A printing ink includes a micrometer-sized or nanometer-sized coal material. The micrometer-sized or nanometer-sized coal material is produced using a method of providing a controlled batch of micrometer-sized or nanometer-sized coal material. This method includes the steps of: (a) specifying at least one desired physical and/or chemical parameter of the controlled batch of coal material; (b) specifying the desired range of the physical and/or chemical parameter in the controlled batch of coal material; (c) obtaining a feedstock batch of coal material; and (d) processing a feedstock batch of coal material to obtain the controlled batch of coal material having the at least one specified physical and/or chemical parameter in the specified range thereof. In a further step, the controlled batch of coal material can be activated.