Castable resin residue

I have a application where I need to burn out castable resin that is covered in a thick copper coating. I am following the burn out schedule to the letter but I am left with thick black deposits & scale. The only aspect of the schedule I could not follow to the letter was the ramp down from 732 to 482. The furnace would not cool 111 an hour so it was left to cool overnight. Could this be the issue? I also noticed that the secondary thermocouple I placed on the part only reached 723 during 3 hour hold at 732. I am expecting the answer is the carbon was not converted while at the hold stage but I find it hard to believe the slightly lower temp of 723 would impact on that. Do I need to feed air into the furnace perhaps?

Any ideas or anyone had similar problems with residue scale?



Problem resolved. It was copper oxide scale.