Encapsulated particulate magnetic development powders containing a sublimable dyestuff

Dry and free flowing electro-photographic development or toner powder of essentially spherical particles which have a diameter between about 5.mu. and about 50.mu., said particles comprising an organic binder, ferromagnetic material, highly conducting carbon particles, a surface active compound, and a dyestuff which is adapted to evaporate from said particles in one minute at atmospheric pressure and a temperature between about 140 degrees C. and about 220 degrees C., wherein said dyestuff is present in an amount of at least 5% by weight of said powder and said surfactant is present in an amount of at least 4% by weight of said powder, and further wherein substantially each of said particles of said powder consists of two different solid phases in which the inner nucleus phase is surrounded by an outside shell phase, said inner nucleus phase comprising a first organic binder which is essentially void of ferromagnetic material, with 10% to 75% by weight of said inner nucleus phase consisting of said dyestuff and 4% to 20% by weight of said inner nucleus phase consisting of said surfactant, said outer shell phase, which is essentially void of dyestuff, comprising a second organic binder, with 30% to 80% by weight of said outer shell phase consisting of small particles of said ferromagnetic material and 2% to 20% by weight of said outer shell phase consisting of small particles of said highly conducting carbon.