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63"x63" Montreal-style Commercial Bagel Oven
This wood-fired oven for Montral-style bagels was built for the newest third location of The Bagel House - a successful Toronto bagel company. The company has two locations in mid-town Toronto baking some 44,000 bagels a week combined in 24/7 operations in their 10-year old wood-fired ovens built by a Montreal company. Bagels are prepared and baked according to the authentic recipe by boiling them first in a honey bath and then baking on the hearth, achieving unique characteristics a true bagel-lover would expect from an authentic Montreal-style bagel. Both owners, partners in the business, spent years working in the most famous bagel bakeries in Montreal prior to opening their own first bakery in Toronto.
Since owners are basically happy with the old ovens and I haven't had any previous experience with bagel ovens, design of the new oven was based on design of the existing two ovens at the company's other locations, keeping basic proportions and features essentially the same with some minor variations intended to improve existing design. Existing ovens are larger: one is 72"x 84" and another 72" x 96". The larger one had 9"-thick vault and was reported to be too large and not very efficient, slow to respond. The smaller one had 4 1/2"-thick vault and was reported to be just fine. Both ovens have 24"-high vaults, 2"-thick hearth over a layer of insulated firebrick on steel base, multiple chimney exits with one or two located in the vault opposite to the fire.
The resulting design of the new 63"x63" oven features:
- 24" high vault with reduction to 62% of the height towards front by stepping arches;
- 2 1/2" thick hearth over base heavily insulated with Foamglass and insulating firebrick;
- 4 1/2" thickness of the vault, plus 2" layer of castable refractory over the vault outside of the smoke chamber;
- 4 1/2" thickness of the walls;
- Extra chimney exit through 8" SS pipe in the vault (copy of the solution used in the old ovens) with own sliding damper;
- Smoke chamber on top of the oven, combining oven exits into a single volume vented by single 12" ID chimney;
- 40 1/2"-wide loading opening, shifted to the right according to old oven design, where fire is kept on the left, contained in the area by a heavy steel angle placed on the hearth;
- Improved primary and additional secondary combustion air supply system to improve combustion and increase efficiency;
- Ash dump system with large grate and dedicated damper;
- Heavy I-beam steel harness;
- Clay brick front face with cement board on metal studs facing on other sides with lots of mineral wool and foil insulation between the oven and the facing.
Oven is built over a 4" layer of Foamglass structural insulation laid on top of a reinforced concrete slab supported on a steel support system engineered and built by others. Foamglass is protected with Durock cement board.
Skew courses for stepping down arches the in reduction part of the vault and channel for secondary combustion air with outlets.
Skew courses are in for the complete vault. Note secondary air outlets in the wall below.
Hearth bricks are laid over additional layer of insulated firebrick in clay/sand mixture for easy removal should replacement of hearth bricks will ever be required.
First brick of the lowest arch, forming smooth reduction lip is laid.
The lowest arch is in place with the next one started on top. This one will form a throat.
The second arch(vault) is in place. Note: throat and grates over the ash-dump damper in the hearth.
The first and the second arches from below. Note angles for smooth transition.
The first and the second arches. Another view.
The harness is in place. The main vault is constructed.
Last bricks in the main vault.
Main vault is in place. Angled cut-offs are used to smooth-out a step in the future-to-be smoke chamber.
Sergei is cleaning the vault.
Finished oven inside. The first view.
Finished oven inside. View from inside.
Finished oven. Another view from inside.
Vault is finished. Before smoke chamber is built. Note: I-beam harness with additional support at the middle.
Vault from the top before smoke chamber is built.
View from the front. Note: square opening for primary air supply and the rectangular opening for secondary air supply.
Smoke chamber is built. Note: clean-out openings in its walls and a damper for the second chimney outlet in the main vault.
Top view of the smoke chamber. Chimney connection is at the end.
Castable refractory is used to smooth-out area around the damper to reduce undesired turbulence.
The area outside the smoke chamber is sealed with 2" layer of castable refractory.
Stainless steel liner used to reduce height of the extra exit to necessary 62% of the vault's height. The liner is embedded into castable refractory mix.
Steel studs form facing walls on the sides and top of the oven.
Multiple layers of mineral wool insulation with foil in between are laid over the oven's refractory core.
Finished oven.
Finished oven. Loading opening close up.
Alex Chernov
December 2008
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