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hedgehog1
03-31-2013, 05:59 PM
Salt Water Etching - hedgehog1's journey.

Etching of aluminum saber parts and shrouds is a wonderful way of adding detail and interest to any saber. Metal etching to produce art has a long and honorable history. Perhaps the best know art form using this technique is the intaglio printing process where an artist etches an image into copper plates. These plates are then used to print short runs of the artwork.

Etching has also been used for years to add detail to fine jewelry and high quality knifes. In modern manufacturing methods, circuit boards are etched in large batches every day.

Acid based etching is the most common method seen today, but this present a problem for me. I have the honor of being allergic to a great many things: most animals, pollen and many chemicals. The reason I use the 'hedgehog1' name is that because of these allergies, I have only had very small animals for pets such as Hamsters and African Pygmy Hedgehogs; so hamsters and hedgehogs are always a happy thought for me.

I have used acid to etch circuit boards in the past. I was able to survive it by lots of coverings and masks. But even then I was faced with another issue: responsible disposal of the used acid.

These issues made the idea of Salt Water Etching very appealing to me. I am not allergic to salt (Yay!) and the solution can be stored between uses without worry of pets or kids getting poisoned by the stored solution. Disposal can also be done in a safe and environmentally appropriate way as well.

My primary two influences in the design of my Salt Water Etching system are from these two links:


Madmaxx presents his Opus (http://forums.thecustomsabershop.com/showthread.php?14801-Madmaxx-presents-his-Opus)

INEXPENSIVE ETCHING OF INTAGLIO PLATES IN SALT WATER (http://www.cspoguegraphics.com/electrolysis.php)

In may ways, these two links are really very different. The intaglio link shows just the final 'correct' (for them) way they found. Madmaxx give an honest play-by-play of what worked and did not work for him. I actually learned a great deal from both presentations (and discovered just how determined Madmaxx is once he starts a project).

My first design decision was the etching tank. I wanted a tall and narrow tank with a seal-able top to store the salt solution between Etching sessions - something like a Star Wars Bacta tank, but rectangular to have four corners to place the cathodes into (Note: Anoids are positive, Cathodes are Negative). On Amazon (my second favorite store after TCSS) I found this clear container:

http://imageshack.us/a/img803/8571/saltwateretch10.jpg

It needed a stable base for the work it is to do, so I attached a circle of acrylic from Tap Plastics (a local Plastic/Acrylic/Fiberglass supply store) to the bottom of the container:

http://imageshack.us/a/img543/9069/saltwateretch15.jpg http://imageshack.us/a/img109/3386/saltwateretch20.jpg

This was attached using Automotive Urethane Windshield Adhesive that advertised its ability to 'flow'. The more liquid like behavior made it easy to attach to two pieces together. The product I selected was also odorless (not required, but I preferred it).

The next piece I built is intended to center the part being etched to avoid contact with the cathodes:

http://imageshack.us/a/img705/5250/saltwateretch25.jpg

I will be honest and say that I don't know if this will really help or not. I will have to use it a few times and see if it gets in the way to much. It was assembled using a smaller acrylic circle and an 18 inch length of 3/4 inch acrylic tube. I did have fun drilling holes in these parts using a special drill bit for this plastic. They were attached to each other using standard acrylic cement.

The assembly of the cathode array took several attempts before I got something I liked. The cathodes are 3/8 inch aluminum rods with a small hole in each one to attached the negative voltage too:

http://imageshack.us/a/img826/7469/saltwateretch30.jpg http://imageshack.us/a/img198/9341/saltwateretch35.jpg

The rods are held together using wire ties (cut to length) and heat shrink. I am amazed at the many uses I keep finding for heat shrink. It is not Duct-Tape great, but it has it place(s) in my world.

Here is the whole tank assembled:

http://imageshack.us/a/img838/69/saltwateretch40.jpg

Two keys to a successful salt water etch are the recipe for the solution, and the nature of the electric power used. I will get to the solution in the next post, but for the power I used the same power supply as the intaglio folks did:

http://imageshack.us/a/img836/1667/saltwateretch45.jpg
Link to RS-100-3.3 (http://www.trcelectronics.com/Meanwell/rs-100-3.3.shtml)

It is a 3.3 volt, 20 amp power supply. It has a trim adjustment pot, which allowed me to turn the voltage down to 3.012 volts. Voltage and current caused issues for Madmaxx in his etching thread. While the voltage from 2 'D' cell batteries was correct (3 volts), they just didn't have the current to get the job done before he died of old age. When he went to using a car battery charger, he had the current, but the voltage was too high and the process was slowed (but better than with the 'D' cells). The intaglio folks faced similar issues with the massive size that printing plates can be. In the end, they found voltages from 2-3 volts worked best and did not cause secondary etching issues. The 20 amp supply gave them etching process times about the same as acid etch processing times.

So, this all had to go into a box with a power switch, adequate heat dissipation and basic electrical safety taken into account. The box I used was picked up at my local Radio Shack a few days ago. I think it is the ugliest box I have ever seen. It looks like a left over from the 1950's. I just had to have it:

http://imageshack.us/a/img801/6180/saltwateretch50.jpg

I plan to add lettering that reads: 'ACME ETCH-O-MATIC' on it; I think this will really complete the 'hideous/mad scientist' look.

The box contains an on/off switch, a ruby-red 'power indicator' light that uses a 120 volt neon bulb (another hideous 1950's left over, also bought at Radio Shack), a 20 amp fuse holder protecting the 3 volt output and two banana plug jacks for the three volt etching output.

I mounted the power supply with both the metal screen sides exposed to allow for the best possible passive cooling:

http://imageshack.us/a/img15/3681/saltwateretch55.jpg

And here we have the final product (minus the tacky 'ETCH-O-MATIC' lettering to be added later):

http://imageshack.us/a/img829/2521/saltwateretch60.jpg

hedgehog1
03-31-2013, 06:02 PM
The 15% solution.

The other import part of effective salt water etching is to use the correct salt and water.

Common table salt has additives that allow it to pour when the humidity is high. Tap water has various minerals and additives. These extra trace additives can interfer with the etching process, and also cause secondary etching issues.

Ideally you should be using as pure a salt as you can find so that it is nearly pure sodium chloride. Kosher salt is a great choice, and it is readily available in most grocery stores (I found it next to the matzo balls at my market in the 'ethnic' isle).

http://imageshack.us/a/img594/9048/saltwateretch05.jpg

The other component is the water: Use distilled water rather than tap. Distilled water is pure H20, so pure it is unhealthy to drink because it has no minerals in it!

The mix ratio is 15% Kosher salt, 85% distilled water.

hedgehog1
03-31-2013, 06:03 PM
Place holder reply for my etching runs with times and results. To be populated over the next week or so.

madmaxx
03-31-2013, 09:09 PM
Sweet holy crap Hedgehog that is a very cool looking rig for the etching buddy!...I'd go with Frankenetch as a name though.well done and DONT inhale the fumes dude they really arent good for you

hedgehog1
03-31-2013, 10:13 PM
Sweet holy crap Hedgehog that is a very cool looking rig for the etching buddy!...I'd go with Frankenetch as a name though.well done and DONT inhale the fumes dude they really arent good for you

Well, if it is worth doing, it is worth over doing. Actually, My goal is to make etching a quick process so I can use it often. I have to think on the Frankenetch name. I was going with the coyote/road-runner theme, but Frankenetch has a certain appeal. If I add a lighting rod to the roof....

TrypWyr
03-31-2013, 10:27 PM
I'll admit, you had me hopping on Amazon to see how much this little adventure would cost me... :)

I've been kicking around the idea of some etching myself, but so far it's only for one build. I can't wait to see the rest of this patented Acme craziness to help me make a decision!

hedgehog1
03-31-2013, 10:34 PM
ACME Products are recommended by road-runner chasing coyotes worldwide!

Knighthammer
04-01-2013, 08:53 AM
WOW - now this is an etching rig!