Date: Mon Aug 3, 1998
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** How to make your own photo-etched parts.
This is a single question with several long answer.
[Q] How do I make my own photoetch parts?
If you have web access, check out the following related urls:
[A] firstname.lastname@example.org (Don Schmitz)
Here is the summary of the "do-it-yourself" photoetching article that
appeared in the Sept. 1993 issue of "Fine Scale Modeler". This is a
nicely done article, written by Rusty White , who runs a small
business producing photo-etched ship details. I've tried to extract
the useful information in the article so as to minimize both my typing
and the chance that I would violate someone's copyright.
I want to point out that I haven't used this technique myself - I just
happened to pull this magazine out to consider giving it a whirl for
a project I'm starting, when the request for info showed up here. I've
double checked all of the details, but please let us all know if you detect
something that looks wrong.
Finally, I've added editorial comments based on information bouncing
around my head that I can't attribute sources to - other articles,
former r.m.s postings, and a few of my own thoughts. Some of these are
speculation on my part, and I want to make sure that they are
recognized as such, and not taken with the same authority as the
information contained in the FSM article. I've identified these comments
with square brackets (s) in running text, and >>> where I ramble on
The article outlines the procedure for producing photo-etched parts
from standard hobby store .005 inch (0.13 mm) thick sheet brass. The
article states emphatically that the etchant described (ferric chloride)
will destroy aluminum sheet, and seems to imply that it will have no
effect on stainless steel.
>>> This process should also work with similar sized nickel-silver
>>> sheet if you can find it. You can probably push the thickness of
>>> the sheet up to .02 inches (0.5 mm), but you will tend to get
>>> less crisp edges - as usual, some experimenting is in order.
1. Designing the parts.
The articles suggests that you first draw a draft of the parts you plan
to produce in pencil on drafting paper, working in a reasonably large
scale - typically 3 to 5 times actual size. You should design the pattern
much like a sprue of plastic parts, with an outside frame of metal
supporting the desired parts via small "runners". The runners are
needed to keep small parts from falling into the depths of the etchant tank
[unless have a source for the adhesive-rubber backed brass sheets that
are used for many commercial photoetched parts].
When designing the sheet of parts, you should also try to minimize the
amount of brass that must be removed from the sheet (in order to
extend the etchant life and minimize etching time). This implies
filling in large open areas with "dummy" parts, or drilling holes in
the open areas.
>>> Speaking as a one-time mechanical designer/draftsman, you have to be
>>> careful when working at 5x actual size to not design parts that are
>>> ridiculously small in actual size. For example, say you plan to
>>> produce a car grill, and draw perfectly reasonable looking 1/16-inch
>>> wide grill slats at 5x actual size - corresponding (assuming
>>> a 1/24th scale model) to a .3 inch thick slat on the 1:1 original.
>>> This corresponds to a .01 inch (.25 mm) wide feature on the 1:1
>>> photo-etch sheet - about the width of a thin pencil line. My guess
>>> is that such a feature will simply disappear when etched.
>>> The article doesn't mention it, but I expect that the resulting
>>> etched parts will be slightly smaller than the artwork, by about the
>>> thickness of the brass sheet being etched. If this source of error
>>> matters, you will have to experiment to find out how much width you
>>> lose to etching and exaggerate small features to compensate.
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.
You then take the mylar artwork to a shop that can make a
"film-positive" from the mylar original. Supposedly most shops that
make blueprints and reproductions of architectural drawings can do
this [another article claimed a cost of roughly $7.00 US for one such
reproduction]. 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 - eg. 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).
>>> A frequently asked question is whether you can prepare the artwork
>>> yourself, using a reducing photocopier to get the size right, and
>>> then photocopying onto a transparency to produce a "film positive".
>>> Or, alternatively, using a CAD package to generate the original
>>> and printing directly on a transparency. At least one poster to
>>> r.m.s has reported success with this basic approach. A few possible
>>> - many photocopiers and printers introduce (slight) distortion in
>>> their output ie. straight lines on the original are slightly curved
>>> on the copy. This is probably not significant for small parts that
>>> don't have tight fit requirements. The distortion tends to be
>>> worse near the edges of the page, so you may be able to work around
>>> this by centering your artwork in the middle of the page.
>>> - most photocopiers and laser printers have a hard time producing
>>> large black areas, especially on transparency plastic - the centers
>>> tend fade to white and there are often small white marks scattered
>>> about. You may have to do some touch up with black paint.
2. Transferring the design to brass
The next step is to turn the artwork on the film positive into a resist
pattern on 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 24 hours. The source listed in the article was from a company in
the UK, it is:
Electrolube RP50 Positive Photoresist
PO Box 3
Essex SS6 8LR
Approx. cost $25 for a large spray can, including shipping and
international money order.
An alternative, US source was given as:
1801 Morgan St.
Rockford, IL 61102 (free catalog)
Note: This photoresist does not change colors when exposed and developed
as described in the following text.
Next you expose the photoresist. Take a sheet of 1/4 inch plywood or
similar stiff material, add a thin layer of foam rubber, follow with
the resist coated brass, then the film positive, top with a sheet of
glass, and rubber band the whole thing together. You need a UV source
to expose the photoresist, the FSM article suggests direct noon day
sun for 2 minutes, add another 2 minutes for cloudy days. Other articles
suggest plant grow lamps or sun lamps. Once exposed, you should remove
the plate from any light source until it can be developed. With the RP50
photoresist, a correct exposure results in a yellow tint.
Next, you develop the brass - ie. remove the exposed parts of the
photoresist. Developing is done with a lye (sodium hydroxide) solution -
a chemical supply house is suggested as a source for the lye. Create a
"stock" solution using 20 grams of lye to 250 milliliters of water, and
store this in a bottle clearly marked "poison". For the actual developing
work, dilute 1 part of the "stock" solution with 7 parts water.
Put the exposed plate in a plastic or stainless tray, and cover it
with the developing solution for a few minutes. Rock the container to
agitate the solution. Remove the plate (wear gloves and use tongs/tweezers)
and check the development process - the previously exposed areas of the
resist should wash away, leaving the brass that is to be etched away
exposed. If you use the RP50 the remaining photoresist should turn
a green color. When all of the exposed resist is gone, rinse under
tap water to halt the development process.
If there are minor flaws in the resist image, you can touch it up with
a technical pen - the ink is an effective resist. If you overdevelop
the plate, the photoresist image will be fuzzy and unusable. Put the
plate back in the developer solution until all of the resist is gone,
and start over.
3. Etching the brass.
The etching solution is ferric chloride. The article suggests you buy
dry ferric chloride from a chemical supply store, and create a solution
of 250 grams of ferric chloride to 600 milliliters of water. The article
warns that ferric chloride will stain just about everything, and is a
nasty corrosive chemical - so wear gloves and treat the stuff with respect.
[I think Radio Shack sells ready mixed ferric chloride solution in 32 oz
bottles for about $3, probably much more convenient to buy and use].
You need a plastic container that will hold the sheet of brass at a
roughly 45 degree angle - a margarine tub is suggested. Place the
brass sheet in face down (so that the etched brass falls away from the
surface of the sheet), and pour in the ferric chloride solution. It
will bubble and fume, so this isn't something to do on the kitchen
table. Remove the plate and check the progress every 15 minutes or so,
until the brass is fully etched. Typical etch times are given as 3
hours with new etchant, longer with used. Rinse with lots of water to
stop the etching process. The etchant can be saved and reused, but it
will gradually lose its effectiveness as more brass is dissolved in it.
Again, you should label the etchant as poison and treat it as such.
>>> The Auto-Etch photo-etch system you may have seen advertized in
>>> recent model magazines uses the same etchant, and includes a heater
>>> and circulating pump for the etchant to speed up the etching process.
>>> If you're reasonably handy, you can probably duplicate these features
>>> with a fish-tank heater or hot-water bath for the etchant tank, and a
>>> fish-tank air pump bubbling the etchant to keep it circulating.
4. Finishing up.
You now remove the photoresist from the parts by placing the brass sheet
in some of the "stock" (full strength) lye solution. Rinse with lots
of water, and your photo-etched parts are done!
>>> Something to think about: unless you need to produce many identical
>>> parts, you could skip the entire photo transfer process and draw/paint
>>> the parts with a suitable resist right on the brass, perhaps using
>>> a stencil or masking tape to get clean lines. I think lacquer paint
>>> is a fairly good resist, and is readily available in spray cans.
>>> The paint/resist can then be removed from the finished parts with
>>> your favorite stripper - eg. oven cleaner or brake fluid.
[A] RANDY.GORDON-GILMORE@ocr.com (Randy Gordon-Gilmore)
Date: Fri, 15 Jul 1994 10:21:41 GMT
I have been doing my etching for about a year now, and
did not see the FSM article referenced. There are a few points which
I'd like to add (pardon if they were covered in the article):
-ALWAYS use distilled (deionized - DI for short) water for rinsing brass
and making chemical solutions. Some water (such as in my location)
contains enough minerals to mess up the processes.
-ALWAYS use rubber gloves when handling the brass up to the point when
the photoresist is dry. One fingerprint will ruin the photoresist
adhesion, and unless you are MUCH more coordinated than I am, you WILL
touch the surface of the brass, no matter how careful you are.
-DO NOT use a cleaner that contains chlorine or chlorides to clean the
brass. It will slowly react with the brass and make bubbles/porosity in
the photoresist coating.
After experimenting with pumice powder (which abrades will but is very
hard to rinse all the particles completely from the brass surface), I
ended up using 3M brand "Scotchbrite" abrasive pads sold as a
non-metallic replacement for steel wool for fine wood finishing. I got
the dark maroon grade at a hardware store, and cut it up in 1 x 2 inch
(about 3 x 6 cm) pieces, and use one piece per etching session.
I also make up a very weak ferric chloride solution (maybe one part of
the etching solution to 100 parts of DI water) to chemically
clean the part after mechanical cleaning. My cleaning regimen is thus:
=1= Put on the rubber gloves.
=2= Scrub both sides of the brass under running water using the
abrasive pad (tap water is OK for this step).
=3= Squirt off the piece thoroughly with DI water from a spray
=4= Using plastic tweezers, dip the brass sheet in the weak acid
solution for 10 seconds or so.
=5= Thoroughly squirt off the piece again with DI water.
=6= Shake off most of the water, rub off most of the rest with a
paper towel (don't try to dry completely with the towel; it will
leave similar to water marks on the surface), and dry completely
with a hair dryer on low setting. If you leave too much of the
water on the surface (even DI) before blow drying, it will leave
water marks on the brass.
=7= Coat with photoresist as soon as possible (within 10 or 15
minutes for best adhesion).
Actually, after trying for a few weeks with the spray-on liquid resist,
I was unable to get an even coating across the whole sheet, no matter
how flat the sheet seemed. GC Electronics (who sell photoresist, along
with the ferric chloride solution) suggested spraying both sides of the
sheet, hanging vertically until dry, then spraying the sheet again and
hanging vertically again, but "upside down" from the first step. The
theory is that the coating will form a thin wedge, with the thickest
coating at the bottom of the sheet. When you spray again and invert the
sheet, the second wedge compensates for the first one. I never got it
to work to my satisfaction (one of my projects is N-scale [1:160]
railroad passenger cars with a ribbed outer surface, with .006" (.15mm)
ribs separated by like spaces), and ended up using dry film photoresist
made by Morton Dynachem.
This material is .001" (.025mm) thick, and covered on both sides by a
clear cover sheet. You take off one cover sheet and laminate the resist
onto the brass with heat and pressure. I bought a surplus Canon fuser
unit (like in a photocopier) that works perfectly for this function. It
actually took a bit of experimentation to get bubble-free, wrinkle-free
lamination, but I can coat up to .025" (.60mm) sheet this way.
I also progressed through the static (no circulation) etching bath,
through a bath with an aquarium heater and recirculating pump, to a
homemade spray etching tank, made from acrylic (Plexiglas, Perspex)
sheet with a small laboratory pump and two plastic spray nozzles that
mist both sides of the vertically-suspended brass sheet, and the
aquarium heater. I had known that commercial photoetchers use spray-type
units, and decided to try it out myself, but was not prepared for the
major leap in etching speed.
Apparantly, even with agitation in a submerged bath, a thin layer of
acid-with-etch-byproducts clings to the surface of the brass where the
etching is taking place, whereas in a spray unit, there is a continual
supply of fresh solution, together with a continual washing away of the
byproducts (which are then evenly dispersed through the etchant).
I had been diluting the GC ferric chloride by 1/3 with DI water upon
their suggestion (this moderately slows the etching but gives a smoother
etched surface) and it would take about 1-1/4 hours to etch through the
.025" (.60mm) sheet, working from both sides. This was with heating the
bath to about 100oF (40oC). With the spray tank, this same
concentration ate through the same brass in about 25 minutes. I now
dilute the ferric chloride by 1/2, and it takes about 30 minutes for the
I suspect that a mist-type spray bottle (with no metal parts [yes,
ferric chloride will attack even stainless steel, although slower])
might work well for applying the ferric chloride, for someone with the
patience to spritz the brass every 10 seconds or so.
If you are etching from one side only you can economize on resist by
coating the back side of the brass, after cleaning, with lacquer. If
you do coat both sides of the brass with resist (and are using the type
that remains where exposed to light) remember to expose the back side
[A] email@example.com (Frank Henriquez 4/95)
In article <firstname.lastname@example.org>, Scott Kirkham
> I use Radio Shack computer board etching fluid for making custom
> photoetched stuff.. Highly caustic stuff, but it works pretty well.
The Radio Shack etching fluid is Ferric Chloride, a truly nasty, expensive
chemical. It stains just about everything, and it's very difficult to
control the etching process (since it's an almost opaque liquid). It's
also very hard to tell when the Ferric Chloride is "used up".
A far better "solution" is to use Ammonium Persufate. It's very, very
cheap - a 5 lb jar of the crystals is roughly $20; Ferric Chloride
crystals are at least 3x - 5x more expensive. Ammonium Persufate maskes a
clear liquid that slowly turns blue as it dissolves the copper/brass. It's
very easy to control the etching process, and Ammonium Persufate doesn't
have to be heated for best etching (Ferric Chloride should be heated to
around 100F for best results). It's still a dangerous chemical, but not as
toxic or dangerous as Ferric Chloride. Most chemical supply houses will
have Ammonium Persufate; use it. Take the Ferric chloride to a hazardous
liquid waste disposal site - it just isn't worth the bother.
> the special Radio Shack resist pen, available at finer Shacks in your
> part of the world, and drew the artwork I wanted. Draw it a few times
> until you get what you like. Then cut it out, leaving a small border of
> raw brass around the edges.
Most of my etching has been to make printed circuit boards, but the
process of making photoetched parts is the same. I use a laser printer
friendly "paper" called Press N' Peel Blue. It's a thin plastic sheet, 8
1/2" x 11", coated with a flat blue material. You put the PNP Blue in the
printer and print your design; the toner sticks to the flat blue surface.
Next, you place the brass (or copper) material on a heat resistant surface
and the PNP Blue sheet on top of the brass, with the design facing, and in
contact with, the brass. You then use a regular household iron to IRON the
design onto the brass - it takes a few minutes, but the toner heats up
more than the surrounding blue material, melts and sticks to the brass.
The result is a brass sheet with your design in blue (the toner peels off
the blue material, which acts as a tough resist layer to protect the
toner). Next, etch the brass in the Ammonium Persufate. You may want to
use masking tape on the unused areas of the brass sheet, and on the
backside, if it doesn't have a design. You don't want to eatch more
brass/copper than you need to!
After the brass has been etched, remove the brass from the etching
solution, rinse it off and use it. The blue backing and toner are pretty
hard to get off; I usually scrub it off my PCBs with a copper and brass
cleaning powder (or similar abrasive cleanser) and it takes quite a bit of
work. It's probably best to leave it on delicate photoetched parts, or
look for a solvent that'll remove the toner and backing. Since most toners
are plastic, maybe a solvent like laquer thinner would work...haven't
tried it, though.
Press N Peel is pretty expensive; about $30 for 20 sheets. The company
that sells the material is:
Techniks Inc. PO Box 463 Ringoes, NJ 08551 (908) 788-8249.
Their ad is on page 111 of the April '95 issue of Nuts & Volts. They also
sell a material called Press N Peel Wet that can be used to make decals
(they show how in their instruction sheet). I did a test by scanning in a
decal sheet from a 1/72 scale Hasegawa kit and printing it (in black) on a
printer. The results were dissapointing - even at 600dpi, the laser
printer (and scanner) just didn't have the resolution to capture all the
fine details of the original. This is a problem with photoetched parts,
too. Don't expect to catch the fine details of a commercial photoetched
part. For instance, forget about reproducing an instrument needle in the
dial of a 1/72 scale instrument panel.
Larger scales probably wouldn't have this problem, though.
Hope this helps.
BTW - if anyone out there has used the Press N Peel stuff * AND KNOWS OF A
CHEAPER SOURCE OR EQUIVALENT * please let me know!
[Q] Are there any better etchants than the messy ferric chloride stuff?
[A] email@example.com (James T. Bober 7/95)
The best etchant I've found is based on perchloric acid and ceric
perchlorate. It is available from GFS Chemicals in Columbus Ohio as
product # 5910. Price is $25.50 for 4 liters.
rec.models.scale FAQ, part 7
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