When a small weight is placed on the pressure cooker's pressure regulator or valve, it increases the pressure of the steam in the area of contact. This is due to the increase in pressure exerted by the weight on the valve, which restricts the escape of steam and reduces the rate at which steam is released from the cooker.
To understand this better, let's consider the working principle of a pressure cooker:
Pressure Building Stage: As the liquid inside the pressure cooker is heated, it generates steam, which increases the pressure inside the sealed pot. The pressure regulator or valve on the lid is designed to allow excess steam to escape. In the initial stages of heating, the pressure regulator remains open, and steam escapes continuously through the steam vent.
Controlling Pressure: The pressure regulator is typically a weighted valve or a spring-loaded valve. It is designed to respond to the pressure inside the cooker. When the pressure inside the cooker reaches a specific level, the regulator senses this pressure and reacts accordingly.
Weighted Pressure Regulator: In a pressure cooker with a weighted pressure regulator, the regulator consists of a small weight that sits on top of the valve. This weight is calibrated to provide a specific pressure setting. As the steam pressure inside the cooker increases during the cooking process, it pushes against the pressure regulator's weight.
Increasing Pressure at the Area of Contact: When the small weight is placed on the pressure regulator, it adds an additional downward force on the valve. This increases the overall pressure needed to lift the valve and release steam through the vent. As a result, the pressure in the area of contact between the valve and its seat is increased, effectively making it more challenging for the steam to escape.
Pressure Retention: The increased pressure in the area of contact between the valve and its seat caused by the added weight results in better sealing of the valve. This, in turn, helps to retain more steam inside the cooker, leading to a higher internal pressure and temperature.
By adjusting the weight on the pressure regulator, you can control the pressure level inside the pressure cooker. Higher weights will increase the pressure setting, while lighter weights or no weight at all will allow for a lower pressure setting.
It's important to note that altering the weight on the pressure regulator should be done with caution and according to the manufacturer's guidelines to ensure safe and effective operation of the pressure cooker. Proper pressure control is essential for cooking food safely and efficiently in a pressure cooker.