This project has its roots in the original 'Wood Fired Brick Oven,' which the Kaslo Sourdough Bakery started out with in 1991. The wood fired brick oven I've built, seen here, is similar to the oven I used then. The oven has a number of innovative design features that I worked out to maximize practicality, efficiency, and the joy of baking with it.
- The oven sits on a one-piece concrete base, and can be moved if ever the need arises, therefore semi-portable.
- The front of the oven is designed and built in steel plate verses bricks. There are several innovate reasons for this.
- The front hood is also made out of steel and integrated into the front design allowing the smoke to be directed into the chimney.
- The weight of the steel front, hood, chimney and door is vertical down and rests on the steel plate of the front of the oven which rests on the concrete base.
- This allows for a hinged stainless steel insulated door, which seals directly to the front steel plate of the oven allowing an airtight seal during the baking cycles.
- The ash slot as well as the door's arch support is also integrated into the front steel plate structure of the oven, this satisfies structural engineering points and ease of cleaning of the ashes.
- The hood of the oven does not require any side supports, like it would with a brick oven front. Therefore the door can swing all the way out of the way to one side, which allows unhindered access to the oven's interior, appreciated especially when it is close to eight feet to the back of the oven. Remember, to the back of the baking chamber is about eight feet and therefore the ash scraper or the oven peel needs to be approximately 10 feet in total length.
- Fresh air is drawn into the oven along the sole of the oven via the door and the ash slot to supply oxygen to feed the fire. Combustion takes place and the fumes (smoke) rise to the roof of the oven and exits via the chimney, this creates a draft ( just like in a wood stove in house) and is proportional to the height of the chimney. The ideal situation is that there is enough draft to ensure a controlled oxygen supply for the fire to burn, the heat from the fire is absorbed into the masonry, and the smoke is completely removed out of the chimney (due to proper hood design), and completely burn so that only minimal ashes need to be removed after the oven's heating cycle.
- A damper installed at the top of the hood where the chimney starts allows for micro adjustment of the inner air pressures, if required, which are influenced by external atmospheric pressure differences.
- Length, width and height of the baking chamber is also proportional to assure good air circulation as well as maximizing the radiant heat absorption of the fire.
- By doubling and tripling the layers of the fire bricks of the bottom, top, and sides, the mass of the oven is substantially increased, which proportionally increases the oven's heat retention, which is utilized for subsequent baking.
- Following the above feature, generous insulation likewise allows for the stored heat in the fire bricks to be retained for an extended long time, just like in a well-insulated house.
- A steel I-beam harness acting like a corset around the inner fire brick-walls ensures stability of the arch and helps to keep everything in place for the longevity of the oven. Making the oven earthquake proof.
- There are three temperature probes built into the sole and three into the vault of the oven, which connect to a digital temperature meter. This way the heating of the bricks can be monitored and the fire on the inside of the oven moved around to achieve the best uniform heat throughout the baking chamber. With experience it also allows you to gauge how much wood will be required to bring the oven up to temperature.
I took many pictures during the construction of the oven, leaving a trail for anyone that wishes to follow, possibly make more improvements on the oven. This project documents my thoughts and experiences, which allowed me to also set some of the guiding principles I believe in, into stone for others and the next generation of sourdough bakers.
After construction, I fired the oven many times spanning over several week period; first small fires and slowly increasing it to remove all of the excess moisture in the brick work and the insulation, like a curing or burn-in time.
In the spring and throughout the summer of 2012, we'll bake in the oven and compare the results to see what and if there is a difference between the more modern stone deck ovens we regularly use in the Kaslo Sourdough Bakery.
I should point out that the oven we use in our daily operation was engineered precisely for the purpose of emulating the baking characteristics of a wood fired brick oven. We will use the same dough and bake bread in the two different ovens.
In parting I would like to point out that there is a difference between a wood fired brick oven for bread and one for pizza. A pizza requires baking for a relatively short time and somewhat hotter; therefore sometimes the fire is even left in the oven. The masonry is usually much less in mass compared to a bread oven. You can use a bread oven to bake pizza or cook your turkey in it, but you cannot use a wood fired pizza oven for baking bread, especially if it is sourdough bread. The extended time to bake the bread thoroughly is just not there and you'll get undercooked bread.
Have fun, whatever you do and plan ahead and gather as much information before you build an oven like this, identify size and intended purpose.