propeller 21 an exhaust side of the fluid jet mill 3 communicated with a circulation pipe 23 which included a valve 22 and the circulation pipe 23 further communicated with the decompression and heating treatment chamber 1 furthermore a lower side of the valve 22 of the circulation pipe 23 communicated with the powder filter 4 which included a valve 24 the powder filter 4 was a trap which communicated with an exhaust system 26 by way of a cylindrical filter 25 90 grams of the above described pearl mica pigment was supplied into the barrel 2 of the above described powder sputtering apparatus and the decompression and heating treatment chamber 1 was decompressed to 2 u00d7 10 5 torr then an argon gas was supplied gradually through a pipe 31 in order to supply the pigment into the fluid jet mill 3 after colliding the pigment with the propeller 2 so as to disperse it in its primary particles the pigment was collected in the decompression and heating treatment chamber 1 then the decompression and heating treatment chamber 1 was decompressed to 2 u00d7 10 2 torr and it was heated to 100 u00b0 c with a heater thus the collected pigment was dried and degassing was carried out for 30.