A while back I cleaned the brand new ninja's from Ball Baron with alcohol and wiped them clean. Within an hour I started to see oxidation on the pinballs and they looked really bad. Took them out and cleaned them again with the alcohol thinking I must have missed something and they did it again. On the third try I just sprayed them with sprayaway (my favorite glass cleaner) and they have been fine ever sense. I no longer use the alcohol and just clean with the glass cleaner.