Iron-on PCB Etching Film

 

For the first time, I'm trying out some iron-on-peel-off PCB film for etching copper plaques.

As with any new thing, there are hiccups -- sorting out how to get it through my laser printer without jamming, for a start. And also, I forgot to reverse the text, so I'll have to do that one over.

Apart from those issues though, it looks like a useful tool. Now I just have to research how to get it off after the etching is finished.

Note: Acetone. Acetone whips it off easy-peasy. 

Plaque in Progress

 

Etching today.

I'm using Lascaux acrylic stop-out varnish as a resist to deep-etch a piece of approx. 2mm copper that will eventually be a plaque inset in a box top. The Lascaux is easily cleaned up with water while it's wet, and later on it can be removed with meths.

The mordant is "Edinburgh Etch", which is a combination of ferric chloride and citric acid. It's a lot safer on skin than nitric or hydrochloric, and it also bites fast and clean. Note: "safer" is a relative term; I still wouldn't go bathing in it.

It's a relatively warm day today, so I shouldn't have to go to all the faff of warming the bath. I'll probably have to etch for four to six hours to get the depth I want.

The tape is so that the back of the plate doesn't etch, and the chopstick rests on the lip of the mug to hold the plate vertical in the bath and to allow me to lift it out without touching it.

And now, six hours or so later, it's done.

The size is about 75 x 100 mm.

The etching really reveals the grain of the metal — not a grain in the way that wood has a grain, but gravity acting on the tiny granules of copper separated by the acid makes them slide down the face of the metal so the bite becomes uneven. There's also an element of uneven density within the metal itself, a relict of the way the sheets are produced in rolling presses.

Etching Press Modifications

A few years ago, after a small windfall, I bought myself this little intaglio press. It's sold by an Italian company called RGM, and it's fundamentally identical to the Fome portable press available from Jackson's. So similar in fact that I strongly suspect that they're all just pumped out of a factory somewhere in China and re-badged by the end sellers. It's a decent, fairly well-engineered, entry-level press that doesn't take up a lot of room, but it's not without its issues.

The hand-crank supplied with the press is just stamped from a sheet of mild steel, and it's not nearly strong enough. Mine started to bend when the press was under even moderate pressure. I replaced that with a cast iron pulley wheel taken from an old pump, and that works much better, although its spokes can interfere a bit with the pressure adjustment screw on that side.

The other major issue is the bed, which was just a piece of 270mm wide 3mm stainless steel. It was adequate, but the felts and paper and everything tended to slide on its surface when they came up against the roller. I replaced that with a piece of 12mm plywood, a bit longer than the original bed. The knurled lower roller grips the wood very positively, and the felts stay in place on top. There's a possibility that it may end up being warped by the pressure of the rollers, but if that happens it's a very cheap and easy thing to replace.

The third issue, and it's one that I don't think I can do anything about, is the diameter of the rollers. They're only 34mm in diameter, and ideally I'd prefer them to be at least double that. The small diameter means that there's quite a steep angle of attack when the roller meets the plate, which is not ideal. However, they do work, and the press will produce pretty good prints, up to about A4 in size.

Reference Prints

I've been organising my old intaglio plates, and part of that process is taking reference prints from each of them so that I can see what's what when the plates are wrapped up in acid-free tissue against corrosion.

I'm not agonising over them at all, since all they have to do is show me what the plate does. Some of them would do with some much more careful wiping out if I was doing prints that I actually cared about.

Something I need to arrange is somewhere where I can work safely and smoothly with acid, taking into account fume extraction as well as splashes and spills. I have some smallish photographic developing trays which will do to do the etching in, and I can create an acid-proof work area easily enough with plastic sheeting, but fumes are something a bit trickier to deal with.

First etchings off my own press

Having come into a modest amount of money recently, I decided to spend some of it on something I've wanted for years and years but have never had the discretionary cash to spend. It's a small intaglio press, for printing etchings, dry-points, mezzotints and the like.

It's made by an Italian company called RGM, and I got it via Amazon. It's very small compared with the presses I used at polytech, but it works well enough for my purposes. The bed is 270mm wide by about 450mm long, so realistically I couldn't print anything much bigger than A4, but that's no great problem as all my intaglio work to date has been quite small. The bed is just a piece of 3mm steel, so getting a longer one if need be wouldn't be any problem, though I'd need a new felt to fit, and that would probably cost a lot more than the steel.

What I am going to have to do in pretty short order is organise a dedicated workspace for it. It really needs to be clamped down to the workbench, as there's not enough weight in the press itself to keep it from moving around under the back-pressure of the crank.

Here's my first trials, using a couple of old plates, and printed on some offcuts of 360gsm Fabriano I nabbed out of the waste-paper bin at school.

I'm pretty happy with them, and with the press.

More Etching

I imported some Lascaux acrylic etching resists to replace the rather more toxic and troublesome resists I've used up to this point. The first ones I tried out were the stop-out and plate-backing resists, which I used to make this little 50mm plaque.

It's hardly a masterpiece, but it did demonstrate some of what I needed to know about these new materials:

• They go on to the metal very well, and they seem to be highly acid-resistant.
• They don't like a very highly-polished plate, but they adhered fine to this one which I polished with 0000 steel wool. I guess that will mean that if I don't want any plate tone in my prints, the plate might need a bit of localized polishing after etching is complete.
• They cure pretty quickly, as acrylics tend to do.
• It's not a good idea to try to accelerate drying with heat, as the differential in thermal expansion/contraction between the resist and the copper can dislodge small areas.
• You'll need to be washing out your brush very regularly or the resist will cake in it.
• It washes off the plate very easily with methylated spirits — Lascaux do offer a "remover", but meths is cheap and easily accessible. I haven't tried washing it off after being left on the plate for any extended length of time though.

The resists aren't all that cheap, but they're not desperately expensive either, and they do go quite a long way.

Next I shall have to try drawing into the hard ground with an etching needle for an intaglio line. That will be the real test.

Etching Test

I tried out etching some copper using the hydrochloric acid I could get from Bunnings. It was kind of successful, but only kind of.

The acid I can buy over the counter is pretty puny stuff; it's only about 28%. I can boost its activity somewhat by adding hydrogen peroxide, but again the stuff I can buy easily is only 6%, so the added oxidizer is offset quite considerably by the fact that I'm diluting the acid with mostly water — I'd prefer using at least a 30% peroxide solution.

What that means is that etching takes a long, long time, and the shellac I was using as a resist just isn't up to the task; it started to break down after an hour or so. If you zoom in on the image, you'll be able to see where the acid crept in under the seams where two layers of shellac met.

I'll see if I can lay my hands on some proper resist lacquer, which should do a better job. I'd like to get some stronger acid too, but that's likely to be problematic.