Black is a good emitter of infrared radiation

In theory, we have learned that

Dull (matt/rough) and black surface is a good emitter and good absorber of infrared radiation.

In this simple demonstration, the container sides are painted white matt, silver smooth and black matt.

Hot water is poured into the container and the thermal energy is conducted to the whole container. The temperature of the container is more or less uniform.

Using a infrared thermometer, we measure the temperature of the different surfaces.

From this simple demonstration, we can conclude that dull black surface is the best emitter of infrared radiation and smooth silver surface is the worst emitter of infrared radiation.