In most roasters, the amount of heat transferred by radiation is negligible (Schenker and Rothgeb 2017). Most roasters described as ‘infrared’ use infrared burners (see Lesson 1.02) but do not transmit any of that infrared radiation to the beans directly. Instead, the radiation heats the surrounding air, the drum, and in some cases, heat exchangers around the drum. From there, the heat travels to the beans via conduction and convection. Infrared radiation can’t penetrate the drum unless it is perforated.
Some manufacturers, such as Rubasse, have built small roasters that use infrared radiation as a primary heat source, with the heating elements placed inside the drum so that the infrared radiation can reach the beans.