Arch shape & depth

[CoastalPizza]

What are the pluses and minuses of the various arch designs? Deep vs. shallow? Open vs. closed sides? No flare vs. large flare?

Some ovens have relatively shallow arches with vents that stand proud of the oven - like the first two. Others are deeper - of these, there are some with flared openings (next two) - others have straight sided arches (fifth one). I've included a line drawing showing what seem to be the two extremes.

In all cases, it does seem to be a good idea to have an inner arch that is smaller so that a door registers against a solid surface.

Thanks, Brian

[dakzaag]

The arches you are referring to are actually called the vent area. The first two pictures are cantilevered vents that I have only observed in high end commercially built ovens such as Forno Bravo. I can only assume that a piece of curved steel lintel is specifically formed to provide support for the outer shell of the oven. Typically the outer shell provides a pathway for exhaust gasses to move to the chimney located in the center of the dome. This means there is a hollow area above the oven dome that allows smoke and hot gasses to exit the fire chamber and travel above the oven ceiling to the chimney and out. I believe this style is typically built using cast refractory and sometimes is referred to as a squirrel tail oven because of shape of the smoke path resembles a squirrels tail. I do not believe I have ever seen a cantilevered arch vent constructed from firebrick, but I'm sure someone will prove me wrong.

The next pictures are more typical of a brick vent with an inner and outer arch. The inner arch supports the dome and allows pizza to come in and smoke to exit. The flared or angled walls of the vent allow for better visibility of the action inside the oven, as well as a little more space to work the peel into the front corners of the firebox. The outer arch provides support for the throat and chimney of the oven. You are correct that the inner arch should be a little smaller and provide a lip for a door to seal against to retain heat. The advantage of a flared entrance is easier use and better visibility while cooking. The disadvantage is complexity of construction when building the outer arch. You want your arches to have maximum contact brick to brick since this is a high heat and high stress area. This means the brick need to be cut as perfectly as possible to obtain maximum contact with very little mortar. The first two brick of the outer arch end up being a compound miter cut which is pretty hard to accomplish without a lot of trial and error. If you get in a rush and just use mortar to fill in the gaps of the brick, then eventually the mortar fails and these brick become loose, leak smoke and possibly allow the arch to sag. This outer arch is the main support for the throat and chimney so if the arch sags, then the rest will follow and it is right at the front of the oven.

I would love to see someone post pictures of a well executed flared outer arch with tight joints. I have plenty of my own examples where it is completed, but not all that great in terms of tight compound angle joints. It just takes a precision that I don't have the patience for.

[CoastalPizza]

I plan on casting the dome, arch, & vent so complexity of the shape isn't as much an issue as it is with brick construction. Thanks - Brian