Foil Tips and Tricks
|Instead of finishing a
scale model with various types of "metalized" and silver paints
in an effort to achieve the much sought after "Natural Metal Finish"
(a.k.a. "NMF"), metal foil presents a unique and viable alternative.
The following article outlines some of the methods and techniques
I have come to find useful in recent months while researching
this elusive, sometimes-difficult, finish. As with many modeling
pursuits, there is probably much room to grow and expand upon
these methods and each modeler may find variations on the theme
to better suit their specific project or abilities. The basics
outlined below should suffice to get any intermediate or above
level modeler off to a good start on a foil-based NMF. As usual,
practice will greatly improve results and use of alternative tools
and methods may be required for the specific needs of a given
project. While foil does have some superior characteristics to
any form of paint medium in certain areas, it cannot be used in
extremely irregular and high relief applications. For these cases,
using a mixed-media approach is recommended to appropriately blend
the finishes of foil with paints. In my experiences, one of the
most resilient NMF finishes achieved by paint is from ALCLAD II
applied over an appropriate base coat primer.
TOOLS - THE BASIC STUFF
Let's begin by reviewing some of
the tools required to accomplish a metal foil finished NMF model.
Most of these tools are basic and easily obtained. A few others
are in the specialty category and may take a bit of research
to find in certain areas, although with today's Internet capabilities
this should not pose a major problem for most modelers. Scribers
come in various designs and each person seems to have a favorite.
I have found the different designs to come in handy at different
times depending on the application. I use both the "chisel tip"
and "pointed tip" commercial scribing tools in addition to a
homemade needle-in-a-dowel. Another indispensable scribing tool
is the back edge of the tip on my X-acto blades and scalpel
blades. The X-acto's are a bit more heavy duty and rigid while
the scalpels allow very fine and deep scraping of material.
In the end, I use eight different tools when scribing. Next
up are the pounce wheels. These may be tricky to find but are
really required. One problem with them is that each tooth on
the wheel is actually like a small slotted screwdriver when
examined closely. They will not properly make a round "rivet"
in the plastic and must be reworked. I used my Dremel tool to
carefully regrind each wheel to make the teeth into points vice
little wedges. Also, you may have to gently crimp the fork holding
the wheel to ensure it is tight enough to not wobble, but not
so tight as to prevent rolling freely. The wheel is apparently
high in iron content and will rust / corrode if not given a
light shot of anti-corrosion compound. For the various access
panels and hatches, not to mention connections and variations
of panel lines, a set of scribing templates is a must. I have
a set, which was purchased on the Internet from Verlinden, and
they have served me well.
The last tool, and probably the most
critical in foil application, is a set of burnishing sticks.
When applying the foil, it must be worked and burnished into
the surface gradually to allow it to actually bend, stretch,
and form along contours without tearing. This is done with wood
sticks as metal is too harsh. A small diameter acrylic or soft
plastic stick may work as well on heavier thickness foil like
that used on radio control aircraft, but I have been using wood
as it is a bit more gentle on the foil. The primary stick is
an ordinary round (not square or flat) toothpick. Sand one end
to a round tip and the other to a soft edged chisel (no sharp
corners or edges that will tear the foil). Another stick is
a ¼-inch square medium balsa stick, again shaped with a round
and chisel end. Occasionally I find use for one of my blending
stumps. These are the tightly rolled gray paper sticks with
a pointy tip used in blending charcoal, pencil, and pastel drawings.
Like the balsa stick they will become fuzzed up and worn with
use but are easily returned to shape with a coarse emery board.
Finally, a small piece from an old, soft cotton tee shirt for
buffing up patches of foil as desired. I have a bit of metal
polish on the rag, not much though, which helps remove any worked-in
surface scratches you don't want after the foil is down.
The basis of a correct and accurate
model is your documentation. Gather up the source material you
need and study it well. Use this information to plan ahead for
all the surface details you desire to apply. Where needed, you
may have to make sketches and diagrams to plan the scribing
and rivet job. A useful method is to lay the model parts directly
on a home scanner and make prints from them. These prints will
be exactly 1:1 and can be drawn upon with pencil to plan out
the panel lines and rivet details. To avoid clutter a scheme
can be developed, for example, whereby panel lines are thin
pencil, single rivet lines are dashed lines, double rivet lines
are dash-dot-dash lines, and if rivets are staggered a crossed
hatch on every other dash, et cetra. Be inventive and have fun
Because of the way the surface details
must be developed, an order of detailing is required. First
the surfaces must be marked correctly. Use an erasable soft
mechanical pencil rather than an indelible or water color marker,
which will clutter up the area. When all the panel lines are
marked and the underlying structure of the real machine is apparent,
mark location of all hatches and access panels and erase where
panel lines cross them. After all panel lines and hatches /
access panels are set into the surface, rivets will be applied.
It is important to have accurate panel definition so the rivet
orientations will be correct and places where rivets run along
underlying structure with no adjacent surface panel line will
be in the right spot. When planning rivet runs care must be
taken to allow for the spacing of multiple rows of rivets between
panel lines or along the edges of a panel line. Likewise, rows
of multiple rivets must be planned according to their spacing
as even "side-by-side" or staggered in a "zigzag" pattern.
Once the panels and rivets are defined
and applied additional surface work may be called for. Specifically,
the dents and dimples that often appear along riveted metal.
As the thin aluminum skin metal is riveted down it will sometimes
pucker and leave ripples and surface undulations, which add
a lot of character to the model. These surface anomalies are
applied last and will destroy some rivets however, replacing
the rivets is easy. Lastly, make sure all the panel lines and
rivet runs cross glue seams smoothly and accurately.
Before any foil job may begin, a
thorough preparation of the surface is mandatory. Once all the
surface details are identified and studied, the model parts
can be marked using a soft lead mechanical pencil to allow accuracy,
detail, and erasability for the goofs that will occur. Marking,
scribing, and riveting should be done to the maximum extent
possible on all parts before assembly due to the rough handling
they will receive. If the model has raised panel lines, they
must be sanded smooth first, or scribed along the raised lines
to establish the recessed panel line before sanding off the
raised part. Carefully mark all the panel lines per the documentation,
then mark all hatches and access panels that break a continuous
panel line. This will prevent you from scribing a line "through"
a panel or hatch. To scribe in the panel lines, use a piece
of DYMO brand label tape cut in half-lengthwise. This will lay
flat and steady on the part and act as a straightedge. In cases
of slightly curved panel lines, the DYMO tape may be cut more
narrow and "bent" as it is laid down or cut at a gentle curve
to match the desired contour. Don't try to over use the tape
as it will loose its stickiness and may slip as the scribing
tool runs along the edge. Stop panel lines short of hatches
and access panels and use scribing templates to make these.
Of critical importance is that you do not run the scribes lines
all the way to the edge of any parts where a glue seam will
be. It will be impossible to accurately scribe two parts and
have the lines "meet" at the seam. Leave some room and the lines
will be "connected" after the parts are glued together and the
seam is cleaned up.
After the panel lines and hatches
are established the rivet runs will be applied. For this I recommend
the pounce wheel to ensure linear rivet runs and consistent
spacing. In some tight spaces or awkward angles the pounce wheel
may not fit and the rivets will have to be applied manually.
For this I simply use my pin stick and work carefully for the
few that must be made. As in the case of panel lines, use DYMO
tape to mark the line where a run of rivets will lie. Place
the teeth of the pounce wheel into the edge of the tape at a
slightly inclined angle of 70 degrees or so to allow the teeth
to track along the edge of the tape and not "wander" away. Use
a gentle downward pressure and a somewhat "rocking" motion to
advance the pounce wheel forward and backward along the tapeline.
Making the sawing motion allows you to control a correct level
of pressure and achieve a uniform row of "rivets". The rivets
will in actuality be little "craters" or "volcanoes" on the
surface that appear as a hole. While you will see the hole,
you won't necessarily notice the raised "rim" of the crater.
Once the foil goes over this, the hole will be invisible and
the rim will define a microscopic rivet! Cool! Use care not
to overly handle and smash down these bumps for the remainder
of construction or you will be loosing your rivet detail.
One important note is that rivet
lines may not be a single row but may be double or more adjacent
rows. Also, the rivets in adjacent rows may be evenly aligned
side-by-side or staggered zigzag along the rivet run. To do
this you must mark one tooth of the pounce wheel with a permanent
marker and use this "index tooth" as the starting point on multi-row
runs. (Note: this indexing is also important for ALL rivet runs
so that you can run over the line again and not have the pounce
wheel create a "shadow" set of rivets next to the originals!)
This is required since the tooth spacing on a pounce wheel is
NOT even and varies slightly around the circumference of the
wheel. When beginning a run, start at the edge with the indexed
tooth. For the adjacent even row re-apply the tape in a parallel
line but moved over approximately half to one millimeter. Now
place the indexed tooth in the first hole of the existing rivet
line and gently move it sideways to touch the DYMO tape and
gently press it down to grab the surface. Then make the rivet
line with the rocking back and forth motion along the length
of the tapeline as far as needed. To make a staggered line,
find the first rivet with the indexed tooth and move it half
way to the second hole, then slide it over to touch the tape.
It is now aligned to that each tooth will be pressing into the
plastic half way between adjacent rivet holes. These technique
takes a little practice to master, but will provide consistent
and accurate rivet lines.
Many aircraft, which have riveted
skins also, suffer from a slight buckling and wrinkling of the
skin in the vicinity of some rivet lines. This subtle variation
is sometimes random, sometimes consistent, and must be evaluated
based upon your documentation. Since these variations are not
molded into the model you must apply them yourself in the appropriate
locations. To do so you must complete all the panel lines and
hatches, and establish as many of the rivet runs as possible.
Using a #15 scalpel blade scrape along the length of a rivet
line where needed to remove some plastic and make a bit of a
shallow trench on the surface. Next use 600 and 1500 grit sandpaper
wrapped on a stick, or carefully with your fingernail, to sand
across and along the trench to smooth the edges and make it
blend into the surrounding surface. Use care to work small areas
and not destroy too many nearby rivets. Keep in mind that ANY
scratches from the scalpel blade or sanding marks will show
through the foil and work to make the dent/dimple a smoothly
flowed "surface defect". After completing the dents and dimples,
you will need to go back and re-establish the rivets scraped
and sanded away. This is where having the indexed tooth is very
important! Start at the beginning of the run with the indexed
tooth or you will have a set of rivets which "walk over" the
original set. If in doubt of the correct spacing, gently roll
the pounce wheel over the rivets and see if the teeth cleanly
engage each hole or begin to run up onto the local surface and
get "out of sync". Again, a little practice on scrap stock will
go a long way in perfecting this technique. This can be next
to impossible on white plastic! Good quality medium gray seems
to be just about right for this step.
Depending on your model subject,
you may find a need for using multiple grades of foil. Not only
does it come in shades and sheens of aluminum, but in gold and
copper too. One of the neat subtleties of the foil is the way
in which the different grades take on different hues. While
all looking like "silver metal", the ultra-chrome has a blue
tone, the chrome a sandy tone, and the matte aluminum a white
tone. This variation will give you additional flexibility in
replicating natural metal finishes. The chrome and ultra-chrome
are very thin, soft, pliable and show all details very well.
The matte-aluminum is a bit less soft and feels somewhat stiffer.
When peeling from the backing, use care to not just pull it
away and have it roll up into itself! It's impossible to unstick
sometimes. Gently lift a corner or edge and while keeping slight
tension on the foil with your tweezers, pull up and away from
the backing so that the foil and the backing sheet form an angle
of approximately 10 to 20 degrees. Keep the foil as straight
as possible and bend the backing down and away from the foil
but stop just before the foil will separate from the backing.
Then grasp the foil and the backing where they still make contact
and gently pull the foil as you "roll" your finger tips to the
edge and let the backing paper separate until it only contacts
the foil over a few square millimeters. All this time the foil
has remained essentially flat and straight. Now, as the backing
is allowed to fall away, a tiny bit of curling may occur along
a millimeter or two of the edge, but the rest of the sheet is
straight and ready for use. This technique is also very useful
when pulling off a long thin strip of foil to avoid curling.
Plan ahead and use the grades and finishes desired while starting
from the lower aft part of the model and working your way up
and forward. Covering small separate pieces will help refine
your technique before tackling major assemblies. If you goof,
don't worry! Just peel it off right away and do it again. The
Bare Metal Foil will come off easily unless it has "set" for
too long. After it is "set", peeling it off is very difficult
as it will break up and you will find yourself picking at thousands
of stuck down foil chips on a sticky surface...not fun.
In general, the foil is soft and
will hug amazingly well on convex or concave surfaces. It appears
that if the foil won't hack the curve on the model, aluminum
sheet didn't hack the curve on the real plane either and there
will be a seam or panel line present to offer relief. I guess
things just have a way of working out. To apply a piece, carefully
set the foil over the area (trimmed so as not to waste too much
material!) and orient it. Beginning in the middle of the area,
start making a circular, swirling pattern with the rounded end
of the toothpick just enough to tack the foil down and flatten
out an area about 3 mm across. Check that the foil will make
it to all the edges desired. If not, gently peel up and re-orient
or get a new piece and start again. Now start working it down
by continuing to make circular swirling patterns while gently
pressing the foil into the surface. You will notice right away
how the foil is soft and begins to distort. Make the progress
slow and allow the foil to bend and adapt to the curves as you
go and work to advance the line of contact between the foil
and plastic. On very aggressive contours, you may have to make
a relief cut to allow the foil to warp into shape, just use
care not to cut too far into the part of the foil which will
remain on the model. Once laid down, you may want to use the
chisel end to run it up to a corner or work it into a panel
line. Trim it along the panel line with a gentle cut from the
tip of a NEW scalpel blade, or in a pinch use an X-acto blade.
Don't press too hard, and don't stretch blade use too far or
you may snag the foil and get a tear. Peel up the excess, then
buff the panel with the cloth. Sometimes a tiny wrinkle may
form as you go, just try to burnish a little harder and work
"along the contact line" carefully. Minor wrinkles may be eliminated
by aggressive burnishing using the round end of the toothpick.
This is okay, but on the matte-aluminum foil aggressive burnishing
will cause the foil to lose its rough surface and shine up,
looking like chrome foil...which may be desired in some cases
While foiling, be extra cautious
about keeping the area clean and free of dust. You don't want
a fan blowing or any other activity in the area. The most tiny,
almost microscopic speck of dust or hair under the foil will
show up with unbelievable clarity. Wiping the working area to
be covered and your hands periodically with a tack rag is a
Certain areas need care when applying
the foil. In particular sharp turns like trailing edges are
susceptible to being peeled up until they are fully "set". When
covering these, do the bottom first and burnish the foil up
from the lower surface and trim it so the edge of the foil is
90 percent around the curve to the top surface. A firm burnishing
from the edge towards the center of the upper surface with the
balsa stick will press the edge down well and not leave any
ridge to show through on the upper surface foil. Then, when
covering the upper surface, wrap it around 90 percent to the
bottom edge to ensure overlap and give it a firm balsa burninshing.
Use care throughout the remainder of construction not to rake
any tools or fingers across the trailing edges in such a way
that it will peel up the foil. After some set time and the clear
coat protection, there won't be any problems with peeling. On
very large surfaces covered in one piece, a small bubble may
appear where the foil was firmly attached earlier. Just re-burnish
with the balsa stick. This may happen in the same spot several
times, in which case you may want to gently pin prick the bubble
to let air escape and burnish down.
Covering a canopy frame is easily
done. Prepare the canopy by filing and sanding so it will fit
on the model like a glove, since you don't want to be doing
any more sanding or filling than required after it is attached.
Do the Future dip routine and let it cure for a few days. Along
the inner frames use the needle stick to press in the required
rivets using gentle pressure while "rolling" the stick in a
circular motion such that the end opposite the pin makes a small
circle with the pin pressing on the plastic. This will make
a small "crater" on the inside of the clear plastic canopy.
And yes, be careful on the edges because WHEN the needle slips
it does not slow down very much while it bores through your
fingertip (trust me on this one...). Cut thin strips of foil
the width of the frames and place them on the inside of the
canopy. Use wider strips to cover the inner edges where the
canopy will be glued and trim them to the edge. Keep all the
strips correctly oriented, gently burnish them down and avoid
scratching the interior of the canopy. Check the fit and trim
away the foil where contact is made with the fuselage. Now go
to the outside of the canopy and make a matching rivet on the
outer surface, opposite to each of the inner surface rivets.
Attach the canopy with a minimum amount of cement (a Touch-n-Flow
is great for this part) and clean up the joint. Do not cover
the outside of the canopy until you get to that part when covering
the fuselage. When complete, the canopy will look like tiny
plates of Plexiglas sandwiched into a riveted metal frame.
|WEATHERING AND PAINTING
Once all your foil is burnished down
and firmly attached its time to begin the weathering. While
some subjects may call for the clinically sterile, just rolled
out the factory door look, aircraft used in operational flying
seldom kept up appearances for long. Some examples were well
maintained, such as a Commanding Officers plane, but some normal
wear and tear is always present. Applying such weathering and
selective discoloring is a tricky task at best and can easily
be overdone. On a NMF job it takes a different approach to get
the "used machine" look. While painted surfaces can be worked
with many forms of dry brushing, pastels, washes, and off-toned
scale effect paint, the foil surface lends itself to a form
of "physical weathering" which paint cannot withstand. Look
closely at a vintage or WW II NMF subject and you will notice
thousands of micro-scratches and areas of dull metal where people
worked or walked. On some of the aircraft extremities the finish
is quite a bit nicer as not much activity occurred out there,
such as on the wing tips or the tip of the vertical fin. Thus
a primary method of weathering a foil job is to selectively
apply micro-scratches and dull the finish where appropriate.
Normal oil and exhaust staining and washes can be applies also,
but these should be left until the surface physical weathering
is complete and sealed.
So, how should we scratch the surface?
Do not use regular sandpaper! The foil is tissue thin and normal
sandpaper will instantly tear through it. A better method us
to use tiny square or oval pieces of 1500 grit paper about 3
mm by 5 mm. Glue the tiny patch of 1500 grit on the end of a
thin wood stick with a slightly rounded end, and use it where
needed. The technique I prefer is to gently twist and roll the
end of the stick around an area in a PLANNED fashion. This is
so you can put the micro-scratches in the proper area and make
them look random at the same time. Work slowly and hold the
stick at various angles as you use it. Periodically stop and
examine the area by rotating the model around so you will see
the multitude of scratches from many angles. The goal here is
to work the scratches in inconsistent directions so they emulate
the look of random scuffing.
Another weathering technique involves
making a specific panel, or an area, more dull than other local
metal, without exactly looking like the matte-aluminum. Again,
sandpaper won't serve this task well, not even the 1500 grit,
just too abrasive. The choice of material for this application
is a small trimmed square of green Scotch-Brite pad. The Scotch-Brite
offers enough abrasion to gently get into the surface without
tearing through. To use this type of dulling it is recommended
that the area to be worked be masked off with a very low tack
tape. Using the Scotch-Brite, and very gently pressure, make
circular swirling motions and gradually take the shine off the
foil and achieve a uniform dullness. In certain applications
it may be desirable to make the strokes in a consistent, unidirectional
pattern. This will give the look of brushed metal. Varying the
direction of strokes on adjacent panels will give them different
reflective characteristics in almost any lighting situation.
Again, let your documentation guide you and work slowly since
you can add a few strokes if needed, but unscratching the foil
is not too easy.
After panels have been dulled with
the Scotch-Brite pad the surface is very rough compared to plain
foil and will take pastels, washes, et cetra quite readily.
The good part here is that if you make a mistake, just swipe
it with a cloth and it all comes off. Using pastels or washes
can really impart some color to the finish and add depth, however
you must plan to make these additions one of the last weathering
steps and not handle the model too much. Since these are easy
to take off, and the fact that the foil itself is a rather soft
material susceptible to additional unwanted scratches, the surface
must be sealed and protected. My tests showed that properly
cleaned foil would take most paints very well. I chose to use
Tamiya X-22 clear acrylic since it is ultra clear and flows
on very smoothly with little chance of any yellowing like clear
enamel. I refer to X-22 as "ultra-pure-filtered-Future", because
that is how it seems to behave and it looks less cloudy. Once
you are happy with the finish and weathering, just shoot a light
coat of clear over the entire model (masked windows) and the
surface is "locked in".
There may be a need to paint over
the final finishes and this can be done safely is care is used.
Applying masking tape over any foil creates a risk of lifting
the foil with the tape. As stated earlier, the longer the foil
sets the stronger its bond, but the risk is still there. The
best approach is to use a very low tack type tape. The difficult
part involved here is that you will not be able to trim the
tape while it is on the surface or you will score into the foil.
If this happens you are almost guaranteed to pull off the foil.
Any masking to be done must be planned and the masks pre-cut
so they may be applied and removed without cutting on the model.
One technique is to use your decals as templates for complex
shapes and stripes. Scan the decal 1:1 onto regular paper. Lay
strips of wide Tamiya masking tape on wax paper with a slight
4-5 mm overlap. I like the Tamiya tape because it is fiber-like
and trims nicely, adheres and seals to the surface well, yet
has relatively non-aggressive adhesive. Using a glue-stick,
smoothly tack the scanned decal onto the tape and use a very
sharp blade to trim exactly around the color portion of the
decal. Now the tape under the decal can be removed from the
wax paper and gently laid in place on the model, but do not
rub it or burnish it. Next use the portions of tape "outside"
the decal to surround the decal on the model, laying them right
up to the edges and matching everything up. Carefully peel away
the "decal" part and leave the tape that surrounds the image.
Gently burnish the edges and shoot a light mist of clear acrylic
to seal the edge. Now you can paint away, but be ready to work
quickly when you put the airbrush down. While the paint is still
wet, VERY carefully, and VERY SLOWLY peel away the tape. Use
the technique whereby the tape is pulled away from the painted
area at a steep angle to prevent any lifting or paint hairs
getting on the surface. Make sure the tape is not pulled "up"
but rather is kept close to the surface, and pulled slowly to
avoid any stresses or lifting of the foil. An analogy is peeling
a paper label from a prescription bottle. If you peel or pull
too hard the label rips. Going agonizingly slow allows the glue
on the label to stretch and separate without damaging the paper
label. Here we do the same thing and allow the low-tack tape
to release and not put stress on the foil to plastic bond. Don't
forget to mist on a light coat of flat white or light gray primer
before shooting very light colors on the foil.
Now your model is ready to accept
decals, and the clear finish will help. Decals will go onto
unprepared foil, but having the clear coat sealed surface ensures
a uniform substrate upon which to work and protects the weathering
materials from decal solutions. Trim the decals close since
the small pieces outside the printed area are hard to hide on
this type of surface. Be sure to use quality decals that are
truly clear between letters and numbers since the Tamiya X-22
is crystal clear and any yellowed or off color decals will show
up as a weird color patch around your lettering. When finished,
give the entire model and decals another few thin coats of clear
acrylic and let it cure. Now the fully sealed surface is ready
for any washes you may want to apply. Using an oil based wash
is handy since the acrylic coating resists the solvents allowing
blending, gradual application, and correction of mistakes as
We are very fortunate to be model
builders in this day and age when so much new technology and
advanced materials are about. As kit manufacturers increase
the fidelity of their reproductions we have the opportunity
to build models to a level of quality not dreamed of before.
The fun part is sometimes getting to think outside the box and
develop our techniques and methods. Using metal foil as an adjunct
to finishing materials allows us to make surface replications
not feasible with paint alone. As modelers, developing the skills
to work in various mixed media allows us to have a deeper, more
complex bag of tricks to use in replicating the subjects of
our choice. The suggestions put forth to you above are only
a start, and will hopefully guide you to find more applications
and increase your level of enjoyment in future modeling projects.