No, it is not safe to microwave a damp sponge for cleaning purposes. Microwaving a damp sponge can create a potentially hazardous situation due to the combination of heat, moisture, and the material of the sponge.
When you heat a damp sponge in a microwave, the water inside the sponge can quickly become superheated. Superheated water can reach temperatures above its boiling point without actually boiling. This means that when you remove the sponge from the microwave, any slight disturbance or contact with an object can cause the water to rapidly boil, resulting in a sudden release of steam. This can lead to burns and scalds if you come into contact with the hot steam or water.
Furthermore, microwaving sponges can also be a fire hazard. Some sponges contain synthetic materials or metallic components that can heat up rapidly and potentially ignite or cause damage to the microwave.
To clean a sponge effectively, it's generally recommended to use other methods such as soaking it in soapy water, washing it in a dishwasher (if it is dishwasher-safe), or replacing it with a new one when it becomes worn or dirty.