So I’ve been making jigs for a few years now and from time to time, some type of residue stains my jig heads after I cure them in my toaster oven. It seems that you can only see it on the white or lighter colored jig heads. I first started noticing the residue in the racks in the toaster oven. Thought it was rust at first so I bought a new toaster oven, but the first time I used the new one the same thing happened. All of the hooks I use are black nickel finish. Could that finish be melting off in my toaster oven? If so, am I getting it too hot? I usually bake my heads for 25 minutes on 350 degrees.