, I take advantage of the open front to bring the dome as high as practical before closing the front with the mouth arch or angle-iron. I then bring the bricks forward to meet the mouth, custom cutting the bricks as I go.

Eventually (next blog) the second arch will define the throat bringing the construction to the face of the oven.

Sunday, December 11, 2011

Brick Oven Mouth Construction

How appropriate for an object that makes food to have a mouth. One oven I repaired was fashioned in the shape of a turtle and the mouth was the mouth.  But seriously, very seriously, the mouth and throat of a brick oven presents the most challenging masonry techniques.

The requirements of the mouth and throat (the area just above the mouth in this case) include:
1. The easy and safe introduction of fire to the oven interior.
2. The smooth passage of smoke from the burning fuel out the chimney.
3. A shape that allows handling whatever is cooked in the oven with ergonomic logic.

The construction of a mouth that meets the above requirements varies. Many of my portable ovens have angle-iron lintels that carry the load and shock of a masonry unit in motion on the road.
The most appealing mouths have brick arches, usually with a slot above that is the throat. In both cases this throat area is larger than the chimney and channels flue gases up and out rather than having them spill in front of the face (the outer front) of the oven.

My original portable oven, although white stucco on the face, is still white after four years of frequent firings.

Angle-iron lintels are easy. The three heavy angle-irons lay level on top of the side bricks of the mouth.
Arched mouths must be built with an arch form and need sufficient side support to contain the outward force of the curved arch bricks.

Some ovens have deep mouths that prevent easy access to all areas of the cooking space within the dome. After observing ovens in Italy and France as well as baking in my own oven, I began building oven mouths that angle considerably from back to front. This allows the baker to access all edges of the interior of the oven without expanding the actual oven opening beyond the recommended proportions for efficient firing and heat retention.

Saturday, December 10, 2011

Indoor Brick Oven Construction: Part 2

Most brick oven domes begin with a straight course of vertical bricks so that the perimeter of the oven has the space needed for baking and for a live fire.
By cutting 4.5" by 9" by 2.25" fire brick at an angle through the middle of the brick, I get two identical bricks for the first course that provide the initial angle for beginning the dome.
Over time, I have found that a whipped-cream consistency of high refractory mortar lets me dip the edges of the bricks into a mortar bucket coating the bricks with a thin and even layer of mortar. This speeds up the process of applying mortar and laying the courses.

There is a 'middle process' that accompanies the first courses of the dome: the eventual arch supports for the mouth and throat.
These will addressed in the next blog in detail as they require some planning and may be built simply or elaborately.

The second course is laid flat against the angle of the first. From there up, pre-cut firebrick wedges and pre-cut angles on each brick provide tightly fitted joints. The wedge shape of each brick locks each course into place giving the dome an almost indestructible shape while allowing expansion and contraction to act in all directions at once.

Sunday, December 4, 2011

Indoor Brick Oven Construction: Part 1

I have become an advocate of interior brick oven installation (see October 31 blog). The next number of blogs will take you through the process of placing a brick oven in a residential kitchen setting. The construction is not that different from outdoor ovens. There are times (later this winter in an colonial era house) when a masonry base makes sense and the support already exists below the floor.

In this case a well-framed base and support beneath the floor combined with lightweight insulation materials and a lightweight exterior treatment permit the oven to sit as safely as any comparable weight appliance (such as a hot tub).

Foamglass, Fiberfax, firebrick
The materials used here are 2x half inch cement board over plywood base cover, 4" of Foamglass, and 2" of Fiberfax panel insulation board.
The base was measured and built so that standard counter-top widths and heights meet the exterior of the oven volume. A setback of the oven floor will accommodate a stone working shelf in front of the oven mouth.

In order to provide maximum space in the interior of the kitchen remodel, the outer framing of the oven enclosure utilized unused space in the corner of the garage (about 18" by 5') and a small bump-out on the back of the building.