How to create an enamelled cast iron shader in Blender? I am trying to create a round cocotte as in the image below.



This cocotte is enamelled cast iron. And my question is about how to recreate the enamelled cast iron in blender. 


  Traditional enamelling in simple terms is the fusing of tiny glass
  particles with heat to form a solid layer of colour onto a metal
  background.  It can be matt, shiny, opaque or translucent, and comes
  in a wide selection of colours and finishes.


I have now a very first model and I am in the process of recreating this enamelled cast iron in blender. I first want to know if this works before I continue.

I have created a mix shader. Mixing a principled shader with the cast iron (including roughness) and a principled shader for the color. This is the result. 



As you can see the red colored surface has the same surface structure/roughnes as the cast iron. But that is not what you can see at the image of the real cocotte. That is because the melted glass is a sort of coating on the cast iron. This coating has sort of a smooth, wavy surface.

How to give this red enamelled glass coating the smooth, wavy surface ? I don't think I can do that with changing the roughness of the cast iron. I now think I shouldn't use the cast iron textures. Because the color will always get the surface of the cast iron and that is not what I want.

I think I should create a material that gives that lumpy, wavy surface as you can see in the image of the original cocotte. How to create such a surface ? A sort of wavy, gloopy surface....
Artistic approach using noise and principled bsdf 



I'd use a principled shader along with a specular value of 1 and a roughness value of 0.3 to get the surface appearence of iron. You can break the rules and raise up the clearcoat value to 2 or even higher in order to match the shininess/coating of the reference. For each type of surface bump, you can combine different 3d noises and feed them into the normal socket of a principled shader. I'd also add some color variation to the base color using noise again: