Staining A Natural Metal Finish

My philosophy as a contributor to Airfix Model World magazine, has been from the outset, to create and illustrate methods that adhere as closely as possible to ‘Occam’s Razor’. In other words to seek and promote the simplest solutions to a modelling task. I’ll accept that my employment of that philosophical principle takes a few liberties with its strict meaning but it remains the case that ‘the simplest solution is usually the best’ is still the most generally understood translation.

And so it was with that area of paint finishing that sometimes causes considerable anguish – ‘NMF’ as it is commonly abbreviated or a ‘natural metal finish’. A well trodden favourite approach for varying such a thing is to pluck different shades from the shelf, mask off ‘selected panels’ and pretty much leave it at that. Perfectly fine to my mind – it adhere’s to ‘Occam’s Razor’ and is accessible to anyone with basic control of an airbrush or ‘hairy stick’ but there’s also scope for a properly variegated finish that imitates the kind of staining that lifts the NMF to an altogether more realistic level. And it’s simple.

You’ll need a model (Jedi master of the absolutely flippin’ obvious me). This was my choice, Tamiya’s 1/32 P-51D Mustang. Please ignore the ‘grey’ puttied wings (or see ‘My Tuskegee Hero’ for more information – AMW USAAF ‘special’ ) and focus on the fuselage in fresh Alclad II Aluminium ALC101. I did sojourn in the land of ‘mask and darken’ by doing just that for the panel under the exhausts, that photos often show as such.

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From there, the weathering road forked left and a tube of Michael Harding Lamp Black oil paint was deployed. Why ‘Michael Harding’ (MH) and not ‘that other brand everyone’s heard of’? Like ‘Occam’s Razor’, it’s again simple – MH has hand ground pigments that are extremely fine and outperform courser (and cheaper) mixes elsewhere. In this application, that propensity to mix with artist’s quality white spirit (mineral spirits in the US) results in creamy washes and is exactly what’s required.

A medium strength wash, comprising a pea sized drop of Lamp Black, married to three full eye dropper loads of that artist’s quality white spirit was made up. With the safety catch ‘off’, the model was held by the starboard wing, with the port fuselage side uppermost. A quarter inch round brush was dipped in the wash and fully loaded. 50% of that load was allowed to wick away by touching it to the side of the plastic mixing dish. From there, the brush tip was touched or lightly dabbed on the horizontal fuselage surfaces, some half  inch to an inch or so apart. There was no attempt to paint the wash on with strokes. Instead, small quantities were just touched to the surface and the wash was allowed to migrate outwards.

Applications would collide and mix, giving further variety of totally random staining. I guess six to a eight dabs were put on at a time and once spread, given a little accelerated drying with a hair dryer held far enough away so as not to blow the wash. No wash applications were made directly into panel lines. Some wash moved into panel lines and other detail but this was left to occur randomly. The model was sometimes tilted to adjust wash flow, as the port side was covered until the whole section was complete.

All that then remained was to flip the model so the starboard side was horizontal and the process could be repeated. Ditto the topsides and lowers, followed by a critical examination of wash distribution. Where it was deemed to heavy or insufficiently random a latex free gloved hand meant errant portions could be dabbed with a forefinger ‘pad’ that lifted a little paint (cleaned off on tissue before resuming) – the glove texture transferring to the model and adding to the effect. In tandem with this, marks could (and were) removed with an ordinary pencil eraser before tiny repeat washes back filled and completed what I was looking for. Last step on step one was to seal progress by drifting a light mist coat of Tamiya matt clear, cut with cellulose (lacquer thinner in the US) and to blow dry with the hair dryer. Here’s step one complete.

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Step two was a straight repeat of the above, again sealed as before.

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In the second pair of shots things may not have appeared to have changed much but the principal ‘gain’ is in panel line and detail definition. It’s in no sense ‘black’ but merely grey, exactly as was intended at the outset. The reward for this simple technique was the variegated staining I’d wanted and the resulting contrast with those grey wings was very much as exemplified by the Hendon Mustang.

On the flight line.

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Wish you well with it, if you give it a go. 🙂

Until next time.

Bad Wolf

Mixing paint

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Like cutting parts from sprues, mixing paint may seem as straightforward as breathing but it was Jon Bius, head honcho, monkey master and leader of Llamas at The Diary Of Abernathy who made me aware of the Badger electric paint stirrer. Before that point, it was the Tamiya paint paddle you see in the foreground for me, accompanied by furious wrist action like I’d never known, although my wife greeted this declaration with her doubtful face, followed by peels of shrieking laughter…

Although the instructions didn’t specify their use, I soon ditched expendable AA batteries for rechargeables and these are by far the best from all perspectives. A pack of four means ‘two in’ and two on standby. All told, it’s a simple bit of kit and no amount of manual stirring can get close to the Badger’s ability to ruthlessly blitz within seconds, your recalcitrant paint pigment back into solution. From  Tamiya and Gunze acrylics to Humbrol enamels, the resulting base paint is just plain creamy – no lumps, bumps or ‘paint asteroids’ to clog that .35 airbrush nozzle, just smooth, sexy paint as nature intended.

35mm plastic film canisters are my standard mixing receptacles and once again, the thinned paint is shown no mercy, as the Badger ensures the best possible airbrush ready paint. The clear(ish) liquid at the right hand back of shot is cellulose thinner in a battered bottle that’s been my cleaning station for the Badger, since acquisition. Having come out of the now mixed base paint and wiped off with some clean tissue, the Badger is dipped in the cellulose and triggered for a few seconds – enough to shed any remaining colour. A further wipe clean and it’s all set to go again. It takes longer to read about than actually do it.

But like The Force, there is a ‘Dark Side’ to this perfect paint pummeller. The only defence is constant vigilance. What follows will frighten horses and terrify small children, Viewer discretion is advised.

Picture the scene. Your current project sits comfortably on the bench, a secure distance from the ‘wet area’. Just one more colour to airbrush. You blitz the freshly thinned paint and reach for the cleaning station but this time your finger, that you’ve routinely left resting on the trigger slide for months, slips forwards in transit to the lacquer cleaner. From this point, time slows down. Like the moments before a car crash; you can see what’s coming but are powerless to alter the events or consequences.

All sounds in the modelling area and outside are blanked out. There is only the low, gravid hum of the motor as the shaft momentarily reaches maximum rpm in a fatal fraction of a second, accompanied by that familiar vibration through your hand. Then three things occur simultaneously. Your reactions catch up and pull back the trigger slide. Your conscious mind registers the unthinkable. Your eyes begin a terrible journey. It begins with the concentration of paint, that begins directly under the stirring disc and leads away, away across the modelling space and out of the ‘wet area’. The orientation of the paint fling is governed by an as yet, unpublished rule of the universe. The precise wording I’ve come to understand translates into something like this – ‘the layout and design of your modelling space is immaterial; wherever you position your model, it won’t affect the outcome, your puny human intentions are rendered impotent before the power of ‘The Farce’.

So, you look towards the model. The unerring accuracy is almost beautiful. You recall gun camera footage from a diving P-47, attacking a parked Ju52 and how the line of rounds march towards, up and over before continuing on a short distance. It mirrors what you see now – a perfect line of paint droplets leading towards, up and over before…

…continuing across the front lens element of your camera you left with the cap off behind the model. Regret is only compounded by there being no protective UV filter fitted…

So, regard your Badger as a ‘best friend’ but one commensurate with a live firearm with no ‘safety’, other than your trigger finger staying firmly off the firing button. Beyond that, it’s all gravy…

Nip and tuck…

Seasoned campaigners will already have their preferences in this regard locked ‘n loaded, so this is for anyone new (or relatively so) to kit mutilation, as well as the incorrigibly curious (like me) who just like to see how others do things.

My five friends, from the back and left to right.

  1. Sprue nippers. Capable of chopping through most sprue gates, their only real drawback is they may cause the plastic on the part to scar from time to time (ie – the act of closing the jaws tears a little plastic out of the part where it joins the gate), requiring a little filler to rectify. This is because they ‘cut and crush’ the gate (the part of the sprue frame that connects directly to the part itself), rather than ‘cut’ in the way a razor saw does for instance.
  2. No.10a scalpel blade in a retractable handle. There are innumerable ways parts can be ‘mapped’ on to a sprue frame. Sometimes access to a small part is so confined, the 10a is the preferred choice. You can either draw the blade over the gate repeatedly, until through or cut a ‘v’ in it that you deepen before repeating underneath on the side of the gate opposite. Never fit a blade to a round handle. One day it’ll assume a tiny life of it’s own, roll off the bench and with a high pitched ‘Wheeeee!’ dive bomb your foot, point first. It’ll hurt. The flat retractable holder stays put and the blade only needs to come out when it’s needed.
  3. Tweezer nippers. These are a step up in cutting power over the 10a and capable of accessing the same tight spaces. Again, they ‘cut and crush’ but to a significantly lower degree than full size sprue nippers.
  4. JLC razor saw. This gets the most use by far and has fine and ultra fine teeth. I use the latter on most applications, the principle being to cut only on the draw stroke to keep the cut accurate and controlled.
  5. Razor saw. A heavier version of the JLC, this is great for cutting gates ‘full width’, as you’ll see below in a subsequent image.

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Here’s a 1/72 engine for the Autocar in Airfix’s US Bomber Re-supply set. The part is small and the four gates are in locations where the moulded detail can be easily damaged if removal is attempted by cutting right next to the part. The crushing action of sprue nippers would be transferred to the part, pushing it away from them and distorting the other gates, likely causing tear damage. Best avoided.

Access for removal is tight. Time to travel a more circuitous route to where we need to get to.

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To avoid such damage, take a step back and a different approach. The heavier razor saw was used to cut the gates away from the sprue frame itself.

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The result is to now have the part completely released from the sprue frame, with the gate stubs far more readily accessible.

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Once the part is thus safeguarded, the JLC saw can be used with the ultra fine teeth to cut the gate stub free. Once again, cut on the draw stroke (as you pull the blade towards you). Don’t attempt to saw back and forth but cut on the draw, re-position the blade, cut on the draw again and repeat until the gate drops away. This helps ensure a straight cut. If you’re less confident about this, simply ease the saw slightly away from the part and then cut on the draw. The surplus gate left on the part can then be trimmed off with the 10a and tidied with 1500 grit abrasive paper.

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Here are the tweezer nippers in action. cutting at their tips causes almost no part distortion and they can access all manner of awkward gate placements but are obviously limited to smaller gates, as they exert less pressure than full size sprue nippers.

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The sprue nippers have a flat side to the blades. Orientate the flat side to the part for the cleanest cut. You can opt to cut a little further away from the part if you think the plastic may scar, then trim with the scalpel afterwards and tidy with a little 1500 grit abrasive paper as necessary.

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So, that’s the end of this mini-tour of one of modelling’s basic tasks. Think twice, cut once. Plan parts removal and as you’ve seen, don’t rush it. Better by far to make multiple separation cuts to free up access to the gates ‘off sprue’. Obviously the number of gate combinations and parts access you will potentially encounter in your modelling life is huge but the principles here will go a long way to ensuring parts damage is either eliminated or kept to a minimum. That means ‘frustration avoided’ and helps ensure a happy plastic basher. Beer and cider has the same effect too…

Have fun with that plastic!