I know nothing about etching, and even less about electronics, and I need some help with etching copper plate. More specifically, I need help understanding resists and mordants and how best to use them to get the effect that I want.
I have a 3" diameter disk of solid copper that is 3/16" thick. I want to etch an image into both sides of the disk. I created the images on my computer. They're high-contrast black and white images without shading.
This is the URL to a photo of the disk:
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I ordered these materials:
Etching tank w/ air pump and heater
Ferric chloride solution
Hydrochloric acid
Citric acid powder
Press-n-Peel Blue
Z*Acryl Stop Out Resist
Z*Acryl Ground Emulsion
I plan to print the images onto the PnP Blue with a laser printer or photocopier, and then iron them onto the copper disk, which then goes into the etching tank.
Questions:
Will the extra mass of the thick copper disk retain too much heat for the PnP Blue to stick correctly?
Are there any other methods of getting a resist onto the copper that I should consider?
Can I use the Z*Acryl to protect the edges of the disk from the etch?
I want the image etched deep into the copper. Which mordant should I use to get the bestest/fastest results? Ferric chloride, Ferric chloride + citric acid powder (Edinburgh Etch), hydrochloric acid + peroxide, or..?
Am I insane? Does this have any chance of working?
Possible. If so then you could heat up the whole copper disk with a hot air gun or some other method. I don't know anything about PnP Blue so I don't really know.
A resist is any material that will resist the etchant. The is really almost anything that is non-water soluble(so it doesn't come off when etching) and won't react to the etchant. So for the ferric chloride it would be just about anything that isn't metal. It will need to make a very good bond with the copper though so that etchant can't lift it up.
Probably. Try it and see.
I don't know which is better. You can try different ones and see. I haven't done anything like this so I don't know which is best.
BTW, The ferric chloride, etc are etchants and not mordants.
I'm sure it will work but you might have to do some experimenting.
Since you already ordered the stuff you might as well experiment. I think your going to have a hard time etching the copper if its that thick and you expect any depth.
The problem that your going to have is that the deeper you want to etch the more it will interfer with your artworks borders.
The etchant doesn't just etch straight down but also into the copper from the sides.
i.e.
====_____====
--------------
Suppose the === represents some type of resist while ____ is plane copper.
When it etches you'll actually get soemthing almost like
==== ==== \\ / \\ /
---------------
(need to view in fixed width)
For very thin copper cladding this isn't a real issue but for something as deep as you want it could be a real problem.
You'll definitely be able to etch it though. You'll need some way to have it etch evenly as you could have a problem where it etches more in some places than others.
I would imagine you might want to use a more dillute solution of etchant and have it work over long periods of time to get a more uniform etch. You'll need some type of agitator to do this though.
My advice is just to experiment and see. Maybe etch on some pennies or something first(grind down the surface if you can). You can draw a pattern on the copper using some etch resistant non-soluble material. I think a sharpie will work fine.
If you can't find any exact answers then your going to have to play around with it and see what works best.
I just come up with an idea that might solve the problem for deep etching. You could etch a little of the pattern, take it out, fill it with water so it fills the etched out part half way or so then spray on some etch resist and then remove the water. Repeat several times.
Not sure if that makes sense(or if it will work well) but it sorta looks like
==== ==== \\ / \\ /
-----------------
-----------------
fill with water
==== ==== \\ / \\^^^^^^^^^/
----------------
-----------------
(^^^^ is water or some other liquid)
Spray etch resist or use some method to cover walls that are exposed,
Probably to much work and not sure how well it would work. (I imagine that a problem would be that spraying the etch resist would get into the water and then in the copper)
For the toner to transfer it has to be hot enough to melt. You'll have to preheat the disk (or it'll cool the toner too much), but it'll work.
The toner idea sounds pretty good to me.
I don't know that product. I've used Krylon clear acrylic very successfully when etching circuit boards. Colored acrylic would be a lot easier to see & inspect for defects. I use 2" wide plastic mailing tape to protect large surfaces from the etchant.
I don't know which is best. I use FeCl because it's easy to get. It stains skin, clothing, and sinks ferociously.
I'm with Jim Stewart--if you go super-deep undercutting will be problematic, but I suspect you'll be able to go plenty deep enough to render a nice, durable image with the setup you've proposed.
The other variant that might be easier (although you might still have to experiment to get it right) is the spray on UV sensitive photoresists (which I think require a caustic developer to dissolve the unwanted areas). Sunlight will expose them although less reproducibly than a proper lightsource. It doesn't depend on heat so you don't have any problems with the bulk copper disk thermal inertia.
Some brands of permanent OHP pen work better than they have any right to. Experiment on scrap first to get the method exactly right before committing the main piece to the etch tank.
Possibly with a bit of experimentation. Undercutting at the edges will be an issue. Constant and consistent agitation to prevent the edges suffering damage from diffusion of unspent etch from over the resist may be needed.
The only drawback I can think of is dramatic undercutting, but I don't know enough about the etching process itself to recommend a specific etchant.
If all you want to do is impress an image, there's a process called electroetching, but it only goes a few thou deep. A google search should come up with something.
If the hole goes all the way through the copper, then definitely machine it by hand. In that case you could even do it just by drilling through the copper and then cleaning up the hole with some fine files. If it's just a depression that goes halfway into the copper, I would try a router and a carbide bit. I would use an inlay kit, like this:
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I've used an inlay kit like the one in the link for doing wood inlays. Mine came with a 1/8" carbide router bit. Carbide is brittle, so you would have to be super careful using it on copper, but I think it might work if you only take off a hundredth of an inch at a time. And lower it onto the copper very gingerly when you start the cutting. Use double sided tape to hold the copper disc down on a flat work surface, with a piece of masonite or something surrounding your copper workpiece, for the router base to ride on. The masonite can be just a bit thicker than the copper piece, cut a hole out of it and set it down on the work surface so it surrounds the copper disc and provides a surface for the router base to sit on while working on the copper. Use double sided tape to hole the masonite down too, for extra stability. As shown in the web link I gave you, you will screw a collar into the router base and ride the inside edge of a template with. A trim router may or may not have the threaded hole for the collar, so you might have to use a regular router. If you don't have a router and don't want to buy one for this project, you *might* be able to do it with a dremel and a solidly constructed jig, but you'd need to be a real good mechanic to do that sort of thing and have it work. Everybody sort of got onto the etching thing because they're electronics types and you posed the question that way, but in my opinion etching would just lead to disappointment. Etching is a surface thing. Going deep you would just end up with a pitted crater.
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