A special type of carbon black produced by pyrolysis of gaseous hydrocarbons in a preheated chamber in the absence of air. Thermal black consists of relatively large individual spheres (100-500 nm diameter) and aggregates of a small number of pseudospherical particles. The preferred alignment of the layer planes is parallel to the surface of the spheres.
PAC, 1995, 67, 473. 'Recommended terminology for the description of carbon as a solid (IUPAC Recommendations 1995)' on page 505 (https://doi.org/10.1351/pac199567030473)