Polybook Morten Fjellheim (Arev)

Hey Arev! Grats on the polybook.  The lamp looks good! Here are a few suggestions I have: 

1) I am not sure why you need the second principled shader.  I feel like this destructive as it wipes out 50% of the info you put into the first one.  I assume it is being used to add color (since it looks like you are using grayscale inputs for the first one)? I would try to map the color info into the first principled using some mix RGB setup so you don’t lose bump and roughness information.

2) You might try using a curvature or AO map to mask your rust texture (assuming it’s rust?) so that it looks like it conforms to your model and less like a foreign texture map.  Also make sure scale is applied and that your UV islands are in proportion.  The rust splotches at the bottom look much bigger than those elsewhere on the lamp.

3) The glass is very saturated, which I like actually. It makes look like its old, cloudy, and grimey, but the flame still appears crystal clear through it.  Maybe break it up a bit and put some burn marks around the bottom and grime up that really shiny metal base so it fits in better.

All in all, nice render though.  Look forward to seeing more!

What I am saying is that it appears you are trying to create two different materials (with different values each for color/roughness/metalness), but nothing is plugged in to the factor of your mix node.  So it renders a 50/50 mix of the properties for both principled shaders. I do not think this is what you want.  You want some areas that are 100% rust and some that are 100% metal.  You need to create some kind of mask to differentiate (plugging your image into a high contrast color ramp could give you this for free).  You could then plug that mask into a mix shader factor or just plug it into your various value slots on a single principled shader.

There are two images, one is plugged into a color ramp (such that the output is grayscale) and the other appears to be a height map (these are usually grayscale).  But you could use a mix RGB with your material mask to plug colors into the color slot on a single principled shader rather than have two.

For the splotches, yes I am referring to their size.  I cannot see the image texture, but because the splotch size varies substantially between different parts of the mesh, I believe there is some kind of scaling issue, either on the mesh itself or with the UVs.  Fixing that would distribute the rust a bit more evenly.

Finally, if you combined the material mask with a curvature or AO map, the rust sections could be mapped to specific places on your model where moisture would be likely to accrue, rather than be governed by an image that probably was not designed with your lamp in mind.

Looking good Morten! 2 ideas that may help.
1) I would reduce the strength of the bump by at least 50%.
2) I would add a metallic layer to the material that goes between the paint and rust. I think that will help sell it as rust so that we can see where the paint has chipped away and exposed the metal and then the metal has rusted in places.