Thank you for the step by step footage. Let me just get this straight... You first started with a rough color sketch (did you start directly with the paint without linework?) Then you increased the details, still by painting it. In picture 5 the details increase a lot. Did you use photos for the textures?
Hi akleinma: Thanks for your words! Yes, this started out with just a simple blockin of values..I had the "final image in mind" but experimented a lot with the composition etc. Sometimes I don't have an image in my head at all, and it just comes out of the first few strokes.
In the 5th step I added a parts of an old painting, and also some textures of pipes (seemed appropriate) but not so much for the pipes themselves, but more so to break up values and create a bit new colors. Also a "rust" texture was applied over the whole image several times and on different layer modes to create new colors/values/detail etc. I hope that makes things a bit more clear! Next time i'll try to write a bit more indepth about my process!