Etching Brass on the Cheap

[CWJ]

My current project to build a Class 325 Royal Mail EMU (http://www.rmweb.co....__fromsearch__1) requires some scratch-built detailing parts which I would like to etch from brass sheet. These small parts don't justify a large amount of effort or cost, so I decided to try a method which didn't involve teaching myself to use a CAD package or paying a specialist firm to do the etching. I was inspired by Nigel Lawton's online guide (http://www.nigellawt...s_Version_5.htm) which makes it all sound very achievable - in fact I have shamelessly copied Mr. Lawton's method and make no claims for originality of the ideas!

 

I will attempt through this thread to briefly illustrate the process I have followed, rightly or wrongly; for full details of how to do it properly, please see the above website. Basically:

1. Design the artwork on the computer using bog-standard Microsoft Office software*
   
2. Print a mirror image of the artwork onto overhead projection acetate sheet, using a laser printer
   
3. Use a domestic iron to transfer the toner pattern from the acetate onto the brass sheet
   
4. Submerge the brass sheet into some ferric chloride (a corrosive chemical) until the exposed brass is etched away but the parts protected by toner remain intact.
   

...and that's it! This method is a bit 'rough and ready', but it is more affordable than professional photo-etching because it misses out the photo-development of the etch resist and doesn't need any specialist equipment.

 

Cheers,

 

Will

 

* I know that some CAD users will wince at the idea, and having struggled with some of the MS drawing tools I can understand why, but for all their limitations they are at least familiar to me - learning to use a CAD package would take me longer than the whole process above.

[coachmann]

The ferrick chloride process is famiar to me as it was used at GEM in the 1970s. Casting thickness brass coach sides were prepared by the resident pattern maker and the back and edges sprayed with paint. Then I hand ruled on the 'raised panelling' in black cellulose (not sure now whether they were IOM or FR coaches). The sides were left in warm ferric chloride until the panelling was in sufficient relief and then washed. Rough & ready as you say but job done.

 

In the 1990s I prepared artwork on cardboard in the usual red & black 7½ times larger than the finished product. It has a lot going for it when parts are small (I produced a range of bus radiators in 4mm and 1/50th scale) but it's combersome with 4mm coaches even 3 times larger than 4mm scale.

 

I agree CAD isn't for everybody...I never bothered to learn. But if you can find someone to design on CAD, some etching firms will produce as small a sheet of brass as you require.

[sej]

Fantastic! I'm fascinated to know how this turns out for you. If I get a moment I'll have a go too and let you know.

Cheers

Simon

[CWJ]

1. Producing the Artwork

 

A very useful guide is available from Hollywood Foundry (http://www.hollywood...and%20Rules.pdf) which tells you everything you need to know about designing artwork for metal etching, and wider guidance is also available from the same website. I used this, along with some other online guidance from commercial etching firms, to make myself a brief set of 'rules' as follows, where 'T' is the thickness of the metal to be etched:

• General Compensation for Cusping (Double-Sided Etch) = 0.2 x T (note: for a hole or slot, double this to account for cusping on both sides of the hole or slot)
• General Compensation for Cusping (Single Through-Etched) = 0.4 x T (note: for a hole or slot, double this to account for cusping on both sides of the hole or slot)
• Minimum Diameter of Hole = T
• Minimum Rivet Diameter = 1.4 x T (for best definition of half-etched rivets)
• Dimple Diameter for Punched Rivets = T
• Minimum Width of Raised or Sunken Line = 0.8 x T
• 90 Degree Fold Line Width = T* (etched on inner face of fold)
• 180 Degree Fold Line Width = 1.5 x T* (etched on outer face of fold)
• Gap Around Etched Parts = 2 x T
• Fret Tag Width = 1.5 x T

* to be added to overall dims of material, not just drawn on

 

The design was drawn up in Microsoft Powerpoint, as I found this had the least amount of irritating automation (MS Word was the worst ). This was converted to a PDF file as I needed to take the file to work to print on the laser printer, and I didn't trust Microsoft to keep the drawing identical when opened on a different computer. Please see attached file if you're interested in the etch, but unless you're into EMUs this is unlikely! It includes a bogie frame (with fold-up brackets for the axle bearings, brake cylinders and square flaps to represent the traction motors), a pair of cab doors, an NRN radio aerial and roof bracket. Note that the artwork is in two mirrored parts; these will be folded around the brass so that each part is transferred to one side of the brass. Where the two parts are different, only one side of the brass will be etched (i.e. half-etched).

 

As mentioned above, this was printed onto overhead projector acetate transparencies using a laser printer, scaled to actual size. I added a 200mm line to check that the print-out was correctly scaled.

 

Cheers,

 

Will

 

Class 325 Detail Etch.pdf

 

Edited March 2, 2023 by CWJ
Restoring attachment.

[CWJ]

3. Transferring the Printed Graphics to the Brass Sheet

 

Right, that's the easy bit sorted - now the fun and games start!

 

The brass is slotted between the folded transparency so that the graphics are aligned with each side of the sheet, but there are two ways of heating everything up so the toner transfers to the brass. Nigel Lawton recommends a domestic iron, but another source used a laminating machine as these have a hot roller. The latter sounded easier, so I tried it, but unfortunately even after two or three passes it became apparent that the acetate was not going to part with its toner. I then got the iron out and set it to a medium heat. It took quite a long time for the toner to transfer to the brass, and I had to apply a lot of pressure to all parts of the sheet. This left the acetate stuck to the brass, so I had to carefully peel it away. The results are as below:

 

 

 

Not bad for a first attempt, I suppose, but it isn't good enough to use. There are a lot of 'bubbles' where the toner hasn't stuck to the brass, but what you can't see on this photo is how the edges are not very well defined - it looks as if the toner has completely melted so the graphics are not sharp enough. Small details such as rivets aren't visible at all, and neither are some of the half-etched fold lines.

 

I attempted to tackle these problems in two ways. To get the toner to 'stick' I rubbed down the brass with 200 grit wet and dry so it wasn't as polished as the first attempt, and to improve the 'sharpness' I decided that one short burst of heat might be better than messing about with the laminator and medium iron. I therefore set the iron to just below full power and had another go:

 

 

 

This is much better - all the fold lines are visible, and even the tiny screw heads along the bottom of the cab doors. Most of the imperfections could be touched in with a marker pen or even paint, but unfortunately this would be impossible on some of the smaller details, which were worse on the other side of the brass than this side. I had printed three copies of the artwork, so I had one more chance to get it right this afternoon...

 

 

 

...oh well! The third attempt was not quite as good as the second, with a lot of toner missing around the cab doors and slightly smudged edges where I must have let things get too hot. I had dispensed with the tea towel I was previously using to protect the acetate from the direct heat of the iron, so perhaps it would be best to re-instate this.

 

That's as far as I've got at the moment, but I'll keep trying until I get it right. It may be that a different type of transparency will 'let go' of the toner more readily.

 

Cheers,

 

Will

Edited March 2, 2023 by CWJ
Restoring photos.

[CWJ]

Then I hand ruled on the 'raised panelling' in black cellulose (not sure now whether they were IOM or FR coaches).

 

Judging by my photos above, I could do with your assistance Coachmann!

[CWJ]

4. Etching the Metal in Ferric Chloride

 

Following Nigel Lawton's guidance I have knocked up a basic bubble etch tank, where air is blown through the acid to agitate it in a more consistent way then stirring. Everything must be made from plastic or glass; metal and other materials will be corroded by the ferric chloride. Here is the general set-up:

 

 

 

An old air compressor (pump) from a fish tank is connected to a short hose leading to my etching tank, which is in fact a food container with clip- on lid so I can use it to store the horrible stuff safely. The hose will be taken out and stored in clean water.

 

 

 

At the bottom of the tank is a 'bubble curtain' - a piece of hose with lots of tiny holes in it. This was supplied (from an aquarium shop) with clip-on suckers which are useful for attaching it to the tank.

 

 

The tank was filled with water to test the bubbles. Very pretty!

 

 

When I finally get the etch-resist (toner) correctly printed onto the brass, I'll be ready to start etching.

 

Cheers,

 

Will

Edited March 2, 2023 by CWJ
Restoring photos.

[PhilH]

Just a note of warning - as part of my job I deal with (highly concentrated) ferric chloride on a daily basis - IT IS NASTY STUFF. Please take all necessary precautions, especially eye protection. It will also permanently dye anything it comes into contact with.

Edited March 27, 2012 by PhilH

[Jol Wilkinson]

MRJ has also featured articles on "home" etching, in issues 57, 190 and 193. The last, by John Mcrea, used a similar system to that you have set up. I believe he is still developing his approach.

[ianmaccormac]

This looks like a good start but its not that expensive to use an etcher like PPD.

They will accept the drawing as non-layered artwork as the pdf you ave, you could send it by email.

They will take that and produce it in the thickness of brass or whatever you want for a very reasonable price.

I am a satisfied customer, but used to fiddle with the etch tank from pcbs and only got 'acceptable' results from home etching.

They have a price guide on their site and you don't have to make your own tank, dice with an iron, get the orange stain from the ferric chloride in places

you don't want it or use acetates at work etc etc.

Whilst I love to see experimentation, this is starting to require all sorts of things to be made when, for probably less price, you could have

the thing professionally etched.

Incidentally, put the etch tank in hot water as it will etch quicker when warm.

Good luck

Ian

Edited March 27, 2012 by ianmaccormac

[N15class]

Very interesting I have often thought about etching, it could possibly be even more relevant now I am in Brazil. Looking forward to seeing more.

[RedgateModels]

hmmm, I need a couple of PCBs etching for Fourgig, wonder if this method would work, I have the artwork reversed already and plenty of lazer acetate ....

[CWJ]

Thanks for all your responses! Now I know so many people are watching, I'd better get a move on

 

Just a note of warning - as part of my job I deal with (highly concentrated) ferric chloride on a daily basis - IT IS NASTY STUFF. Please take all necessary precautions, especially eye protection. It will also permanently dye anything it comes into contact with.

Thanks Phil, you're absolutely right. I have only used the stuff once in the past and I vividly remember everything in the vicinity becoming brown. I will try to show the safety precautions I take as I go along. For a start, one of my photos above shows my etching tank sitting on a large plastic tray to contain any spillages.

MRJ has also featured articles on "home" etching, in issues 57, 190 and 193. The last, by John Mcrea, used a similar system to that you have set up. I believe he is still developing his approach.

Thanks for the tip-off, I'll look out for old copies of MRJ!

This looks like a good start but its not that expensive to use an etcher like PPD...

Incidentally, put the etch tank in hot water as it will etch quicker when warm.

Good luck

Ian

Thanks Ian! If (or should that be when?) I get fed up with experimentation, which I never expect to produce professional results, it is very helpful to know that there are affordable suppliers out there. For anyone who's interested, this is the website that Ian recommends: http://www.ppdltd.com/ There is very some useful information on there.

Very interesting I have often thought about etching, it could possibly be even more relevant now I am in Brazil. Looking forward to seeing more.

Hello N15, you might not have much choice unless you know of a local etching firm! Remember this is pretty much the same process as PCB manufacture so an electronics supplier may be flexible enough to etch metal parts for you.

hmmm, I need a couple of PCBs etching for Fourgig, wonder if this method would work, I have the artwork reversed already and plenty of lazer acetate ....

You won't know until you try, Redgate! I guess PCBs would be slightly easier than solid metal parts, too. Alternatively, there are many mail-order companies who will etch PCBs for you in return for the graphics in their preferred format (and some money, of course!); I once had some 2-sided PCBs made by an American firm who did a fantastic job with printed labels and protective varnish. These luxuries aren't essential for model railway use though.

 

Cheers,

 

Will

[RedgateModels]

Just spotted this at Maplins

 

http://www.maplin.co.uk/pcb-etch-powder-47464

 

for a quid it's a no brainer, will be picking some up on my way home tonight

[stadman]

Saw this a while back http://hackaday.com/2009/07/13/etch-pcbs-with-ferric-chloride-and-a-sponge/ May be of use?

[CWJ]

Thanks for the suggestions chaps. I have already got some ferric chloride granules but the Maplin product is very (unusually for Maplin...) reasonable. As for the second suggestion, this sounds much easier although I dread to think what the acid does to the sponge! You must have to check that the sponge is resistant to the acid before starting.

 

I've printed out a few more copies of my artwork today, so I'll have another go at transferring it to the brass tonight or tomorrow. Making progress is frustrating at the moment as I'm working away from home a lot, but I'll get there eventually...

 

Cheers,

 

Will

[Guest]

I did a little bit of etching some 20 odd years ago using Kodak resist KPR3 I think it was. I actually built an etching tank from plywood and painted the inside with glass fibre resin. There were two paddles approximately 6 inch diameter mounted on a horizontal shaft with bearings either side and motor and pulley mounted outside. Ferric Chloride level was kept well below the bearing height for obvious reasons. I probably did a dozen or so paneled coaches plus other odds and sods. One thing I did notice is that etching was quicker when the surface of the brass is splashed.

 

As the ferric chloride cooled and the etching process slowed down, I would add some ferric chloride crystals which would raise the temperature of the mix. I did think about adding a fish tank heater but never got round to trying that.

 

I used ajax for cleaning the brass. Hold the brass sheet under running water and check for greasy areas.

 

Hope this is of some help.

Edited March 29, 2012 by Guest

[stadman]

I have used an old photo developing tray for etching (Plastic)

[CWJ]

Thanks chaps, all good advice and much appreciated. A common theme is that a constant supply of fresh etchant needs to be flowing over the metal, by whatever means possible.

 

Have had several more goes at transferring the toner to the brass, and not managed to get anything better than the photos above. I'm going to have to try a different type of transparency or even the photo paper method... the difficulty with the latter will be lining up the two patterns for the front and rear of the sheet. This is easy with a transparency because you can add some alignment crosshairs to the print-out (see Nigel Lawton's website) and one pattern can be seen through the other. Mrs. CWJ suggested that if I was using paper I might be able to align the sheets by poking a pin through both sheets.

 

Watch this space!

 

Cheers,

 

Will

[ianmaccormac]

try lining up against a sunny window, almost looking into the sun, to see through them both and align, then glue them together. or staple or a bulldog clip. The laminate type of photo resist is good for coating brass, heated through a laminator

Cheers

Ian

[CWJ]

I've printed out a few more copies of my artwork on transparencies, photo paper and normal printer paper. Hopefully at least one of them will yield good results when tried tomorrow night!

 

Cheers,

 

Will

[CWJ]

I couldn't really improve on the etch-resist pattern achieved in the second photo of Post No.5, so I decided to take the plunge and have a go at etching with something of this quality. Any faults in the toner were touched in with a permanent marker until the everything looked as neat as possible.

 

I said I would describe the safety measures I'm taking. Ferric Chloride is corrosive, so it's important to make sure that it can't come into contact with any part of your body or any other property which you don't want to damage! I wore eye protection (plastic goggles), old clothing with full-length sleeves and latex gloves. The area was covered in an old sheet to catch any drips and the etching tank was placed on a large plastic tray so even if I knocked the whole thing over it wouldn't be a disaster. Here is the etching in progress:

 

 

 

As you can see, my brass fret isn't completely submerged - this was an oversight on my part; I hadn't taken into account the space taken up by the bubble tube at the bottom of the tank. Once the bottom part was etched, I had to turn it around and dunk the un-etched part in afterwards. This led to a region on the boundary of the two parts which was over-etched. This is the etch fresh out of the tank:

 

 

 

Apologies for the poor photo but this was taken hastily at a busy moment. It looks messy at this point but I was delighted that the etching process has basically worked! Next is how it looked after cleaning up:

 

 

 

There are two main faults with this. Firstly, the area which got etched twice has been over-done (see the cab doors and part of the bogie frame). Secondly, the etchant has got under the etch-resist in some areas and left a rough surface. The first defect is not acceptable so I'll need to ensure the whole thing fits in the etch tank next time, but the second one isn't as bad as it looks and doesn't matter on these parts. It would obviously be a problem if I were making something cosmetic such as nameplates. Here are the parts removed from the fret, quickly folded into shape but not yet soldered or glued:

 

 

 

 

 

And finally, the bogie frame shown with one of the cosmetic sideframes:

 

 

 

I didn't think that went too badly for a first attempt - I hope to be a bit neater with the next etch but I have a feeling that future etching requirements will be more easily done using a commercial supplier!

 

Cheers,

 

Will

Edited March 2, 2023 by CWJ
Restoring photos.

[CWJ]

I've just gone through the heart-wrenching experience of watching a long and carefully-composed post disappear into the information super-highway as RMWeb threw a wobbly, so apologies if this replacement entry is a bit abrupt!

 

After four goes at etching, I have found it better to use the waxed backing paper on which sticky labels are supplied as a means of carrying the printer toner to the brass. It 'lets go' of the toner much more readily than the acetate transparencies I had been using. Here is the first etch resist patter done this way:

 

 

 

The only significant issue is that the paper, when ironed, tries to wrinkle a little, resulting in the rough areas on the cab doors (top left of photo). And again after a generous amount of touching-up using a 'Sharpie' permanent marker:

 

 

 

After thirty-odd minutes of etching, here is the resulting fret:

 

 

 

I'm very happy with this - it isn't perfect (remember the photo is about twice the size of the real thing though!) but the parts are better than anything I could ever make using hand tools.

For interest, here are the parts after folding, soldering and cleaning-up:

 

 

 

I'm glad I had a go, as it's very satisfying removing the metal from the etching tank and cleaning it up to reveal a nice shiny fret. This process might not give you a perfect crisp etch, but it can clearly produce decent results for a fraction of the cost of a professional service.

That's all from me for the time being, please feel free to use this thread to post your own experiences of home etching, or to ask any questions. I probably won't know the answer but someone on here will!

Cheers,

Will

Edited March 2, 2023 by CWJ
Restoring photos.

[N15class]

They have turned out nicely. I assume that they have served there purpose.

[CWJ]

Thanks Peter! They have certainly come out at the right size and in reasonable quality, and you can follow my Class 325 thread if you're interested in how they look on the finished model (first link in Post No. 1 of this thread).

 

Cheers,

 

Will

Edited April 12, 2012 by CWJ