PURPOSE: To elongate the period of acetylene generation, by adding calcium carbide to an oil or fat, polymerizing and oxidizing the unsaturated fatty acids in the oil or fat, and covering the carbide with the oxidized oil or fat.

CONSTITUTION: An oil or fat such as drying oil, semidrying oil, etc. is heated at about its boiling point, mixed with calcium carbide, stirred at the temperature, and then made to contact with air to polymerize and oxidize the unsaturated fatty acids contained in the oil or fat. The oil or fat is degraded and its viscosity is remarkably increased by the treatment, and accordingly, the carbide particles are covered with a relatively thick coating film. The reaction period of the carbon particle with water can be controlled with the amount of oil attached to the surface, and the acetylene generation period can be controlled. The oil- coated carbide particles obtained by the process can be used also as an excellent flower-bud inducing agent.