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"The Horror"
Tips and Techniques: Natural Metal Finishes
by Lee Rouse

 

OK, so that's not what Marlin Brando had in mind when he uttered those words in the movie Apocalypse Now. I think it's safe to say, however, that the idea of doing a natural metal finish conjures up all kinds of dark fears in many modelers.

So what's so hard about doing a natural metal finish (NMF)? Well, there are at least two issues that must be dealt with to achieve a good NMF. One is that the surface of the model must be extremely smooth, almost mirror-like. Unlike typical camouflage or drab military color schemes, any blemish or minor fault will show through, and actually seems magnified by the NMF. Secondly, there is the issue of "tricking" the eye into thinking that it's looking at real aluminum when it's actually looking at paint. This can be facilitated by using various shades of "aluminum", polishing out some panels more than others, etc.

There are many ways to approach the problem. My first natural metal finish was done about 10 years ago using the Floquil Railroad color "Old Silver" and polishing it out with toothpaste after it had thoroughly cured. Not exactly virtual aluminum, but it looked pretty good. I've also used SNJ, Alclad and Alcad II paints with success. These paints can be supplemented with SNJ aluminum powder which when buffed into the painted surface, will yield a brilliant and metal like finish. The Model Master buffable paints are useful for masking and highlighting specific panels, but too delicate for the overall finish (in my humble opinion, of course).

For my latest project, the Tamiya F-84G, I thought I would try something a little different, combining some tricks I have learned in the past with a couple of new ideas.

Preparing the surface. Fortunately, I started with an extremely well engineered model, the 1/48 Tamiya Thunderjet. The parts fit together beautifully. This meant that I did not have to do any major surgery or extensive puttying and sanding. The seams were joined with MEK (methyl ethyl ketone) applied through a Creations Unlimited liquid glue applicator. This little jewel is great for ensuring that you get the glue medium exactly where you want it. After the seams were dry, I used a White Out pen and ran it along the seams. The White Out pen is an improvement of the "old brush in a bottle" applicator that has been around for ages. Similar to a roller ballpoint pen, the White Out pen deposits a narrow line of White Out which can be precisely applied. Once the White Out is dry (I usually give it 5 minutes), the excess can be sanded gently away. I recommend starting with 600 or 1000 grit. I have even used 3200 grit effectively as a starter. In most cases, you will not need to use a grit coarser than 600. Remember, the courser the grit you start out with, the more scratches you'll have so sand and polish out.

This procedure will take care of most seams- remember, even the smallest imperfections will be glaringly obvious with a NMF. For those micro pits which persist, I apply a thin layer of super thin cyanoacrylate with a Microbrush. Put a small amount of super thin superglue in a bottle cap, dip the Microbrush in the glue, and run it quickly across the seam. After drying for a few minutes, the seam can be sanded and polished. This should take care of any pesky imperfections in the seam.

Polishing the Plastic. To polish out the plastic I use Micromesh polishing cloths. These come in a set and range from 3200 to 12000 grit ("grit" hardly seems the appropriate word to describe the higher number cloths, which have no perceptible grain). I try to start with the highest number possible in order to minimize the amount of polishing needed and avoid any sanding scratches. Do your work under a bright lamp. The kind that combines a lamp and magnifying glass is best as you can inspect your work as you go and detect any imperfections in the plastic. Large areas of the model surface may be shiny and smooth enough right out of the box to bypass this step. You don't need to achieve a mirror finish at this stage. The next step will take care of that.

Once you have sanded and rinsed the sanding dust off the model and let it dry, a coat of Future Floor wax can be applied. It can be airbrushed, but I've found that the finish seems smoother and glossier if I use a wide flat brush (" or 1") for application. Dip the brush into a small container of Future, rake off the excess, and apply a thin coat using one continuous stroke. For example, if I am applying Future to a wing, I might start at the wing root and drag the brush all the way to the wing tip without raising it off the model's surface. Immediately go back and load the brush with Future, rake off the excess, and apply another thin line parallel and slightly overlapping the first. If you need to go over an area again, do so immediately. Future sets up quickly and waiting more than 20 seconds to rebrush an area will result in visible brush marks. On the positive side, because Future sets up so fast, you can reapply a second coat to the model within 5 minutes. Usually two or three coats are all that will be needed to produce a mirror finish. Now set, the model aside for 24 to 48 hours.

Final polish. Once the Future has cured, inspect all surfaces under a bright light. Look for small imperfections. There will probably be some minute grains of dust imbedded in the Future. You can the polish these out. Start with 6000 grit polishing cloth, then 8000, then 12000. Wet each polishing cloth with a little water, and gently polish the surface with a circular motion. This will usually smooth out any small imperfection. If you need to, you can reapply Future over the area to restore the shine and ensure a smooth surface.

Time to Paint. Now for the moment you've been waiting for- applying the paint. Although I've used SNJ and Alclad, I decided to try something a little off the beaten path for this model- Krylon spray chrome paint. In order to airbrush the paint, it was obvious I was going to have to remove it from the can. First, I held the can upside down and kept the nozzle button depressed for several minutes until all the propellant was expended. Once this was done, a small nail was used to punch a hole in the can beneath the nozzle. (If you do this, BE CAREFUL, there may still be a small amount of pressure inside the can). Leave the nail imbedded in the can until the propellant is completely gone. This will allow the propellant to escape while minimizing any paint loss. Then you may remove the nail and pour the paint out into a container for storage. I know this procedure sounds a little scary, but it can be done safely if you take your time and use common sense.

The Krylon was very thin coming straight out of the can, but I found that I got better results if I thinned it even more before airbrushing. I tried lacquer thinner, which worked well. I then tried using a medium temperature automotive paint reducer (available at most auto parts stores), and than worked even better. I thinned the Krylon 50/50 with the reducer, then airbrushed at a very low pressure (between 10 and 15 psi) within 6" of the model's surface. I started with a mist coat, working with one section at a time (a wing, for example). After misting on a coat, you can go back over the same area with a slightly heavier coat. In fact, I found that a heavier coat was needed to produce the brilliant shine which looked almost like real chrome. One point of caution: only use this type of thinner if you have very good air circulation (e.g, a vented paint booth with an exhaust fan) AND wear a dual cartridge respirator (can be purchased at Lowes).

Shading the finish. Shading individual panels will break the "monochrome" appearance of the finish and give your model a more 3 dimensional look. Shading can be done in several ways. Rather than darkening the original chrome paint or apply another paint such as Testors Metalizer, I tried something different. First, select the panels you want to contrast with the overall finish. This is where reference material comes in handy. Individual panels must be masked off. This can be done with low tack drafting tape. For this job, however, I used Parafilm. The Parafilm was stretched, allowed to relax, and then applied over and well beyond the boundaries of the panel which is to be painted. Next, I CAREFULLY cut along panel lines with a NEW #11 blade and removed the Parafilm from the panels which were going to be painted. This left a very precise and cleanly masked border around the panel. I then thinned a Tamiya clear color (4 parts alcohol/1 part paint) and airbrushed it onto the panel, gradually building up the color with light mist coats. I used the Tamiya clear yellow to shade some areas, and the Smoke color for others. You can also mix the clear Blue and Smoke together for another tonal variation. Starting with heavily thinned paint allows you to build up the shading gradually. Because the colors are translucent, the underlying aluminum paint will appear darkened, not repainted.

Once the shading was complete, the Parafilm was removed, and a final thin coat of Future was handbrushed onto the model. I know that some modelers would consider applying a topcoat over the NMF as sacrilege, but I was pleased with the result. The Future is thin enough that it simply gives shine to the paint without really looking like a topcoat.

Once the Future had dried, I used artist's black watercolor heavily thinned with water and a drop of dish washing detergent to create a wash for panel lines. This was allowed to dry and the excess was then wiped off with a paper towel very slightly dampened with water. Decals were applied next.

So, that's it. My "method" of producing a NMF was really an experiment that fortunately worked out well. I'm certainly not advocating this as being THE way. I think it does illustrate though, that you don't have to do things strictly "by the book" to get good results.

Materials List:

Future acrylic floor wax
" to 1" flat brush
Micromesh (or other brand) polishing cloths
Krylon Chrome spray (or some better know modeling metalizer paints such as SNJ or Alclad II)
Medium Temperature Automotive Enamel Reducer (or lacquer thinner)
Dual cartridge respirator
Tamiya clear Smoke, Blue, Yellow
Isopropyl alcohol, or Tamiya thinner
An Airbrush (of course)