Material "ChrisP Copper Manual"

Use this node group for full control over the copper material's properties.

Copper Color Age
A slider from brand new copper to aged, green copper

Copper  Hue Saturation Brightness
Easily adjust or completely alter the color palette of the metal material

Copper Color Variation
0 (default) gives normal color variations, -1 is no color variations, +1 is very pronounced color variations

Copper Oil Amount
Add colorful "rainbow" variations in the reflections

Copper Roughness + Variation
Set the overall roughness and add some roughness variation

Patina
Plug in an image map or vertex colors to define the areas of the patina and set the patina amount
Quick-Tip: "Dirty Vertex Colors" (see video!)

Dust
Dust can easily be applied to all the faces pointing upwards (Z-axis) and visually behaves like in the real-world: Dust is more visible when viewed at an angle and less visible when looked at straight on

The "Scale" properties can be used to adjust the scale of the procedural textures to fit your model/scene.

Custom Normals (e.g. bump/normal map) can be added

BONUS Material "ChrisP Copper Auto"

Use this node group for the quickest way to realistic copper.

Age

Changing this single value will adjust all of the other parameters  automatically for perfect results.

Scale 
can be used to adjust the scale of the procedural textures to fit your model/scene

Hue Saturation Brightness, Patina, Dust, Normal
same as "ChrisP Copper Manual"

BONUS Material "ChrisP AddDust"

This node can be used with any material setup to quickly and realisticly put dust on top of any object.
The dust will be more prominent when viewed at an angle and less so when looked straight on.
This should be the last node in a node tree right before the Material Output.