What causes cutter tops to turn brown?

[Bluefish]

It was happening on my 357xp, curious as to why? Thanks, Russ

 

[Gologit]

Wet wood getting hot, cooking and caking on? Can you scrape it off or is it the metal itself turning brown?

 

[homemade]

had that problem with my husky 460. ended up that the oil line between the tank and the bar had junk in it. lack o' oil. had to throw away two chains because they too hot and wouldn't stay sharp for nothing. And i noticed it more in dry wood then wet wood. but then again I could have been in my head the the wet wood would "scrub" the chain better then dry wood that would "bake" on the chain.

 

[Tree Feller]

The chain is getting hot, due to either lack of oil, hard wood or dull chain! Seen it before if your not careful you can ruin a chain as posted above!