by Andrew » Wed Nov 09, 2022 1:59 pm
Thanks for the kind comments, they're very much appreciated.
I think I have waffled on about rusting techniques before, but this thread now runs to over 50 pages and spans a decade, so I wouldn't expect to read back through it!
Essentially, they're a synthesis of techniques borrowed from others (including some on here), that I've evolved to meet my own needs.
The basic ingredient is iron powder, seeming sold mostly for science experiments in schools. Ideally, you want nice fine stuff - I experimented with courser filings and was disappointed with the result.
I paint (and letter) the body, let it dry, then apply more paint just where I want the rust to be - looking at pictures of the real thing is best, but I tend to go for where water would collect or paint would be damaged.
While that paint's still wet, I apply the powder (pretty liberally) from an old Lidl container that originally dispensed peppercorns, using the same technique that Blue Peter presenters use to apply glitter to cardboard boxes, over a sheet of newspaper so that any excess that doesn't stick can be poured back into the pot.
Once that's dry, and where it seems appropriate, I use the body colour to paint over the powder for a couple of millimetres around the edge of each rust patch - the idea is that once the powder turns to rust, it'll look like it's eating away beneath the paint too. It also helps soften the edges of the rust patches - if you look closely, some of mine end a little abruptly, which doesn't look right. It's possible I need to extend those "transition zones", maybe up to say 5mm in places.
After all of that, it's time to "activate" the rust. I've used two techniques, one involving vinegar, the other copper suplhate solution. Again, the latter is sold for schools, but send me a message if you'd like some, a little goes a very long way, and I seem to have a lifetime's worth! Either way, you can spray it on with an old spray bottle or apply with a brush.
I've no idea what the chemistry behind it is, but my experience is that vinegar produces older looking black/brown rust, whereas copper sulphate makes very new looking bright orange rust. I've not tried it (I should), but I'm guessing that different concentrates of the the solution would yield different results. Vinegar takes longer to act, and can be sped up a little by leaving the model in a steamy bathroom or similar, and the dark brown rust can be enlivened a little by rubbing with wire wool.
I think I'm going to stick with copper sulphate in future - it's quick and reliable, and although the rust is rather too startlingly orange for most applications (again, experimentation with concentration is called for...), that can be toned down - that's the next stage...
Next, it's on to general weathering. I usually start with a wash of dilute black or dark grey paint, slightly more concentrated for a coal wagon. I use acrylics for painting wagons, so add a drop of washing up liquid to help it get into the nooks and crannies. Then I wipe it off again with a down (ie rain)-ward motion of a dry cloth - it remains in the aforementioned crannies. Then, I add a gunky brown wash to the lower bits of the wagon, wiping upwards to represent dirt splashed up by rain, or from the wheels. Those washes will permeate the rust (whether you want them to or not, to an extent!), toning down the colour, and this can be adapted to suit your requirements.
I generally replicate less established rust (just a general rusty patina) by dry brushing, again downwards, using a palette of orange and brown acrylics. This looks especially good around rivet detail etc, although it occasionally, and annoyingly, it dislodges them! Where I've got a patch of "real" rust, the same technique can be used to represent rain streaking - I think that went pretty well on the coal wagon. I'm quite careful to mix a good approximation of the colour of the patch, which then gets a little more orangey as it runs down the wagon - that seems to be how the real thing looks.
And that's it. Practice makes perfect - I'm a long way from there, but I'm getting better!
PS I'll try to illustrate the above with pictures some time...