What’s this white stuff on the spark plugs?

[Aviator305]

This white residue was on all of my Champion massive spark plugs at annual. Is this lead bromide from LOP operations? These plugs were installed new after major overhaul the previous year and were not changed or cleaned for 100 hours. The first fifty hours consisted of ROP fly-it-like you-stole-it for break-in. The next 50 hours I was mostly at 55% power somewhere between peak EGT and LOP on my leanest cylinder. Everything was smooth except for mag checks on run up which corrected on the second go around from R->L and would also be mitigated by leaning to 2000RPM (set MP so that RPM would go to about 1950, and then pulled back mixture so that RPM would climb to 2000).

This is on a Lycoming O-540. The plugs were replaced at annual, so this is not an active issue for me. I am just curious as to what the white residue is and if it means anything about the way I ran my engine - good or bad.

 

[GM.]

 

[Aviator305]

 

[JohnPhillips]

 

[Aviator305]

 

[Ray93J]

 

[Orest @ CYFD]

 

[GM.]

 

[Aviator305]

 

[GM.]