it yourself photoetching
...or how to wreck your home with
Author's Note: This article was written some
time ago, when I had ready access to the chemicals mentioned in this article. At present,
I have not done photoetching in-house for some time, and the company that produced these
chemicals is no longer marketing them. Therefore, I have no clue where you can get these
chemicals at the present time.
There comes a time when every model builder faces the
dilemma of a part that is too small or detailed to be scratchbuilt, yet cannot be left out
for the sake of convenience. Photo-etching has quickly become the method of choice for
duplicating small detail parts that could not other wise be done. Excellent examples of
photoetch parts include screens and grilles, landing gear and access doors on aircraft,
seatbelts and harnesses, ship railings, and even automobile parts. This article describes
a method for producing photo-etched parts from standard hobby store .005 inch (0.13 mm)
thick sheet brass.
There are several methods of developing parts, the most common
is the duplication of an original. One important aspect to remember is that single side
etching will not produce relief details. The results are flat pieces of brass that have
features that cannot be achieved by mechanical means, or by laser cutting. (If anyone has
a lasercutter in his basement, please let me know...) You will need to create a drawing of
the parts you plan to produce in pencil on drafting paper, typically 50% or so larger than
the actual size of the part. The reason for creating the pattern larger is this: when the
pattern is reduced, the detail is carried over and the spaces in the brass become very
small. Draw the pattern in a manner that will allow runners, or connection points that
hold the parts to the frame, like a sprue of plastic parts, with an outside frame of metal
surrounding the desired parts. The runners keep small parts from falling into the bottom
of the etchant pan. When designing the sheet of parts, you should also try to minimize the
amount of brass that must be removed from the sheet . This is important as the etching
solution will work faster and last longer if there is less brass to etch. Once you have
the design for the entire photo-etch sheet mapped out, you should transfer the pattern to
frosted mylar drafting paper (available at art/drafting stores) using a #0 black technical
pen. Color in the parts (corresponding to the brass not to be etched) using a #2 technical
pen. Take the mylar artwork to a shop that can make a "film-positive" from the
mylar original. Most shops that make blueprints and reproductions of architectural
drawings can do this . When you have the positive made, you should specify the amount of
reduction you need so that the positive is the actual size you want the etched parts to
be. The article suggests you draw a "scale" on your original that should map to
1 of your favorite units of length when the reduction is done - e.g. if you're working at
5x actual size, draw a 5 inch (or cm) line along one edge of your artwork. You can then
double check the reduction by measuring the line on the film positive - it should be 1
inch (or cm).
Something to consider when producing really small parts: If youre
seeking super-fine detail, consider using stainless steel instead of brass. The etching
will take longer, but the results are impressive, and the steel etches more sharply than
Several people I have talked to have used CAD (Computer Aided
Drafting) packages to print directly to a laser or inkjet printer. If youre not a
computer type, then skip this paragraph. If you are then youll need to adjust your
printer to handle the highest resolution it can handle. The higher the resolution, the
better the curves, and the finer the overall detail. Create the drawing, and do your
editing on the pixel level with photo-retouching software (Photo-styer, PaintShop, Lview
Pro 1.6B). Transfer the drawing to a transparency, then continue on to the next step.
The next step is to transfer the artwork from the film positive
onto the brass. The first step is to thoroughly clean the brass sheet as if you were going
to paint it - wash with detergent, rinse and air dry. Spray both sides with a few coats of
photoresist and allow to dry for a minimum of 60 minutes. The drying process can be
assisted with a hairdryer. If you have the luxury, let the raw brass set for 24 hours.
Keep the brass away from bright light until you are ready to expose it.
Next step is to expose the photoresist. You want sandwich the
brass and the photo-positive between a piece of glass and corresponding surface such as a
piece of finished lumber. Hardware stores have pre-made shelving boards, they come in
various sizes and are pre-finished. Place the resist coated brass on the lumber, the the
film positive on top of the brass, then cover the whole thing with a sheet of glass. Use
real glass, as Plexi tends to be too flexible and too light. It is very important to make
sure there is no air space between the brass sheet and the photo positive. Any airspace
will result in a ragged etch. Clamp the whole sandwich together. Youll need a UV
source to expose the photoresist, and the best part of this step is that its free.
Place the brass outdoors in bright sunlight for 3-5 minutes, 5-8 for cloudy conditions.
You may to experiment with exposure times, as factors such as temperature and angle of the
sun will vary the effects and exposure times. NOTE: This
procedure doesnt work at night. After youve
exposed the brass, you should remove the plate from any light source until it can be
developed. I recommend developing the brass immediately after exposing. SHORTCUT: If you
simply want to duplicate an already existing photoetch part or tree, simply substitute the
part for the photo positive.
Next, you develop the brass - i.e. remove the exposed parts of
the photoresist. Developing is done with a lye (sodium hydroxide) solution - better
electronics shops will carry this. Put the exposed plate in a plastic or glass tray, and
cover it with the developing solution for a few minutes. Rock the container to agitate the
solution. Remove the plate (wear rubber gloves and use forceps or needlenose pliers) and
check the development process - the pattern should appear on the brass, and then
disappear. This occurs within 5-7 minutes of soaking. When the pattern disappears, the job
is finished. Rinse under tap water to halt the development process. If you overdevelop the
plate, the etched image will be fuzzy and unusable. Put the plate back in the developer
solution until all of the resist is gone, and start over.
The etching solution is ferric chloride. Ferric Chloride, or
etching solution, is a red brown liquid available at Radio Shack or from GC Electronics. A
32 oz. Bottle should run about $5.00. You need a plastic or glass container that will hold
the sheet of brass - a glass cake pan works well. Pour in the ferric chloride solution
about 1/2 deep, and place the brass sheet in face down (so that the etched brass falls
away from the surface of the sheet). It is necessary to keep the etching solution
agitated, new fluid needs to be circulated over the surface of the brass. A simple method
is to use an air source to create a whirlpool effect. TRICK: I use my airbrush air hose,
clamped to the side of the pan at an angle, to keep the fluid circulating. Remove the
plate and check the progress every 15 minutes or so, until the brass is fully etched.
Typical etch times are given as 1.5 hours with new etchant, longer with used. Rinse with
lots of water to stop the etching process. Ferric chloride is then disposed of by flushing
down the toilet. Authors Note:I questioned the disposal of the used ferric chloride,
but the directions on the bottle clearly state that it can be flushed.