I just purchased MCB WHITE FERRULE ROD. so that I could make my own ferrules. I just made & installed one on one of my shafts. but there seems to be one or 2 dark spots on the ferrule after I turned it down. seems like they are dark spots that were inside the ferrule rod. is this normal? if not what can I do to remove them or conceal them. I dont want to say where I purchased the rod. I dont want to start bashing before I know what is expected of MCB.