When starting the initial fire in the oven be sure to keep the oven door and chimney open to increase the amount of oxygen available to the fire. Begin by scrunching news paper into balls and placing them into the center of the wood fired pizza oven. Stack small pieces of wood (sticks smaller the diameter of your pinkie finger or 1 cm in diameter) around the paper like a tent or tepee. Place some slightly larger pieces of wood over these (2cm diameter). Light this fire and gradually add larger pieces (3cm diameter) of wood to the fire over a 1 hour period. Initially at the outset of creating the fire there is a period where excess smoke may be produced. This is normal and will diminish as heat builds. Begin by using thin and dry wood, and blow air into the oven to quickly build the heat. Once sufficient heat is being generated the gasses given off by the wood will ignite rather than smoke. If the flue and chimney are correctly placed on the outside of the oven in front of the door this smoke will generally not be an issue. You may wish to invest in an oven thermometer to gauge the temperature generated. Ideally for pizza you will want to establish a temperature of at least 370 degrees Celsius (700 degrees Fahrenheit) to allow for pizzas to be cooked within 1-2 minutes.
You can judge the temperature of a wood fired oven either through a mechanical thermometer, a digital thermometer, or a technique using regular flour. To gauge if the oven is ready to cook pizza you can throw some flour directly into the oven. Ideally it will turn golden brown and then gradually darken. If this is adequately fast but not too quick the oven is ready. If the flour remains white or only slowly turns yellow the oven is not ready. Pizza needs a very hot oven in order to crisp the bottom rather than turn soggy. If the flour turns black fast the oven is too hot and you should resist adding more wood to the fire to allow the heat to reduce.
Once the oven has reached the desired temperature look to either smother or control the fire to a manageable size. Once the fire is controlled, sweep the hearth of the oven to remove wood ash. The oven door and chimney should be closed so as to prevent unnecessary release of heat. Leave the oven sit for 5 minutes to allow the heat to evenly distribute. If this is not done it is likely that hot spots will be present within the oven which will lead to the pizza or other foods cooking unevenly. Once the oven temperature has dropped slightly, has stabilised and is evenly distributed, the first pizza may be inserted.
If foods other than bread such as pizza, roasts, casseroles, or pies are initially being cooked, it is usually necessary to maintain a small steady fire at the back of the oven. When cooking pizza the oven door should remain open, and the temperature will want to be up around 425°C (800°F) so as to cook the pizza in only 90 seconds. For other food the oven temperature can be maintained at a more stable rate by closing the door.
For breads it is advised that the fire be extinguished so that only hot embers remain. These embers can be either evenly distributed around the walls of the oven or remove entirely into an aluminium bucket. Be sure to be safety conscious as obviously this is very dangerous. Removed embers should be doused with water so as to prevent injury.
As pizza ovens are very efficient at capturing heat and then radiating it effectively over a period of time, the cooking duration can be very long. For small ovens this might be 2 hours, however for large ovens it might be over 24 hours. The duration that the oven remains hot will be dependent upon the size, shape, insulating material and initial temperature reached. Because the heat is radiating from every part of a wood fired oven, the evenness of cooking may be much better than with standard conventional ovens. Conversely because gas and electric ovens have a single heat source the distribution is not even. Due to the long cooking duration and ability to retain heat these ovens have traditionally been used for many purposes including drying fruits, herbs, mushrooms or drying wood for the next firing.
The mass of the oven is generally the most important factor in determining the maximum temperature and duration of cooking ability. For this reason is it conventional to place a thick layer of oven thermal insulation to increase the ability to absorb and then radiate heat. For most ovens it is suggested that this insulation layer be placed oven the dome whether constructed of fire brick or cob. If it is discovered that the oven is not performing as desired once construction has finished, a further layer of insulation or cladding of 5 cm (2 inches) should be applied at a minimum.
Wood used to build the fire should be hard and dry. Avoid wet or green wood as this will not readily burn and will create excess smoke. Choose small pieces to begin the fire and gradually move up to larger pieces as the heat intensifies. Do not use wood made for construction. Wood from construction or buildings may have been treated to prevent rot or termites and as such may contain harmful chemicals such as chlorine, arsenic, copper, and chromium. Never burn wood that contains or is coated in paint as again this may cause hazardous smoke and fumes.