Electrolytic Machining of Brass - Part II:
Jake von Slatt — Tue, 01/16/2007 - 06:37
After the perhaps overly optimistic attempt at electrolytic machining in Part I, I decided to try etching parts from thinner sheets of brass. Sheet with thicknesses of .010 and .015" were chosen and I used the advanced image search feature of Google to search for black and white appropriately steampunk images.
Once I had collected a few that I liked I arranged them in OpenOffice.org Draw and scaled the sheet to a convenient size. After saving the file I printed out a copy and used a Sharpie to fill in the blank areas. This was much easier and quicker then attempting to do the same operation on the computer. Once I had the blank areas filled, I scanned the image back into the computer, composed a pair of mirror image masks, and printed the result on some Press-n-Peel Blue.

I've discovered that our new Samsung CLP-300 color laser printer lays down an excellent layer of black toner on the Press-n-Peel. Unfortunately, it will not feed the Press-n-Peel film through by itself, it jams almost instantly. However, it you fold a piece of paper over the leading edge as shown, it feeds through the printer with no problem at all.
I polished the brass highly prior to ironing on the film as I have discovered that this minimizes the amount of finish work that the brass requires after the etch.

One of the trickiest tasks was to get both sides of the film justified before ironing it on to the brass plate. I lined up the two haves carefully on a light table and then taped them to a folded piece of paper to form a book.

As you can see I'm still trying to get the ironing-on process down, the opposite side of the brass from the iron was particularly hard to get a clean mask. I cleaned up the lines and filled the voids with a small paint brush and some paint.


Here are the results - this is after about 45 minutes in a 120 degree Fahrenheit bath with a single car battery. The etch goes clear through most of the design. The top is etched slightly more then the bottom of the plate, Perhaps this is due to the hot electrolyte rising or the cathodes may be slightly farther from the workpiece at the bottom.

Below is a .010" piece of brass that was etched with two car batteries in series in about ten minutes - it was left a bit too long. A note of caution, when the plate fell apart it shorted the batteries. There was smoke, if I had not been monitoring things closely there might have been fire.

Here's a close up of one of the "charms". You can see that the two masks on either side were not quite aligned. Some pieces were better, some worse.


Here is the complete collection including Sherlockian, cog, and Ankh earrings. The other charms will, along with a length of chain, form a necklace.
The teeth on the cog earring are actually quite small and detailed. This will be quite a successfully technique once I figure out how to align the two masks with a high degree of precision and once I determine the best way to iron on the toner mask. One idea that I have read about is to remove the toner fuser from a laser printer and use it instead of the iron to melt the toner to the brass plate.
Please note that several aspects of this article include dangerous compounds and energies. Copper sulfate is poisonous and the used solution needs to be disposed of in an environmentally sound manner. Car batteries can also be particularly dangerous, accidentally shorting the poles can lead to fire, explosion, and flying hot acid - very bad, that. This article makes no attempt to comprehensively address these risks. The responsibility for your safety and the safety of those around you - should you decide to attempt similar experiments - is your own.
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Awesome stuff!
Tim_D — Thu, 01/14/2010 - 22:22I wish this site had been around or I had thought to look for the information back when I was doing a fair amount of etching! I never thought to add electricity to the process, and I just used ferric chloride from Radio Shack. The ferric chloride works well, but it is molasses in January slow!
I found laser transparency film to be a reasonable substiute for PnP - much easier to find and less expensive. I never tried double-sided etching with it though. One advantage of the ferric chloride's slowness, however, is the ability to remove the part from the etch tank, rinse it and apply a new layer of "resist", usually in the form of black Sharpie. That process allowed me to etch something in relief, then stop the etching and coat the previously etched area before putting it back into the tank to etch all the way through.
Great site and awesome technical information!
Tim D.
Way cool method
RoccoDNYC — Thu, 10/01/2009 - 22:40I like your method for etching since in includes chemicals, electricity, and danger. Have you tried a simple muriatic acid bath? Use a poly spray and a stencil. With the thickness of brass your using you could stencil one side. The muriatic acid won't eat through the poly spray. One note of caution is that the fumes from this method are way nasty. Either use a ventilation chamber or do this outside. I use this method to make custom gobos from steel. I use a plastic plate to hold the acid. Hardware stores sell muriatic acid to clean concrete. I will also say to always wear latex gloves and safety goggles when doing this. Keep a big bucket of water handy for accidents to neutralize the acid. When the metal is done being etched drop it into the big bucket of water to stop the acid from eating any more. I have done very intricate detailed patterns with this method. I usually draw the pattern on the metal first, but that's because I like to free hand my designs. Then I spray the poly on. Then I trace my line drawing with an exacto blade. I don't use much pressure since the poly is super thin. I like the idea of using a stencil. That way mass production could be done. I suppose that overhead projector transparencies cut into the shapes wanted could be ironed on to achieve the same result. Let me know if you have thought of this and see any downsides to using this method with brass. I know muriatic acid will eat brass, but since I have only done this with steel I don't know how well it works with brass.
Register marks to line everything up nicely
curiouschilde — Mon, 01/19/2009 - 11:55So it's been a while since you originally posted this, but i just came across it. I hope that you have had good success with lining things up. I have a suggestion for you to help matters.
Above, someone mentioned putting plus marks. Well that's a good start. If you place registration marks in the corners(larger plus marks). This should be done on the printed sheet, so that it transfers along with everything else. Transfer one side to the brass. Then, in the intersection of the registration marks, you drill a small hole. By doing that, you can match up the intersection on the other side with the drilled hole.
I hope that makes sense. If not, let me know.
Cheers,
AJ
Chemical etching brass
wizodd — Sat, 12/27/2008 - 21:59Two things.
1) you should have a fuse in the circuit to avoid blowing up your battery--you were very lucky.
2) you are allowing too much current too fast to do a clean etch job, put a current-limiting device (like alight bulb) in the circuit. Using a cold etchant bath will also help, as will periodic or continuous mixing of the electrolyte.
A slower etch should give a cleaner edge. Also, with metal this thin, etching from once side only might be easier, pattern once side and coat the other side with resist.
For quantity production, etch your design into a steel tool and us a press to punch them out.
There is a jewelry book about production desgin, tooling and machining printed in England a couple decades back (I looked, but could find neither my copy nor a reference on the web--the title was something along the lines of "tooling and production for the small shop.""
Dies can be etched in steel with ferric chloride and thin metal sheet can be punched using the die, a punch and a modified auto jack. It is possible to produce many copies before the die/punch needs to be replaced (and even then, you can use the old ones for thicker sheet.)
Such a system avoids the problem of chemical waste and the hazards of acids, H2 and electricity!
Please, please, please do your research before setting up anything like this chemical etching system--there's no excuse if you have Net access for not building a safe and effective piece of equipment--this stuff is not new!
suggestions for lining up
MockingBirdtheWizard — Wed, 08/13/2008 - 21:58I'm about to start playing with electroplating this weekend, so am doing a bit of reading up on this stuff.
as a suggestion for linig up the prints, if you print a PLUS sign at the corners of the page, it can help be a measure to make sure eerything is right (when placed onto a light table)
for lining up on the plate, from either side, I would also include a print of a long line along the side of the print.
then, I would use a paper cutter (one of those special tables) to cut along that printed line.
this will give you a true edge to line up against the side of the metal plate, so everything should line up well.
ah, slight modifitcation, a line along the side, and bottom, which would allow alignment to the bottom left corner of the palte, or some such.
does that make sense? or is that only in my head....
hmm.. another way of saying the same thing: print fake corners on the page, use those to lign up to the metal plate.
:-) geez, I hope there's no exploding acid this weekend... ech..
Registering two-sided masks for etching
WmRMeyers — Sun, 08/10/2008 - 20:25Jake, try using the method animators use to get their animation cels lined up properly.
See http://www.sci.fi/~animato/index.html and scroll down the menu on the left to "pegs, disk, and desk. Check out the info there, and I think you'll have better success at getting things lined up properly.
This is a Finnish animator's DIY site, in English. I've had it stored on my computer for years, as my son is interested in animation, and checked it out again today to make sure it still works.
Bill