Sure it’s terrifying, but you can start a sparky plasma show in a resilient enough container and keep it going for hours and the microwave won’t break. (except maybe overheat.) The microwave will be fine as long as the arcs don’t reach the waveguide cover. (which would risk burning/shorting the magnetron.)
I have done the microwave grape plasma trick myself and started an arc in a microwave. The current between the two objects goes through a very narrow point, which is enough vaporize the contact point to plasma. This then can grow as the microwave continues to pump more energy into the spark.
Sure it’s terrifying, but you can start a sparky plasma show in a resilient enough container and keep it going for hours and the microwave won’t break. (except maybe overheat.) The microwave will be fine as long as the arcs don’t reach the waveguide cover. (which would risk burning/shorting the magnetron.)
I have done the microwave grape plasma trick myself and started an arc in a microwave. The current between the two objects goes through a very narrow point, which is enough vaporize the contact point to plasma. This then can grow as the microwave continues to pump more energy into the spark.