Varying dramatically in size and shape, the most common Microwave Oven Transformers (MOT's) develop 2500VAC on the secondary winding when fed with 120VAC 60Hz. Secondary current can go as high as a few Amperes, while primary currents can lick up past 50A.

In the pictures above, the secondary winding (the high voltage winding) is being touched to ground, producing a very powerful arc. Looking more like a flame than anything else, the arc is extremely bright - definately something you don't want to look at without welding goggles.

The high current flowing through the discharge creates extremely high temperatures, which will melt and then vaporize just about anything, including metal. The color of the arc will change based on different substances burning in the arc itself. Aluminum burns a very intense blue color (indicating a lot of ultraviolet), and copper burns green. Steel is slightly yellowish. If the arc is drawn off of of salt, a very rich orange color is emitted because of the sodium content. Sodium HID (High Intensity Discharge) steetlamps are known for this orangish color...they are that color because there's current flowing through vaporized sodium in the bulb! So basically, drawing an arc off of salt is making a very crude sodium lamp. It sure seems to be bright enough.