I dont have pics..But, detonation or pinging removes tinsy specs of piston when it occurs. They get deposited on the porcelain, and you can see tiny silver flecks. (hence the light and magnifier) Oil will show similar to fuel, but be more black an din extreme cases, wet. It also builds up much faster than ncarbon, so if you look down in the recess between the porcelain and body, you'll see it looking like black mud down in there. Lean will keep the plugs looking brand new. Once it's been run, you should see light deposits (brownish or greyish depending on fuel) on the ceramic. Where they appear in terms of hieght can tell you if it's close but lean. The heat will discolor the steel body inside by the porcelain in a ring. If that's right up near the edge, that may mean your timing is retarded, or your octane may be too high. Conversly, a ring a tthe tip, or on the ground electrode can mean too advanced or not enough octane. The down side..Any time spent at idle, or issues like having to pump the gas when starting, can ruin the "blank slate" of a new plug. Many racers I know pop a brandi new one in, makew a pass, shut it off and coast off the track, then pull it on the return road to avoid any "contamination". I run NGK Race plugs because they are easier to read for me. You will find different manufacturers will "stain" and color differently too. I hate Bosch..lol. There's guys that have years of doing this, and they can tune beter than an LM1 and a chassis dyno..lol.
