Electrochemical Etching

This post documents another attempt to mark my reels. Here I have used an electrochemical etch kit from Lectroetch. They promote its use to knifemakers, where the blades are typically steel.
IMG_3971
The kit consists of a low voltage AC transformer with pad and alligator clip electrodes, bottles of etching electrolyte and neutralizer, and some stencil material.

The stencil material is a laminate of permeable and impermeable layers. The impermeable layer can be rubbed away with a stylus. It can also be removed using a mechanical typewriter (remember those?). Below are stencils that Lectroetch made for me.
IMG_3972

This is my fixture. I am etching the oversize head of a nickel silver screw, which threads into the center hole. A small groove at one corner is a grip point for the alligator clip.
IMG_3973

Here I am ready to etch. The stencil is secured in position over the screw head.
IMG_3974

After etching with the wetted electrode pad, I had a black image. But when I wiped it with the neutralizer, most of the black oxide came away.
IMG_3975
I sent a nickel silver sample to Lectroetch, and they confirmed that the oxide does not adhere on this material. So it looks as if I can get an untinted etch, if I can figure out a way to remove the rest of the oxide without defacing the image.

I later tried etching some 303 stainless, and the black oxide adhered.

One problem with the etch on both nickel silver and on stainless is that it is quite shallow. The logo is quickly obscured by a little sanding at 1200 grit. I think that the engraving done by a jeweler, even by diamond point drag, is more durable.

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2 Responses to Electrochemical Etching

  1. Guy Lautard says:

    Dave,

    A Cronite Engraving Machine might do the type of work you want to do. You can see some info re same on my website, or message me. Best, Guy

  2. dave49 says:

    Readers,
    A Cronite machine does the function of a pantograph, but with a different mechanism. This is a relevant response to my post on electrochemical etching because the process involved here is chemical etching (ferric chloride). I had some further private Emails with Guy and will quote him because all this was a revelation to me:

    “The Cronite engraver does not use a pantograph mechanism. Instead, it uses a gimbal mechanism. The higher up the column you move the gimbal part, the greater the reduction from the size of the master. Masters are easily made by the user – I could teach a dog to make masters in 10/15 minutes. The output of the machine is always smaller than the master. The Zero model can reduce to infinity. The Universal model does not go so small, but it can produce italic (sloped) lettering from straight up and down masters. Anything that can be done as a line drawing can be turned into a master – a drawing of a boat, a fish, a letter or a number from a book of fonts – anything like that – can be cut by hand into a sheet of 1/16” white styrene plastic (VERY cheap stuff to buy) or into sheet copper (more durable). After the master is first cut by hand, you give it a little rub over with steel wool, to take the little burrs off, which immediately makes it much nicer to handle.

    “Then you can use it on the Cronite engraver to scribe your design at a smaller size onto your workpiece. You put a waxy resist on the workpiece – which can be copper, aluminum, brass, steel, stainless steel, and I think even sheet zinc – and the non-rotating diamond point cuts the design down thru the wax to expose bare metal, which is very easy duty. When you have traced out all the lines on the master, you take the work off the machine, rub some spit on the area where the design is, and then put some ferric chloride (FeCl3) on the wax. The spit makes the wax wetable wherever it is put on the wax, and the FeCl3 will bead up on that area only. The hydrochloric acid in yer spit starts the etching action. The longer you leave the FeCl3 on the work, the deeper the etch will be. If the work is warmer, the etch will go faster. The speed of the etch is also dependent on the concentration of the FeCl3, and stronger does not necessarily mean faster etching. Etching time might be anywhere from 5 or 10 minutes to 2 or 3 hours. Final appearance depends on certain details that may or may not be incorporated into the masters, how long the etching goes on for, and how deep it goes.”

    I posed further questions on the gimbal mechanism, and he offered this link as explanation:
    http://www.circuitousroot.com/artifice/letters/pantocut/eaton/index.html#epmco-1911
    My explanation of the Cronite machine is that it is a rod hung by a gimbal joint. The longer portion of the rod, suspended below the gimbal, is the tracer for the large pattern. The shorter section of the rod is above the gimbal and pushes around a table that carries your work piece. The table is supported by balls so it moves easily in X and Y directions. The scriber is fastened to the machine frame.

    The revelation for me was the use of the wax resist and spit. Whether you have a Cronite, a pantograph, or a CNC engraver, this technique is applicable.

    By 2015-2016 I am making reels with bronze frame. The electrochemical etching that failed with nickel silver may be workable with bronze. I have not gone back and tried, since I have made a CNC engraver with a high speed rotary spindle.

    Guy’s web site is most interesting, http://www.lautard.com

    Dave

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