Uneven Deck Oven Baking Before a School Order
A bakery has a two-deck electric oven set to 220°C for 40 lean dough loaves baked on four trays. The oven thermostat reads 220°C, but an oven thermometer placed on the top deck shows 248°C near the front and 236°C at the back; the bottom deck shows 195°C. After 25 minutes, loaves on the top deck have dark, almost burnt crusts and sticky crumb near the base; loaves on the bottom deck are pale, pale-sided and gummy in the centre. The baker opened the door at 10 minutes and again at 18 minutes to rotate trays, and loaded all four trays at once. The bakery has a busy school order and no second oven. The oven was last calibrated eight months ago. The baker wants to know whether to change the thermostat setting, the loading pattern, or both.
1. Diagnose why the two decks are producing opposite faults, referring to the temperatures, loading and door openings.
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The thermostat is not a reliable guide because the measured temperatures differ sharply from the set point: the top deck is 16–28°C above 220°C and the bottom deck is 25°C below it. The top loaves therefore receive excessive top heat: the crust sets and browns before the centre is baked, leaving a sticky base. The bottom loaves receive too little bottom heat and cannot recover oven spring, so they are pale and gummy. Loading four trays at once restricts air circulation and increases the load on the lower deck. Opening the door at 10 and 18 minutes drops the oven temperature and interrupts oven spring; the top deck may then over-brown when the thermostat calls for heat again. This is a heat-distribution and verification problem, not a single 'wrong temperature' problem. Changing only the thermostat would still leave a 40–50°C difference between decks.
2. Recommend a practical baking plan for the next order, including oven setting, loading, rotation and when to open the door.
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Preheat for at least 30 minutes and verify with the oven thermometer, not the dial. Set the oven lower, around 200–205°C, and bake one tray per deck if tray size allows; if four trays are essential, use two trays per deck with space between them and avoid covering the whole deck. Load the cooler bottom deck first or give it 5 minutes' head start. Do not open the door before 15–18 minutes; rotate once only, quickly, and close the door firmly. If the top deck still runs hot, use a lower top heat or a baking sheet above the loaves as a shield, and move loaves to the bottom deck for the last 5 minutes if colour is ahead of crumb. Bake to internal doneness or a hollow base sound, not only to 25 minutes. Record the actual thermometer readings and the result so the next batch is not guesswork.
3. Explain how the bakery should verify and maintain the oven after this order, and what records to keep.
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After production, cool the oven and check the thermostat against a calibrated oven thermometer at three points on each deck: front, centre and back. If the difference exceeds about 10°C from the set point, call a technician to recalibrate or replace the thermostat or element. Clean the door seal and check that it closes evenly; a poor seal causes heat loss and uneven baking. Record the date, set temperature, measured temperatures at each point, any repairs, and the baking result for a test tray of three loaves. Repeat the check monthly and after any repair. Keep the thermometer in the bakery, not locked in an office. For the school order, do not promise a delivery time until a test tray on each deck has been baked and judged. This turns a one-off crisis into a simple preventive-maintenance routine that a small bakery can sustain.