Loc The alPhoto Etching by Glyn Thomas Part 1 – Introduction and Artwork I first became interested...

THE LOCAL/MID-EASTERN REGION/NMRA 1 MARCH — APRIL 2019

The

LocalA PUBLICATION OF THE MID-EASTERN REGION OF THE NMRA

Volume 74 March — April 2019 Number 2

Glyn Thomas is our newest MMR.

Glyn is British. I met him at the 2017 MER conven-tion, saw this clinic, and thought “we need this in TheLOCAL.” So I asked him later to write it and sendit...a little overdue getting published, but that’s moreabout the length than anything else.

This was written as a series, but the entire article ispresented here.


PhotoEtching by Glyn Thomas

Part 1 – Introduction and Artwork

I first became interested in photo etching living in England about 20 years ago. I’d used commercialetched detail parts and kits for several years before the British magazine, Model Railway Journal, ran acouple of articles on how to photo etch at home using a process designed for Printed Circuit Board pro-duction. I was in the middle of scratch building some coaches, and this appeared to be a good way ofcutting an accurate line of windows on the sides. I bought the materials and started to experiment. Mybiggest problem at the time was transferring the computer-generated artwork onto the metal, but I didmake some progress. Then I was offered the chance to move to America for work and shipping corro-sive chemicals across the Atlantic with my models was too high a risk, so I disposed of my materialsand the experiment was shelved.

Fast-forward to 2011 and another work assign-ment rekindled my interest in photo etching. I’dspent the intervening years building a large USlayout, but as it neared completion I accepted along-term assignment in Minnesota. We rentedout our house (with the layout locked in the base-ment) and moved to a small apartment overlook-ing the Mississippi. I refocused my modelingfrom the macro to the micro. About this time,MicroMark introduced their home photo etchingkit (#83123) and I thought it would be good tobuild a few small models to understand theprocess. Construction of my first model, adiminutive Minnesota Commercial railroad snowblower, was featured in Model Railroad Crafts-man in December 2013. That could have beenthe end of the story, but photo etching maintainsan enduring appeal for me due to the near-magi-cal way that fully formed components appearfrom the bare metal. Over time I’ve found that Iuse photo etched components in nearly everyscratch built model I make.

The purpose of this article is to introduce the photo etchingThe author, ready to etch.

Or fight off the zombie apocalypse.


process with the objective of proving that it iswithin reach of modelers who scratch build. I’llnot explain the production with step-by-step de-tail, since the MicroMark instructions do this well,but I will point out some lessons learned that gobeyond the basic process steps. In the remainderof this first article, I will explain how I produce art-work for my etchings.

The first step that is required is to produce someartwork. There are many ways to do this, and I’msure it is possible to do it with a draftsman’s penand a photocopier, but most people these dayswill start with a computer and printer.

You will need a good drawing package to produceartwork on the computer. A package that pro-duces raster graphics rather than vector graphicsis preferred, since you will need to manipulate in-dividual pixels. Personally, I prefer GIMP(www.gimp.org) for this process, because it ispowerful, free, and available on both the PC andMac. The only disadvantage with GIMP is that it isfairly complex and will require some practice be-fore producing good results. However, any prac-tice will be repaid many times over by the abilityto produce custom designs “on demand”.

When using GIMP, it is important to become fa-miliar with layers. These are best understood asbeing analogous to layers of tracing paper placedon top of each other over a physical drawing. Istart by creating a new document, usually 8 ½” x11” letter size, at 300 dpi resolution. The firstlayer is a background of white, the size of theoverall page. Then I’ll load a scan of an actualplan e.g. a side view of a locomotive as a secondlayer, and scale it to HO scale. I then create a thirdlayer for my etching artwork. Drawing on the art-work layer, I trace out the parts I want to etch (e.g.the cab side) using the stroke tool – I usually setline width to 2 pixels, and disable antialiasing toavoid any grayscale pixels. Elsewhere on thepage, I create a bounding box of 3” x 3”, which isthe maximum size the MicroMark etching systemcan etch, and move my tracings into this area asthey are completed. Once the box is close to

being full, I draw bounding boxes around thecomponents, and use the flood fill tool to paint theintervening space black (this will be the materialremoved during etching). Any voids in the com-ponent itself, such as cab windows, also need tobe filled black. Then I’ll copy the entire etchingbox, and flip it horizontally to create a back-to-front image – this will be used to mask the otherside of the etching. I draw tabs on one side onlyto hold the fret together – I use 7 pixel white lines,but these often etch through on a typical run, soyou may prefer to use heavier lines. You can alsoadd fold lines on one side using 3 pixel black lines,to make it easier to fold up parts that representmultiple sides in the final etch.

When I’ve completed the etch design I hide theplan layer, and the work is ready for printing andtransferring to the metal.

The LOCAL has run articles about GIMP before. Itis exactly as Glyn describes. Powerful, but not triv-

ial to learn and use. Well, same with Photoshop.

Figure 1 – There are 18 homemade photo etched partsin this photo, including windows, bench, water wheel

details, tie rods, and sluice mechanisms.


Figure 2Creating a new

document inGIMP at 300 dpi

resolution.

Figure 3A plan has

been loadedas a separate

layer andscaled to HO

scale


Figure 4 – Tracingthe side tanks of

the plan on a sepa-rate layer, using the

Stroke tool.

Note 2 pixel widthand no antialiasing

Figure 5 – Drawa 3” x 3”

bounding boxelsewhere on

the sheet,using the

Stroke tool


Figure 6 – The tankdesign has beencompleted (includ-ing top, sides, andrear, to be folded)and transferred tothe bounding box.An outer box hasalso been drawn.

Figure 7 – Thespace betweenthe outer boxand the tank de-sign has beenflood filled withblack and tabsadded with thepencil tool


Figure 8 – Use copy-paste to create acopy of the design,then flip horizontalto create a reversedcopy

Figure 9 – In the final design, the reversed copy has tabs and fold lines re-moved (they will etch half-way)


Part 2 – Transferring Etching Artwork to Metal

In this second section, I’ll discusssome potential uses of photo etchedcomponents, and how to transfer art-work to metal.

Many modelers will have already usedphoto etched components. They areoften provided as details for craftsmankits, or can be bought as individualparts to enhance existing models, e.g.the very fine Plano Model Productsetched walkways for freight cars.

The primary materials that can beetched are brass or stainless-steelsheet. The MicroMark kit will easilywork with either 0.005” or 0.01” thick-ness material. 0.005” material is use-ful for non-structural detail parts, andcan be used for small structural com-ponents if folded or laminated in lay-ers. I’ve used it for many projectsincluding:

WindowsWhen I built my large layout, I constructed 30-40 structures from scratch, mainly usingGrandt Line windows and door castings. I can now spot these components on other people’slayouts from about 20 paces. Therefore, to make my structures more individual, I now etchmost of my own windows

HandrailsSignal partsNon-functioning mechanicalcomponents, such as gears,levers, and hand-wheelsLaddersStreet furnitureCab and car sides.

0.01” material has good mechanicalproperties and can be used stand-alone for structural components. Ihave used this for a freight carspringing system in brass, and lococoupling rods in stainless steel.

Figure 10 – Printing the design created earlier. Make sure the scale is 100% and 300 dpi.

Figure 11 – The purpose of this stage is to attachphotoresist to the metal and then sandwich the re-sult in a negative. When exposed to the light, thephotoresist will harden where the negative is clear.


Stainless steel is useful for its strongermechanical properties and the attrac-tive high shine that remains even onsmall scale components.

If you followed the steps explained inpart 1, you should have some artworkthat is ready for etching. The next stepis to transfer the design from the com-puter to metal. This is achieved by at-taching a special material, photoresist,to the metal, and then printing the de-sign onto the photoresist.

I start by printing my design from GIMPonto MicroMark Inkjet Film (#83128),making sure to keep the scaling at 100%and setting your printer to print at BestQuality Photo Paper. A single sheet ofthe Inkjet Film will take three 3” x 3” de-signs, so if you are frugal, you maywant to wait until you have that manypieces to etch. Alternatively, partiallyused sheets of inkjet film can be re-tained and used for future printing. It isimportant to print on the matt side ofthe film, because the ink won’t adhereto the gloss side.

Taking the printed film, I then cut outthe 3” x 3” front and reverse patterns(with about ½” of extra sheet allaround) and place them together withthe matt faces inwards. The patternsare aligned and then the patterns aretaped together to form a sandwich thatwill enclose the metal sheet to be etched.

For the next few steps, it is necessary to prepare the workspace in advance. I partially blackout a part ofthe room that has access to running water (in my case, the WC that adjoins my railroad room), andplace tools that I will need there – scissors and tape, plus the lightproof bag of photoresist, the Plexi-glass sheets, and clamps from the MicroMark etching set. At this time, I also usually plug in the Micro-Mark laminator to allow it to heat up.

I then prepare the metal in the lit part of my workspace. I cut a 3” x 3” sheet of the required materialusing tin snips. The metal needs to be burnished in order to achieve good adhesion of the photo-resistmaterial. Burnishing is achieved by rubbing vigorously with a dampened metal preparation pad (Mi-

Figure 12 – Using the metal preparation pad to burnish the metal

Figure 13 – The two sides of the negative needto be aligned and taped together


croMark #83134). This doesn’t need tobe over the top – about one minute perside is sufficient.

The purpose of applying photoresist isto protect the parts of metal that wewant to keep when we etch our artwork.Photoresist is a material that hardenswhen exposed to ultraviolet light, andwhen hard cannot be dissolved by thecorrosive acid used for etching. Micro-Mark’s photoresist (#83130) is providedas rolls of the active material, protectedwith a thin plastic film on front and rear.To apply the photoresist, I move to thepartially darkened room. I open the bagof photoresist material and cut two 3” x3” squares. Using tape, I remove theinner protective film from the photore-sist, wet one side of the metal, and thenslide the photoresist onto that side. Ithen repeat the process for the otherside. The photoresist needs to bebonded to the metal by passing bothsides through the laminator on itsheated setting. MicroMark providesthin waxed card (#83129) to place aboveand below the work as it’s passedthrough the laminator, and this is rec-ommended in order to avoid damagingthe photoresist layer (BTW, plain paperdoesn’t work for this purpose!)

While still working in semi-darkness, Isandwich the prepared metal betweenthe patterns and clamp it between plexi-glass sheets.

Now it is time to expose the work to ultraviolet light. This can be achieved simply by taking the workoutside on a sunny day. In summer midday sunlight in Philadelphia, an exposure of about 2 ½ minutesper side is usually adequate to print the design. Working later in the day, during other seasons, orhigher latitudes will increase the exposure. It is virtually impossible to print on a winter overcast day inMinnesota regardless of the exposure (I know!). It is usually possible to detect hardening of the pho-toresist because it will turn light blue due to the light even before the development stage.

The work now needs to be developed to remove the unexposed (clear) photoresist. This is necessaryso that the etching acid has access to the metal in the appropriate places, and it also halts any further

Figure 14 – Photoresist has been cut and the inner pro-tective film removed. It is then temporarily attached tothe metal with a film of water. Using the heated lami-nator, the photoresist is bonded to the metal.

Figure 15 – Exposing the design to sunlight.Approximately 2 ½ minutes per side is re-

quired in bright sunlight as shown here


printing on the metal due to light exposure. Return-ing indoors, I put on surgical gloves so I can workwith the developer. I remove the treated metal fromthe pattern sandwich. Then I use tape to remove theouter protective film from the photoresist on bothsides, and develop the result using diluted photore-sist developer (#83127.) This is a critical stage andrequires careful timing of about 20 seconds per side.I occasionally remove the work from the developer,rinse off, and brush over with an old paintbrush. Theeffect to aim for is a slight embossing of the blue(hard) photoresist, with no residual clear (soft) pho-toresist. Care is required to avoid lifting the hard-ened photoresist, but if bubbling occurs, it canusually be arrested by quick rinsing. The resultshould be a piece of metal sheet with the designclearly visible in blue on both sides. If the design isnot visible, then strip the photo-resist and repeat.

Part 3 – Etching the Metal

Before describing the etching process, it is necessary to talk about safety. The etchant used is FerricChloride (MicroMark #83126), and this is harmful if it gets on exposed body parts. In particular, it isnecessary to protect eyes from splashes and spills, so use eye protection whenever handling the fluid.MicroMark provides ap-propriate goggles in theirkit. It is also necessary toavoid exposed skin, souse a protective cloakand gloves – again, theseare included in the Micro-Mark kit. The gloves aresingle use, so buy a boxof surgical gloves fromyour local pharmacy(these are also very use-ful for other messy mod-eling processes, e.g.handling paint). Further-more, the fluid will causeindelible stains on metal,wood, fabrics, and ce-ramic surfaces, so makesure the workspace iswell covered. Since theprotective gear can be

Figure 16 – The exposed metal is de-veloped to remove the clear (unex-posed) photoresist. Be careful to notover-develop and remove the blue(hardened) photoresists.

Figure 17 – When the metal is immersed in etchant, it willbe corroded away where not protected by photoresist


bulky and restrict motion, it is worth clearing fragile items, suchas work-in-progress models, from the workspace to avoid inad-vertent damage. Finally, make sure that your workspace is wellventilated to avoid buildup of fumes.

The MicroMark kit comes with a plastic etching tank with workclamp, and a fish tank aerator that will agitate the etchant. I fol-low the MicroMark instructions in preparing the work area, witha bucket of water for rinsing work, and another that can be usedto rinse any spills. I heat the etchant by placing the MicroMarkcontainer into a bowl of hot water. Then the tank is filled andthe agitator started. The previously prepared metal is attachedto the clamp and lowered into the tank. Every five minutes orso, I remove the work from the tank and rinse it.

Although this is a protracted process, it is very satisfying. Evenfrom the first 5 minutes, you will start to see definition on thedesign where the etchant is dissolving the metal. Soon after-wards, you start to see holes all the way through the metal.Eventually, the holes link together and you see the fully formedparts.

One of the challenges with the process is differential etching. Typically, items towards the center of theworkpiece will etch faster than those around the edges. I found that using relatively small tabs on thework means that fully etched parts can besnapped from the etch during the rinsingprocess, and this will avoid over etchingthese parts.

Typically, 0.005” brass will take about 20minutes to etch through with fresh etchant.Times will increase with subsequent repeatusage, and I usually replace the etchantwhen I hit about 40 minutes per etch – in myexperience this is equivalent to 8-10 pieces.I make a note of etches and times on theetchant bottle to track usage.

With the piece fully etched, I clean up myworkspace. I remove the remaining pho-toresist from my etched parts using undi-luted developer and I’m ready toincorporate the parts into my models. Forpainting, I’ll usually use a spray primer,such as Tamiya Primer, followed by an air-brush of the appropriate finishing color.

Figure 19 – I heat the etchant by put-ting the bottle in a bowl of hot water.(Heat makes chemical reactions gofaster, but can be dangerous.)

Figure 20Pouringthe etchantinto theetchingtank


One of the biggest improvements I made in theprocess over time was create small batches. Theartwork can be produced at any time, but thereare benefits to batching the transfer of artwork tometal, and the etching itself. If you have severaldesigns ready to transfer to metal, it’s easier usethe whole sheet of the inkjet film. You also savetime on setup, and this process can be saved for abright sunny day. Once designs have been devel-oped, they are stable for a long time withoutneeding to go directly to etching. I tend to do theetching itself on evenings where I have nothingelse to do and my wife is out at social events – ifyou have 2-3 hours free, it’s possible to getthrough a number of etches in a single night.

Overall, the process is complex, and you willmake mistakes, especially the first time through.One difference from regular modeling is thatthere is little benefit to “falling forward” i.e. con-tinuing when a problem arises – better to stepback and redo the current stage. This is funda-mentally a reproduction process, so it’s alwayspossible to go back and redo work. The one areathat may not be reversible is safety, so PLEASEBE CAREFUL.

I hope that this series of articles will encourageothers to try this fascinating process. I have pro-vided a sample design that can be photocopiedby anyone who wants to try this out (non-com-mercial use only, please!)

NOTE: I have frequently referenced MicroMarkproducts in this series. I have no link to Micro-Mark apart from being a satisfied customer.

Figure 21 – I’veremoved a par-tially etchedpiece from thetank for rinsing

Figure 22 – The work is rinsed in a bucket of water


Figure 23 – The agitatorbubbles air through theetchant during etching

Figure 24 – Etching iscomplete, some partshave come loose in thefinal stages of theprocess


Figure 25 – Undiluted developer isused to remove the photoresist

Figure 26 – Street furniture design – try it at home!

Figure 27 – The final artwork forthe table and chair above. Packthe art in tight and make morethan one at a time.

Published in The NMRA Magazine

Website: www.nmra.org

BONUS INFOAdditional Information About Photo Etching

From NMRA Member Nigel Phillips

Nice article on the Micro-Mark photo etching system by British modeler Glyn Thomas.

Anybody using the system needs to be aware of the requirement for proper safety precautions (waterproof gown and gloves, and eye protection, adequate chemical storage) as well as proper disposal of the used chemicals. Sodium hydroxide and ferric chloride are harmful and corrosive chemicals. The sodium hydroxide can usually be disposed of down the toilet, but the spent ferric chloride needs to be taken to the local dangerous chemical disposal facility. Before getting the kit, check where the facility is and whether it will even take these chemicals in small quantities. My local facility charges for this. The other thing to consider is the size limitation of the laminating machine and ability to handle various thicknesses of metal. Anything over 3 inches square and it’s a no go.

Those who wish to progress to “large” etches such as steam locomotive or tender frames, and tender sides and boilers in anything larger than N and small HO scale models need to look elsewhere. Getting all the bits and pieces is one way, (Micro- Mark does that for you as a kit. A visit to eBay or Amazon will get all the items needed for probably less.

If you have software that outputs in vector mode

such as Adobe Illustrator, CorelDraw or Autocad and you take the time to become familiar with layers (essential for half etching), then it actually becomes cost-effective to send out the completed artwork to an etching service. This is especially true if you do not have a good place to do the etching yourself. The kitchen is definitely not somewhere you want to do this, and I would even question the powder room if it’s used by anybody other than your modeling buddies. Cries of “what are these brown stains on the walls/floors/doors/toilet seat?” are not something you want to hear.

Commercial etching services will often handle prototype etches, use optimized etching conditions (high temperatures and catalysts), and can usually handle anything from brass alloys through steel at sizes up to 1 x 3 feet. The major cost in having a service do the etching is the artwork. If you can provide the front and back yourself it can cut the cost by 75%. Once the drawing is on file it becomes much cheaper.

If you only need etches a couple of times a year, or need a large number of repeat etches, a commercial service can be a cost effective alternative. And a lot less messy, especially if you weren’t planning on redecorating the powder room and replacing the sink and toilet anytime soon!

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Loc The alPhoto Etching by Glyn Thomas Part 1 – Introduction and Artwork I first became interested...

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