Thursday, February 18, 2016
Building the Brick Oven Dome
Three thousand years of brick oven use has proved that the dome is the most efficient and durable shape. This is true of all European ovens, most Middle Eastern ovens, colonial north American ovens, and is also the shape of the cob and adobe ovens of Africa and the American southwest Native tribes.
Now that this detail is out of the way, how is this done?
I recommend that a stable base be built that allows the baker to access the oven mouth without stooping. This usually means that the floor of the oven is from 40" to 44" from the ground.
Skipping the insulation detail at this time, see: (http://truebrickovens.blogspot.com/2011/12/indoor-brick-oven-construction-part-1.html), the floor is laid out herringbone pattern so that the metal peel cannot catch on any minutely higher edges of the brick. On this, the dome is built. Many builders use a form at this point because eventually it become difficult to set bricks at extreme angles without them falling.
A form is recommended for first-time builders. These can be made from a pile of sand, removable sections, a burnable wood form, or other accurately cut materials. I don't use one. If arch bricks are used to form the dome, the joints between bricks should be thin enough so that they adhere with properly mixed refractory mortar. It's not easy though. Accuracy of cutting the bricks is essential.
Pre-cutting the bricks speeds the process. I have a CAD design that indicates angles.
An important aspect of dome building is the mating of a half-sphere with the arched mouth of the oven, something that needs to be fitted when the oven is built.
Two options are: Cut the mouth arch to receive the courses of brick at that level OR cut the bricks at that level to conform to the top of the mouth arch. Don't try to pre-guess this. It's easier (still hard) when you get there. By mocking up the mouth arch you can scribe the cuts necessary.
A 'Keystone' closes the top of the dome. If properly fitted, the dome brick joints will be as tight on the outside as the inside. If not, the next, insulating concrete shell will cover the gaps.
Whether you use a form or not, getting inside the dome will insure that any gaps are filled and any loose mortar is cleaned off.
Be sure to have someone nearby in the event that you swell after crawling in.
Many other posts on this blog contain detailed information on dome building. Good luck.