The first heating of the tandoor should result from the readiness of the entire structure. There is no single number of days that describes every cross-section, weather condition, and material set. Before preparing the fuel, collect the dates of wet work and requirements for all completed layers.
Setting and drying are different stages
Outdoor Oven Cement sets hydraulically in compatible applications. Fire is not needed for this process itself. However, curing the joint does not automatically confirm that the entire chamber is dry and ready for intensive operation.
Heatproof Screed has its own preparation, setting and drying conditions. Also check the bricks, insulation, and exterior finish. The last applied wet layer may affect the readiness timing of the other parts.
Assess the actual construction conditions
Inspect the base, entrance, and areas shielded from drafts. Water may enter the furnace from precipitation or neighboring layers. A longer pause does not guarantee drying if the source of moisture remains active.
Firebricks and their joints should maintain the required support. Check the condition before starting the planned heating and take photos. Do not confirm the correctness of execution by suddenly increasing the heat in a damp chamber.
Record the stages instead of guaranteeing the absence of cracks
Record the preparation carried out, weather conditions, and heating method according to the instructions. After cooling, compare the entrance, joints and supports. The record of new cracks should include their location and changes relative to the previous state.
If movement or separation occurs, determine the cause before the next use. The proper preparation sequence reduces risks related to moisture, but it does not guarantee a structure without any cracks. Documentation will facilitate later assessment of materials and execution, rather than attributing every change to a single random stage.