How do you achieve a natural metal finish on a plastic model aircraft?

Throughout aviation history, many aircraft have been built and operated in an unpainted natural metal finish. During the Second World War, when large amounts of combat aircraft were produced manufacturers started to complete aircraft in natural metal finish. There were a number of reasons for this, the first is that if the painting stage could be avoided then more aircraft could be produced in a shorter time, thus speeding up production. Additionally many paint schemes, especially matt finishes can are not particularly smooth and so do not produce very aerodynamic surfaces. This in turn increases 'drag' which could reduce the speed of a plane and its endurance. In addition to this last fact, the paint finish on an aircraft adds a small but not insignificant additional weight.  Inevitably this will also have a small but noticeable effect on maximum speed and overall range.

Aircraft are traditionally built using an aluminium alloy called Alclad. Alclad consists of heat-treated aluminium, copper, manganese and magnesium. This considerably aids in corrosion resistance and offers good structural strength. Although due to natural processes it will eventually corrode, that process will inevitably take a significant amount of time. For military aircraft built in wartime, this was not a significant issue as due to attrition the life expectancy of any new aircraft was not expected to be high.

Although natural metal finish may simplify certain aspects for a modeller it also has some complications. Inevitably when painting a model in one colour there are certain advantages, i.e. fewer colours are needed and there is no requirement for time-consuming masking for complicated camouflage patterns. That said a natural metal finish presents other specific problems for the modeller. One of the most noticeable issues is that as the model is predominantly one colour there is less margin for hiding any imperfections encountered in the build process. A natural metal finish will tend to highlight any significant problems encountered during the assembly process. For this reason, it is beneficial to take extra time and care over any filling or sanding. When all structural tweaks are completed it helps to paint the model in a comprehensive coat of primer. This helps in the adhesion of later coats of paint and also helps ensure that the surfaces appear more uniform and as such helps to hide any imperfections from the build process.

Natural metal finishes can be very unforgiving if incorrectly applied. It can be difficult to apply these by brush as if incorrectly applied it can offer an uneven coat and show the brush strokes. It is better to apply these finishes with a spray can, or by airbrush. Both of these mediums offer a more even distribution and will also allow the paint to self-level, which will significantly aid in creating an even and unblemished finish. Applying a sealing coat at this time can also help protect the paint, especially if there is a further requirement for weathering or pin-washing to bring out panel lines and other surface details.