well I have to disagree, I have a little spark plug cleaner and it works!, you simply sandblast the plugs and then regap them and they are as good as new, only thing you have to do is blow them out very well with air when done, and then inspect to make sure none of the blasting agent is left in the plug. Its a relatively cheap cleaner like $20. Send me all your old plugs if you think they cant work like new...
You see when you "foul" a plug ,what has happened is fuel/oil has gotten up between the insulator cone and the grounding shield or metal base, electricity takes the path of least resistance so instead of traveling down the electrode and thru the cone, to the grounding strap, it jumps off the side to ground. When you use this little cleaner, it removes the deposits and restores the plugs performance to like new. I have done this for years and years and have yet to have one fail any differnt then a new one does. Plugs do sometimes go bad, the porcelin cracks, the electrode becomes rounded, this doesnt fix that only "fouled plugs"