This article describes the process of weathering locomotives, including steam, diesel and electric motive power.
Locomotives probably offer the best opportunities for weathering, particularly those representing the end of the steam era, because any level of weathering is possible - anything from a 'light dusting' to the 'full works'.
The methods used vary according to the level of weathering. It is usually a good idea to have a mixture of weathering levels, so for example, I have mostly lightly weathered locos, with a handful of 'full works' weathered models, roughly 2/3rds lightly weathered, 1/3rd heavily weathered. There are no hard and fast rules with this and it really depends on the prototype being modelled - do what is most appropriate for your area.
The GWR 61xx (Airfix), Hymek (Heljan) and Class 45 (Replica) above have had light weathering applied.
The 61xx has had its wheels painted in Matt black and the front and rear pony truck wheels have been replaced with Gibsons as the originals did not have see-through spokes.
The Hymek has had its entire under chassis painted in a matt under frame dirt colour, which is a mixture of Humbrol 113 Matt Rust and Humbrol 33 Matt Black.
The class 45 has had a Craftsman detailing pack applied to the fronts of the bogies and the same under frame colour applied as the Hymek. This loco is an example of more 'modern' diesel traction where the weathering tends to take on an appearance very similar to coaches. Certainly, since steam has been abolished, general cleanliness on the railways has improved!
Due to the fact that they have no emissions, electric locos tend to stay quite clean although a very light dusting on the lower edges of the body as well as chassis treatment will improve realism.
The coupling rods of the steam locos have been painted using varying mixtures of Railmatch 'Greasy Steel', Humbrol 33 Matt Black and my standard track colour. Coupling rods are actually a difficult colour to reproduce because the prototype is actually steel covered in a greeny/browny grease.
The steam locos have all had their under chassis painted to varying degrees, some in Matt black, others in my standard brown.
The bodies of all three locos have had a light dusting of a brake dust colour brown (from 'Shades of Mud') applied using a goat-mop brush. It is important to do this lightly - you're only looking for a hint of brown tone, you're not after changing the loco colour to brown. The finish should be irregular and patchy - ideally a 'dusty' look. Dirt congregates in recesses and corners so these are good places to apply weathering. For this purpose, a stiff brush is good for working the powders into corners. Note that in the case of the diesels, the brown has been applied starting at the bottom and working upwards, higher in the middle with the 'plimsoll line' effect. Black has been applied to the roofs, working downwards.
It is important to note that weathering starts at the top and works down (weather) and also from the bottom and works up (track/brake dust). It does not start on the ends of the sides and go sideways and therefore, all brushing motions should go up and down. If you do it side to side, you'll get the weathering finish provided by some RTR manufacturers which looks like the train was running along and someone sprayed something at it when it went past - it'll end up with weathering which looks like it was applied at high speed. While this can happen on modern high speed trains, I haven't seen examples of it in any of my research for the 60's to late 80's period.
Weathering can be caught on the ends of vehicles, especially the leading end.
The 61xx has had black powder applied to the buffer beams to provide the characteristic effect of the period.
The 'Full Works' Weathering
The ex-GWR 43xx and 57xx in the picture above have had 'full works' weathering applied. This represents an advanced state of neglect towards the end of steam in the 1960's.
This type of weathering is considerably more time consuming to apply because more preparation is needed. The preparation takes the form of a complete paint over of the entire model using a base 'tone' colour, however, before this is applied, you have a good opportunity to file down any plastic moulding join marks such as those along the top of a boiler.
Both the 43xx and 57xx had a base colour or orangey/sand applied, very similar to that used on Stroudley's LBSCR 'lined green' (he was colour blind) livery as applied to 'Stepney'. The paint was applied as a normal coat like a top coat. It is not 'plastered' on as this tends to hide detail.
While the paint was still 'tacky' Carrs Powders (greys from 'shades of grey') were applied.
One popular misconception is that this type of weathering is brown in colour. In fact it is mostly grey with a hint of brown. Too much brown makes it appear like rust and this is not actually the finish we are aiming for.
In practice, I actually work on small areas of the model at a time. In this way, the undercoat base does not have too much time to dry - once it is dry it doesn't hold the powders as well. Having said that, different paints perform differently and some work better when dry, especially matt paints with a furry finish. You need to work out which way is best for your paint - remember if you start before the paint is dry and you end up wiping it off, then just start again.
Greys and a hint of brown were worked into both locos using an up and down motion.
When completed, both had coal loaded and representations of rust added at strategic locations:
The 43xx had some excess water applied on the back of the tender. This was a mixture of water, PVA and some white poster colour.
Once Carrs Powders have been applied some modellers 'fix' them using a spray varnish or artists' fixer. I personally don't do this because I find that fixers can take away the 'furry' textured finish provided by the Carrs powders. Weathering isn't just about colour. It is also about textures. If a fixer is not applied, you will find that if you touch a model, you may get some of the powders come off on your hands, depending on how well they were rubbed in.
I find that without fixer, the powders tend to absorb some atmospheric moisture which slightly changes the effect sometime after application. Normally, this results in the effects of the weathering becoming more realistic. Fixers will prevent this.