PURPOSE : To perform clear jet printing on a surface of an article having high surface temperature, i.e., from 80 to 140癈. CONSTITUTION : A prescribed amount of illuminating kerosine having a high boiling point, i.e., from 160 to 250癈, is incorporated into a solvent of a rubber- base coating material. Thus, even when droplets of the coating material sprayed toward an article pass through a high-temperature atmosphere around the article, the solvent in the droplets will not evaporate much and, as a result, the droplets will spread out when they strike against the surface of the article so that large and clear printed characters can be obtained.