etching

Hay Raid, You know, I was thinking about Roadmarks just about an hour ago. How it could be a good movie. Anyway, get that stuff they use for ecthing circuit boards at radio shack. It's ferric chloride. Stains fingers real good but will etch steel. Lacquer or wax the part and scratch through to make your image and then submerge, agitating once in a while, and check now and then 'till it's deep enough. Cheers, ERS

Electrochemical etching is an easy and safe process. It can be used to make a deep etch or a very thin surface mark. Beware of commercially available electro-marking equipment, though; it is ridiculously expensive. On the other hand, it is very easy and inexpensive to build your own. My electro-etcher is shop made from materials I had on hand. The process, materials, and equipment are almost trivial, but information is closely guarded within the industry.

For the resist, I've been happy with photo-sensitive stencils. I create the image on the computer, print it on the photo-resist using a LaserJet to make a contact mask, and expose the film using simple shop-made light box.

Knife maker Bob Warner's tutorials provide a good starting point:

out "Electro-Etcher" and "Stencil Exposure unit")

Additional practical information on the process can be found here:

Electrochemical etching requires an electrolyte. Last summer, I got free samples of three different electrolytes from IMG, intending to experiment with them on different steels, but I haven't got round to doing that yet. I did use the SC-50 electrolyte on O1 and it worked very well.

However, I also had good results with a homebrew electrolyte of about equal parts of potassium chloride and salt in water. This solution works even better with a bit of muriatic acid added. I was experimenting around with this before I got the commercial electrolytes from IMG, and it worked pretty well. The "recipe" came from a paper on sheet metal strain studies.

The original recipe in the paper was: potassium chloride, 80g sodium chloride, 90g nitric acid, 100ml hydrochloric acid, 100ml water, 4.5L

With no nitric acid readily available, I just winged it with what I had on hand and it worked well enough. I had previously tried various concentrations of plain salt and water with poor results.

On stainless steels, I have heard that the commercial electrolytes are best, but I don't know from experience.

My contact at IMG was Patricia Bruno. She was very helpful. She also mentioned something about an inexpensive "knifemaker's sample pack" with five different electrolytes that they were planning to offer. Here is IMG's web page.

Snoop around their web site for some good basic information on the process and equipment in general.

The technology is solidly within reach of the average do-it-yourselfer. I made both the light box for exposing the stencils and the electro-etcher for a fraction of what the commercial units cost, all from information available on the web. My total out-of-pocket equipment cost was about $8 for the high-output fluorescent light bulb in the stencil exposure unit. Everything else was already on hand in various junk boxes.

I did buy photo-sensitive stencil material and developer. The stencil material was $12 for one 8.5 x 11 sheet, but since the marks are small and a stencil can be re-used for some time, one sheet goes a long way. The developer is a concentrate and a quart cost me $20. I have no idea what's in it -- for all I know it could be plain water (G).

Before I got the stencil material from IMG, I used a different photo- sensitive material, called PhotoEZ High Resolution. As far as I know, Gwen Gibson Designs is the only source for it.

Five sheets were $38. This stuff works a little differently. It doesn't require a special developer (just water) and it can be exposed in sunlight. I don't think the screen is as fine as the IMG stencil material. It doesn't handle fine detail as well. Also, the emulsion appears to soak up some electrolyte in use, which can cause blotches to appear on the mark. If you're doing deep etching and don't need fine lines, though, this stuff does work. You just have to rub off any blotches with an abrasive pad.

By the way, I tried using ferric chloride and was disappointed in the results. It's messy, takes a long time, tends to undercut, and presents a disposal problem.

Good luck!

Jim

Damn! Seems I never proofread well enough. The above is incorrect. The image is printed on ordinary paper, to make a contact mask for the resist. Sorry for the confusion.

Jim