Skills Demo presented by Bob Bradford
Bob Bradford presented a demonstration of the technique he uses to apply aluminum foil to his models to replicate the unpainted natural metal aircraft finishes used by many air forces over time. He had two stunning examples in the form of a 1/72 scale MiG 19 (from the KoPro kit) and a 1/72 scale Saab J29 (from the Heller kit). These were finished in a combination of foil and metalized silver paints and presented a very effective illustration of just how effective foil can be. Bob’s detailed notes & diagrams were distributed to the club and are available HERE. However, it is worthwhile to summarize his explanation here as a general overview.
Bob begins with why he uses foil for natural metal finishes (NMF) such as used on USAAF aircraft at the end of WWII and most Soviet and USAF types during the ‘Cold War’. Simply put, he feels nothing looks quite like aluminum as the real thing! Of course, he cited other uses such as chromed metal on automotive subjects, commercial airliners and even figures where ‘metal’ effects are needed (such as polished armor.) He also indicated that metalizer-type paints are also useful in combination for complimentary effects but nothing provides the subtle “grain” and reflectance of foil. So, for him foil is superior even though, as he put it, “requires ten times the work!”
To create a natural metal finish using either foil or paint, both start out the same with as near-perfect a surface as possible. Since both methods use thin ‘overlaid films’ (on the order of .001” thick), foil is not any more forgiving of surface defects than the typical NMF “paint system”. However, foil requires more planning since much of the foil application is best done to sub-assemblies and not the completed model, due to the higher degree of handling required.
Planning accounts for much of the effort when foiling. To start, Bob pointed out that the layout of the panels must be organized and sectioned for efficient & effective foiling. He referred to minimizing seams but also balancing this with the appropriate number of sections over areas of compound curvature to combat wrinkling. Whenever possible, seams should fall on a panel line – and often do since aircraft especially are skinned subject to similar but larger considerations! From this analysis, a ‘section map’ is created using a suitably detailed 3-view plan (copies from the instructions are handy if detailed enough.)
Part of the analysis concerns panel coloration. This needs careful examination of reference images (both B&W and color) to see how reflectance & ‘hue’ of the individual panels are arrayed over the airframe. This is annotated on another copy of the 3-view to organize the various treatments, including use of metalizer paints as needed. ‘Grain’ orientation is also noted since this can be used on the model to help make the finish more realistic.
Once the panel & section maps are developed, then the application sequence must be decided. The general idea is to work one panel at a time, from ‘inside’ areas to outer, or from one side to another, always with the next panel being adjacent to the prior. In effect, each panel is defined by where & what it ‘looks like’ & when it is applied – all before cutting the first piece of foil.
Actual method of application involves first removing an easily handled piece from a roll of kitchen foil(!) Bob prefers kitchen foil since it tolerates ‘man-handling’ better, with “heavy duty” foil being even thicker than the usually quite sufficient ‘regular’ foil. Cost aside, Bare Metal brand self-adhesive foils are much thinner and not as suited for NMF because it tears more readily. Instead, Bob uses Microscale brand foil adhesive to secure the foil. He first cleans the foil as well as the model with 91% isopropyl alcohol and then applies the adhesive using a medium-sized soft, flat brush, working it carefully to prevent brush marks or unevenness, since such may show. Bob uses the etched side of the foil (aka ‘the dull side’) to apply the adhesive as it provides a better mechanical ‘tooth’. Once set per the bottle’s instructions, he can then cut a slightly over-sized section using scissors as needed.
Per the section plan, he then uses a low-tack masking tape to precisely ‘border’ the panel to be foiled. (Best to cut off the tape’s ‘factory edge’ first.) Then the foil is lightly placed in position, overlapping the tape & adjacent panel. Then cotton buds are used to burnish the foil, working from the center to the edges (but not onto the overlap), working carefully to avoid wrinkling the material. Once burnished, the excess is cut using a new #10 Xacto blade (new because any dullness will tend to ‘tear’ the foil), using a rocking motion to cut the overlap along the adjacent panel edge & masking tape ‘guide’. When the edges are trimmed and the tape removed, the seams are then finished off using further burnishing, a light sanding with a foam backed sanding stick and fine steel wool. The aluminum foil will actually accept some ‘stretching’ and blending due to it’s relative thickness (which Bare Metal will not, being it is ~ .0005” thick.) The foil adhesive takes quite a few days to fully set since it actually is evaporating from under the aluminum via the seams – obviously a slow process. In the meantime, a panel can be removed and redone if damaged. However, over time, removal becomes much more difficult.
Grain & coloration is then addressed, initially by ‘polishing’ the entire foiled assembly in the primary grain direction’ using steel wool. The individual panels can then be ‘grained’ according to the ‘grain map’. The foil itself has a natural grain, of course, that can be oriented as desired to induce contrasting or complimentary reflectance as needed. Alternative grain (say, on a diagonal) can be induced in the foil prior to application of the adhesive as well.
For coloration, Bob unusually takes advantage of clear and tinted overcoats to alter the appearance of the NMF. He noted that real aircraft generally are not as ‘shiny’ as the foil appears on the model. Hence, flat or satin clear coats can make the model more realistic by simulating oxidized aluminum & other wear. Clear tinted overcoats, while admittedly needing more experimentation on his part, was seen as a way to replicate heat “aged” panels and panels made of metals than aluminum. Bob’s philosophy is to achieve a finish that matches the ‘real world’ appearance rather than merely ‘shiny metal’ which tends to look toy-like & monochromatic, especially in smaller scales.
Bob’s full demonstration provided much more detail such this write-up only provides a quick overview. His full notes provides examples of Bob’s planning maps (which are of course reusable), material lists and additional details (such as using toothpicks to emboss rivet and panel line details). He showed that achieving an effective natural metal finish isn’t magic but rather, when tackled in a methodical and logical fashion, can – without a doubt – provide ‘astounding’ results.
[Some other articles on NMF techniques can be found on the web at the following sites (as of 27 Oct 2014):]
- Twin Cities Aerohistorians – paint
- HyperScale (Part 1 & Part 2) – paint
- IPMS Houston (PDF) – paint
- FineScale Modeler (PDF) – foil