If you use the silver or black high temp paint (I have used both in the past) you will notice you have to break the bond with a copper or plastic hammer next time you split heads... It gives a really good bond/seal...
And this is what happens if you don't check your head bolts often enough on a supercharged engine, our last pass at Bonneville in 2013, one got loose and the flame front went past it melting some alloy in the process:
Patrick