A method of applying a coating to a spark plug insulator comprises the steps of forming a slurry solution and applying the slurry solution as a first coating to an insulative sleeve configured for use in a spark plug. The method further includes the step of heat treating the insulative sleeve to a temperature of between about 500 degrees Celsius and about 1000 degrees Celsius for between about 10 minutes and about 2 hour(s). Still further, the method includes the step of applying a second coating overlying at least a portion of the first coating, wherein the second coating comprises an organic binder.