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Etching

Tue, 09/09/2008 - 20:15 — dwolpoff

David has been working on a new home project...
"Galvanic Etching"
Moose

I won't attempt to dissect exactly what Galvanic Etching is, or how it works, as the topic is variously covered and discussed online. However, I will attempt to document what I've done, how I did it, and then just get down to the dirt of showing you a bunch of pictures.

I will caveat this discussion with two facts:
1. I am not a role-model. I am an engineer and experimenter.
2. Playing with electrons can be dangerous. Please be careful.

In very brief, a piece of metal is masked with a pattern or image, submerged in an appropriately conducting fluid. Current is passed through the piece, through the fluid and a return electrode, and through the chemical processes induced, the material is etched away.
To put it even more briefly, current turns a sheet of brass into this:
Sai begins

The process has to steps: 1. preparing a piece. 2. etching with the rig.
In step 1, we clean a piece of brass sheet. We clean the piece with soap and water and a Brillo-pad sponge. We rinse, and leave it alone. If you get fingerprints on here, you'll etch those prints into your final part.
Cleaning
More cleaning

Simultaneously, we'll take a printout of a piece of artwork, and the artwork is copied onto a piece of press-n-peel blue, which is a masking material intended for acid etching of circuits. The type of ink is pretty critical, and press-n-peel's manufacturer does a good job explaining the nuances. Suffice to say, we print out our image, and use a photocopier to copy onto the blue material. Note, that the images are mirrored so that they appear correctly on the metal.
Images to be masked during etching
Images to be masked during etching

We take the blue and align it carefully with our cleaned metal sheet...
Aligning the mask
Alignment is ready to go

...and then we iron the blue in place. The metal DOES get VERY hot, so once the mask is stuck in place, don't touch the piece. After heating, we quench the piece in cool water and dry it.
Ironing the mask in place
Ironed and ready to quench.
The image is blurry is the piece is tossed into cool water using pliers.

Once the piece is cool, we peel off the blue, and carefully clean any excess. You can see in the images here that the ironing near the prince wasn't perfect. Oh well. Imperfection gives character.

The press-n-peel is peeled away, leaving the mask
The press-n-peel is peeled away, leaving the mask

Now we have a prepped piece, ready to go in the rig.

The etching rig is a 500 Watt ATX power supply, controlled with one of our ATX PSU boards.
The heart of the etching rig is an ATX PSU and an ATX Breakout (PSUATX01)
The heart of the etching rig is an ATX PSU and an ATX Breakout (PSUATX01)

The power supply has its 12V rail (yellow wires) hacked off and connected via high-power cable to a set of electrodes. The electrodes in turn dunk into the tank of solution. Here's my original setup, in the bathtub for easy cleanup.
The complete overview of the rig.

During etching, current flows between the electrodes, through the solution. The current will be at least mostly proportional to the distance between the electrodes, so originally a large tank was used. The solution is experimental, but we've used the old "rootkill-n-water" as well as the ol' "saltwater" solutions. The blueish water is for brass. The white is for aluminum. The small tank with the built-in electro-contacts is our "final" tank for small brass etching.
The big tank is good for large pieces, but generally just wastes space.
The tank used for experimental etching of aluminum. Worked fairly well!
The tank used most on brass pieces. Smaller and easier to use. Note the through-panel electrones.
The tank used most on brass pieces. Smaller and easier to use. Note the through-panel electrones.
The tank used most on brass pieces. Smaller and easier to use. Note the through-panel electrones.

The process runs for however long it takes to get as deep as we want the etch. Anywhere from 45 minutes to several hours.

"Finished" Pieces

The fairytale is an aluminum piece we did in a saltwater tank. We used progressively finer sandpaper to polish the high surfaces. The background texture is the natural finish of the process.
A fairytale scene set in aluminum.

The Keyboard Cowboy is a deeper etch in thicker brass. The side angle gives you an idea of how it looks. We used a buffing wheel and rouge to polish this one.

A Keyboard Cowboy in brass.
A Keyboard Cowboy in brass, from the side.

The Moose is a replacement for the Dell emblem on the back of my laptop's screen.
A moosey circle.
A moosey dell.

Sai is a similar piece for my wife's laptop. Uncut version was shown above.
Sai dell.

The Lantern is a wedding gift created for some friends. The three panels were designed to fit the sides of a candle-lantern. We etched the panels after cutting them apart. After etching and cleaning, the panels were painted with a metallic paint, and the high surfaces sanded with a rough paper. The lantern was painted with the same metallic paint, and the handle was replaced with a piece of brass rod. The interior surfaces were mirrored, and some custom electronics were added along with a prism to give a beautiful visual effect. Remember those images that were peeled up earlier? Here's the finished piece.

Lantern Panel 1
Lantern Panel 2
Lantern Panel 3
Lantern Front
Lantern in the Dark
Lantern Fireball