This is what I believe, and no one else has to.
Energy loosens the bolts in the truss.
Energy absorbed into the bird cage wires allows reforming to more stable variants.
I believe light can change colors.
Now there is a middle ground here as well.
There are fish that when caught are fantastically brilliant in color, and begin fading as soon as they reach the surface.
There are polymorphs that are short lived as well.
I have done experiments where the end product slowly transformed into a different polymorph at room temp, in ambient light. We would Mass spec the compound as soon as created, and by an hour later, they reverted to another form.
Sometimes they were formed in some pretty harsh environments.
No one has ever explained why iron compounds can't do the same thing. Some Lead and Tin compounds do absolutely.
So, the middle of the road can say right after quench all the unstable compounds head toward the gate, and by the time they are delivered, the overall color of the piece has morphed to a "relatively stable state".
But not quite the same as when first removed from the quench.
Bill- until we can go back in time, we can't really say that we know for sure they look the same as when made.
Reminds me of the carrot colored family, it happened so gradually they never noticed they were turning orange due to some weird nutrient absorption thing.
And really, everything is headed toward entropy.
It can't be a coincidence that a man posted here that he had to recolor display pieces because of light damage. Maybe the polymorphs of that company's color process are light unstable, and other companies conditions of coloring make their's not light sensitive.
Myself, I wouldn't mind if some of that turquoise crap turned Ithaca robin's egg blue after a time.
