Heat Management – Cooking with Wood
Managing temperature in a wood-fired oven starts by establishing a target temperature. We recommend a 30 °F temperature “window” to provide a consistent cooking environment. By maintaining a consistent amount of open flame, it is easy to keep the oven temperature within your established window. We recommend a starting point of 535–565 °F.
By practicing consistent product rotation through temperature zones on the floor, your pizza/product will always cook the same way
Build your fire 12 inches (minimum) inside the oven doorway. This placement makes it much easier to reach into the oven to manage your fire or remove ash.
Caution: Do not allow the open flame into the venting area above the doorway (the metal transition leading to the flue). If flames are spilling out of the door opening, or if the oven floor temperature exceeds 850 °F, you are over firing the oven.
Building the Fire
It takes approximately 1-1/2 hours to establish a coal bed.
- Using the Particle Shovel, remove about two-thirds of the fly ash, leaving any live coals. The coals and ash will help start the new fire faster.
- Lay the initial log parallel with the dome approximately 12 inches inside doorway.
- Lay 2 or 3 pieces of wood across (perpendicular to) the first piece.
- Using a fire starter (not paper), start the fire. After the initial wood catches, it will probably take 2–3 more pieces to establish a 8–14 inch flame, which will take approximately 60–90 minutes.
Do not over fire the oven. During initial heat-up, no more than three or four pieces of wood should be added at a time. Flames spilling out of the oven are not safe!
If you need to build a coal bed in a hurry, use smaller pieces of wood and manage the fire closely. Wet wood takes longer to start burning and requires a larger coal bed to maintain the same amount of heat compared to wood with the optimum 15-20% moisture level.
Maintaining Your Fire/Temperature
After you have the floor temperature within your temperature window (use a digital temperature gauge), 535–565 °F in this example, it should take two pieces of wood about every 20 minutes to maintain a consistent cooking environment (8–14 inches of open flame working on the coal bed). Wood placed on an established coal bed will ignite immediately.
Note: A higher temperature window will require more fuel.
Excessive open flame creates too much top heat and your product will finish on the top before it is done on the bottom. Too little open flame will finish (or potentially burn) on the bottom first. For this reason, it is important to maintain a consistent flame height.
Efficient combustion is important to your fire. Place new log(s) across (perpendicular to) the last log that was placed on the coal bed to help maintain maximum combustion air.
Ventilation Management: A Safety Issue
Burning any wood product creates creosote—a flammable residue. Safe and proper flue management is the responsibility of the restaurant. Fuelwood quality, CFM (cubic feet per minute of ventilation air) and the amount of grease-laden vapors produced are all determining factors in the amount of creosote buildup, and will vary from installation to installation. The exhaust system should be inspected and cleaned per the manufacturer’s and/or local code official’s recommendations. Wood Stone recommends cleaning and inspection at least monthly on any ventilation system serving solid fuel equipment.
Wood that is not properly dried and sized is a common operational problem with solid fuel cooking equipment.
Harder, heavier wood species generally burn hotter and longer. Oak, Apple, Hickory, Pecan, and Mesquite have a very balanced open flame and produce long-lasting embers, and are well-suited for cooking in wood-fired ovens and char-broilers. Hardwoods produce more BTU/hr/pound, requiring less labor to maintain the same amount of heat.
Optimum-sized wood will have an average length of 16–18 inches and diameter of 3–5 inches (either full logs or the sides of split wood).
Lighter species burn faster and cooler, generating more open flame, thereby increasing the challenge of balancing floor temperature/ bottom heat with top heat.
Heat potential is measured in BTU/hr/pound. For example:
- A pound of wood at 15-20% moisture produces approx. 6,500 BTU/hr/pound.
- A cord (4′ x 4′ x 8′) of Oak weighs 4600 pounds, while a cord of Birch weighs 3000 pounds.
- Assuming a 15-20% moisture level, it is fairly easy to see you would need a lot more Birch to maintain the same amount of oven heat that the Oak creates.
Ideal moisture levels fall between 15–20%. If wood contains more than 20% moisture, it should not be accepted for use. Accurate moisture readings are taken from the center of a freshly split piece of wood. Wood should be stored in a covered area that allows good air circulation so the drying process can continue. (Follow the recommendations in Chapter 14 of the National Fire Protection Association Standard (NFPA 96), and/or local codes for safe wood storage and handling practices.)
Because most wood is sold for heating, it is often only cured for 4–8 months, rather than the 12–16 months required for cooking. It is important to buy wood that has been cured adequately. Indicators of high moisture content include hissing (20–25% moisture level), or bubbles forming out the end (moisture higher than 25%).
Note: Wood at higher moisture levels produces more creosote residue, which accumulates on the flue lining and exhaust hood, increasing the risk of fire.
Each species of wood has different characteristics. The table below should help weigh the pros and cons of various types of wood. Wood from conifers (pine trees) is not recommended due to its poor fuel/wood characteristics (low weight, low-med heat, poor coaling, high sparking and high residual creosote).