I. About electric discharge machining

"II. How to set machining conditions"

"III. How to design electrodes"

10. Dielectrics 

EDM is done in a machining liquid.
Without a machining liquid, machining does not make progress because molten part of the workpiece cannot be scattered by sparks.

Machining liquid used for sinker EDM is an oil which is a kind of petroleum and is near to kerosene. Kerosene also can be used, but because of the risk of fire, its flash point is raised to about 100 degrees C from about 50 degrees C which is the level of kerosene. Recently, oil-based synthetic machining liquid without harmful aromatic constituents also is used generally.

Dielectrics are sold by oil companies.