The next stage in the painting was to add some variations to the colour of the rust. I mixed up some cadmium orange oil paint and started work.The oil paints I have are ancient. They still work great though, even if I do have to use a wrench to get some of the caps off! The more orange rust is fresh, so I added it mainly on edges, leaving the centres of the rust patches the darker burnt sienna. I just dabbed on the tiniest of dots of the orange, and it spreads nicely into the already dry base coat of oil paint. If the orange is too strong, a cotton bud can take it off again, or you can add in dabs of the burnt sienna.  The orange can also be used as a wash to just subtly alter the colour of a flat area. I tried to add orange to some of the areas which had received the under-painted chips and not been heavily chipped with the oily steel. The canisters and pipe that go on the large side pieces weathered up nicely. I also used some burnt umber oil paint to make some dark (but not black) details. Burnt umber is very similar to the burnt sienna, but it’s a much darker brown whereas the burnt sienna still has a fair bit of redness in it. They’re both based primarily on iron oxide making them perfect for rust. The subtle hints of orange help spread the rusted areas without them obliterating the blue paint. For the metal part of the gun barrel I dropped in burnt umber to darken down the recessed areas. Previously this arm wasn’t too rusty, but looking at the under-painted chips, it should be starting to rust, so now we see the orange coming through, with some darker burnt sienna where the rust has really taken hold. I did a lot of work on these main side pieces. They have large areas where there’s mild under-painted chips so I carefully toned them orange, and kept the stronger dark-brown rust in the deepest areas. Looking at this photo I’m not happy with the blue part above where the wheels attached, so I’m working now on really making that a solid area of dirty rust.