- A Simple Technique to Engrave Details on Brass Sheets
by Rogerio "Rato" Marczak
This 1/32 P-40 pilot's seat was scratchbuilt using the embossing
WRONG WITH PHOTOETCHED PARTS?
Everyone knows very
well the problems associated with many detail parts that come
with injected 1/32 kits. They may be way inaccurate - in shape
and dimensions. Even in the most recent releases, when the outline
of the parts is generally correct, a simple check with a caliper
will show that the thickness of many parts is out of scale.
In this article we explore a good example: WWII aircraft seats.
In most cases those seats were manufactured with steel sheets.
To save weight, the sheets were 2 or 3 mm thick at most, so
the stiffness of the part used to be increased by stamping several
"ribs". In 1/32 scale, 3 mm means approximately 0.1 mm, a thickness
impossible to be achieved with mass production injection process,
at least for a part of that complexity. Let alone include those
ribs and other smaller details.
You may be thinking:
"No problem... I'll order that photoetched part just released".
I agree that PE details are really handy in many cases. But
in some other cases PE parts are simply too "flat", they lack
some three-dimensionality. In addition, you can't always find
the PE set you need. Even if you do, there's another problem
largely ignored: How many of us check the accuracy of the PE
parts before using them? Not many, I guess. This is understandable
since the PE manufacturer is supposed to be in charge of the
research work, and it should be that way because the stuff is
not cheap. My point is: a given PE set is designed to be used
with a particular model, and it means that some "adjustments"
are necessary to make everything fit well in the kit. Even worse,
many details are faked as raised areas on the brass fret. Although
this is perfectly acceptable for 1/48 and smaller scales, in
1/32 these flaws become more visible. The seat ribs I mentioned
above is a good example: in a PE part they would look as stripes
- not rounded indentations.
Fortunately we are 1/32ers,
and so it is possible to scratchbuild many things that wouldn't
in other scales. In this article I'll describe a very simple
method to engrave details on brass sheets. We will apply the
approach step by step in a P-40E seat, but the technique has
many applications. I learned about the principles of the method
some years ago, watching an artist burnishing details in very
thin metal leaves for an ornament. Some months ago I bought
some 0.1 mm brass sheets to learn photoetching and found an
excuse to give it a try. It was not working for flat detail
parts because each time you emboss a thin sheet it will bend
heavily (as well as when you cut it with scissors). To recover
its flatness, all you need to do is to apply the well known
tip to straighten PE parts: roll a cylinder over the sheet,
flip the sheet and do it again.
If you can live with
the kit parts, stop reading now.
A BIT OF REVERSE
The first thing you
need is a good line drawing of the developed seat. You can do
it by hand, but with a CAD system it will be easier to make
the necessary modifications. In addition, it saves a lot of
work in future projects that use similar parts. If you are fortunate
to have access to engineering drawings of the subject this is
an easy task. If you don't, you will need to exercise some reverse
engineering to obtain a drawing with reasonably correct dimensions.
When in doubt, use your artistic license. Sometimes the dimensions
of the kit part are correct, so you can use it as a starting
point. When done, print, cut and assemble the seat as a paper
model. Check carefully for possible mistakes or misalignments.
Correct the drawing and repeat if necessary. Once you are satisfied
with the shape, add all visible details to the drawing: reinforcement
ribs, rivet lines, depressions, attachment points etc. Make
a few copies of the drawing and set aside.
Preparing the line drawing. In the detail, the
"paper model" of the seat, used for checking purposes
Well, it is not any
AC/DC... but heavier than plastic. Get some brass sheets of
the correct thickness (0.1 mm, in our case). Note that you will
find two major types of thin brass sheets: the hard one and
the soft one. Use the soft one if possible, because the hard
type is severely annealed and won't enable scribing so well
as the soft. You can also normalize the hard brass by holding
the sheet over a flame for a half minute or so and letting it
cool at room temperature.
This is all you need to start
a rectangle slightly larger than the seat drawing out of the brass
sheet. I use ordinary scissors, as the sheet is very thin. You
will notice that the sheet will bend heavily around the cut line.
To solve this, find a 20 or 30 mm diameter steel cylinder. Be
sure the cylinder is free of scratches or imperfections or they
will be transferred to the sheet. Now roll the cylinder over the
sheet, pressing it as it roll using your finger. Increase the
pressure around the bent edges of the sheet. The sheet will buckle
slightly. Flip the sheet and repeat the process. This should leave
a very flat sheet.
The brass sheet after cut
Roll, baby, roll...
Magic: the sheet is free of bents
TO STAY AWAY FROM STYRENE FOR HALF AN HOUR
Next you have to glue
the seat drawing on the brass sheet. You can use diluted white
glue, but I recommend a liquid contact glue. I use Microscale
Foil Adhesive hand brushed. Let the glue dry and lay the drawing
on it. Roll the cylinder to avoid air bubbles. Now trim the
excess of brass around the seat to facilitate handling and the
final trimming. The sheet will probably buckle again... roll
the cylinder every time this occur.
The adhesive foil applied over the brass sheet
Gluing the drawing
Trim roughly the excess of brass around the drawing
it would be very difficult to run any tool over the paper side
(it wouldn't slip well), we use a simple trick. Using a compass
needle or your favorite needle, mark a small point at the beginning
and at the end of each rib line. This will leave a small "rivet"
on the line ends. Double check to not forget any line because
the paper will be removed soon. Next, use a small scissors to
trim the brass. Try to follow the contour of the drawing the best
as you can. Now the seat is virtually done, just like a photoetched
item. Finally remove the paper from the brass sheet. Another hint
here: brush a coat of lighter fluid on the paper. Wait a few seconds
until the paper absorb the fluid and the paper can be peeled away
easily. Time to add the details...
These "rivets" mark the beginning and the end of each rib
All the excess of brass is already trimmed
EMBOSSING THE DETAILS
The embossing technique
actually starts now. Basically, embossing means to engrave the
details onto the surface. Contrary to scribing, there's no removal
of material. Instead, the material is pushed down in such a
way that its "negative" appears on the back side (the reason
why it can be done only with thin materials). Every time you
emboss a detail, it causes high localized deformations on the
area which make the sheet bend. The secret to straighten the
sheet is to use the cylinder when you fell that the sheet has
bent too much, and then resume embossing. More importantly,
the cylinder compression reduces all the engravings to the same
height, so you don't need to be perfectly consistent with all
the details as they will be leveled down. It can't be done with
plastics because most plastics can't be flattened once embossed.
Well, you will need
at least a couple of "embosser" tools. I heard that there are
craft tools specially designed to emboss metal plates, but you
don't need them. Almost everything can be used as tools here,
depending on what you are going to do. If you have to slide
the tool (like the ribs of our seat), better to have a tool
with rounded tip. For engraving ribs, I use some burnishing
tools, those used to apply dry transfers. They have small spherical
heads in three sizes: 0.5, 1.5 and 3.0 mm. However, one of my
favorites is an empty "roller-ball" pen. I use an old compass
needle mounted in a handle to make rivets. For smaller details,
those mini-screwdriver sets provide valuable tools, too. You
can make every sort of tools using many things you find at home.
And of course you also need a ruler.
Some examples of tools I use for embossing
To make the ribs on
our seat, just join the points marked earlier with a rounded
tip tool. Using a ruler as a guide, make a light pass first,
then increase the pressure and repeat two or three times more.
In a 0.1 mm sheet, this should be enough to make a deep engraving.
As I said before, you don't have to be perfect with all ribs
as they will be leveled down by the cylinder. Believe me, it's
easy. I scribed the entire seat in less than 10 minutes.
Embossing the ribs (I'm not left hand, and sure I should be
holding the ruler with my other hand. But how the hell I would
hold the camera?)
This is what you get after mere 10 min of work
A close look at our job
Not much to talk about
here, if you have previous experience folding PE parts. I use
a flat lip pliers and fold the part along the pliers edge using
a small block of aluminum. Use moderate pressure to avoid damage
to the embossed details in the clamped area. Always fold a bit
more than necessary to account for some spring back (I mean,
if you want 90 degrees, fold about 5 degrees more as the fold
line will always return a bit). If you prefer, score the folding
lines with a hobby knife first - it will make things easier.
The picture below shows the result. Note that the seat back
plate is wider on top. This is because it will be rounded later,
so that the side walls will become parallel (take it into account
during the drawing phase).
Folding the seat
Now it looks like a seat, huh?
I FORGOT THE RIVETS...
Well, this step should
go along with the ribs. I forgot to add the rivets lines. I
had to unfold the seat to add them. No problem in doing it once,
but if you fold/unfold repeatedly it may crack along the fold
To add the rivets I
use those saws that come with office tape holders. Their tooth
are already very sharp and you can sharpen them even more with
a file if necessary. The basic procedure is simply to press
the saw along the rivet line. Try to distribute the pressure
equally on the tooth. Once done, they will seem a bit exaggerated.
Roll the cylinder again... and they will be just fine - very
subtle. Then I folded the seat again and added the curvature
of the back plate using the same cylinder on the inner side
and my finger on the back side. Start making a very gentle curvature.
Slowly roll the cylinder against your finger with the seat between.
Keep on until the side walls of the seat are parallel. The joint
lines were glued with Future Floor Wax: hold the joint in position
and brush a good amount of Future. Let it dry and then remove
the excess with a cotton dab moistened with denatured alcohol.
The picture below compares the seat before and after adding
the round back and the rivets. Note the color differences. That's
This is my "riveter"
Before and after adding the missing details
Now it looks like a seat, huh?
Finally, we add a few
more details manufactured with the same technique. The reinforcement
plates onto which the seat struts are attached were made with
aluminum foil. Just cut small rectangles of proper size and
punch the rivets inside each corner. Once again, roll the cylinder
to level down the raised marks. Be very gentle in this case
because the aluminum is much softer than the brass. If you exaggerate,
the rivets will simply disappear. Fix them with your favorite
slow setting glue.
The back reinforcement plates already cut and ready to install
Gluing the attachment plates
How it looks after installed
Today this is one of
the most used techniques of my personal repertoire. If it sounds
intimidating, let me tell you: try it! It is really easy and
I bet you will get good results on your first trial. Believe
you or not, the seat used in this article was obtained in my
second attempt (the first one worked, too).
A test fit in the Scratchbuilders 1/32 P-40B conversion fuselage.
In the detail, my chief test pilot for this project, "Jimmy
Curtiss", in a test flight with the new seat
The method has many
other uses, but I found it particularly useful to make bolted/riveted
plates. I even made a cockpit switch box embossing buttons and
switches of several sizes. Let your creativity flow and I'm
sure you will find many applications or variations of the technique.
Give it a try.
My scratchbuild 1/32 P-40B
right sidewall showing some details added with the embossing