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Author Topic: Brass etching - FAIL  (Read 50238 times)
Gozdom
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« on: August 22, 2009, 10:05:49 pm »

Hello there. I have thoroughly read several guides on electric etching of brass and copper, and still have only achieved little result. I have no idea what is wrong.

First tried salt + distilled water, and small clock parts. Resist was either nail polish, enamel or OHP marker - there was no problem with that. The circuit has a bulb in it, so its not broken. Current source was an adjustable adapter (1,5-12 V), also tried a car battery charger (6A).

I managed to oxidise the exposed surface to a dark brown. Wiping off the resist revealed a shiny brass pattern. Howewer, the depth was only about 0,1 mm or less. Even the finest sanding almost erased everything. By removing the oxide, the ornament could hardly be seen.

This result was achieved in a few minutes, however, having it in the bath for an hour or more did nothing else. The cathode was bubbling neatly.

So I bought copper sulfate (98% purity). I tried a light solution, then even an oversaturated one (with crystals sitting at the bottom). The result is the same. Lightly etched, almost untouched except for oxide. I even tried to add table salt and vinegar later, in despair, to no avail.

The work piece was cut from a brass ribbon used for doorstops. Seems brass for me. I have sanded thoroughly and degreased with ethanol. The solution was in a coffee cup, about 1,5 dl. What is wrong?
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JingleJoe
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« Reply #1 on: August 22, 2009, 11:28:43 pm »

I think you have your polarity connected incorrectly.

Make sure your set-up is correct, the same as this diagram


Don't use too much salt/stuff either, there is a tipping point where it starts to work less well the more you add.
Instead of a bulb I think you could also use a resistor in order to let more electricity flow, not sure of what value though. Try some higher ones like 100k, 50k, 20k and if you can get to a suitably low one that makes the etching work better and things aren't getting too hot/blowing up then you will have found the right resistor!
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Gozdom
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« Reply #2 on: August 22, 2009, 11:48:20 pm »

No, polarity is correct. Checked it 100 times. Intriguingly, the piece of brass on the negative pole has a nice copper plating built up. But the reverse has not happened on the work piece.
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JingleJoe
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« Reply #3 on: August 23, 2009, 12:03:31 am »

Are your crocodile clips getting in the fluid?
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Gozdom
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« Reply #4 on: August 23, 2009, 12:51:17 am »

No clips. I use copper speaker wires, hooked into a hole in the workpiece and the cathode. They were submerged though, yes (part of them insulated). Could this be the problem? Should I use  strips of brass?
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jringling
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« Reply #5 on: August 23, 2009, 01:51:51 am »

longer etch time or more amps...
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JingleJoe
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« Reply #6 on: August 23, 2009, 01:54:17 am »

If the wire was only connected by a hook then that might not be enough, you need a good strong connection, but there is something else wrong here because I think you could have been etching rather well by now. I have no idea wht you can try but that.
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Satanic Mechanic
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« Reply #7 on: August 23, 2009, 05:56:49 am »

I too use this process to clean rust off of engine parts.  Is the chunk of metal you are using for the cathode galvanized?

SM
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Gozdom
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« Reply #8 on: August 23, 2009, 10:52:10 am »

It shouldn't be. It's from the same brass ribbon used for doorsteps, sanded. But I'm beginning to doubt if it's brass. However, I also tried clock parts with the same result. Last night I had it in the bath for hours. It should have dissolved, but its untouched.
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Gozdom
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« Reply #9 on: August 24, 2009, 02:36:53 am »

I might have got a clue. I used about 1 dl of the solution, these are very small pieces I am etching. Could it be the problem? Could a 4x3 cm piece of brass saturate the liquid and cause the etching to stop? Perhaps a larger volume would provide a deeper etch? I'll try tomorow.
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elShoggotho
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« Reply #10 on: August 24, 2009, 08:53:15 am »

Sounds like you're not etching into the brass, but copperplating the other piece with your wire. Remember: Do NOT hang the wires into the solution!
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Gozdom
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« Reply #11 on: August 24, 2009, 10:41:28 am »

I see. What's causing this? After all, the wire is just another piece of metal.
Also, shouldn't the wire have dissolved by now, sitting in the soultion for hours under current?

I'll try a brass strip as a handle.
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jringling
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« Reply #12 on: August 24, 2009, 10:54:59 am »

I do not use a lightbulb or any other load in the circut. try everything the way you have it, but take the bulb out....
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elShoggotho
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« Reply #13 on: August 24, 2009, 11:06:30 am »

I see. What's causing this? After all, the wire is just another piece of metal.
Also, shouldn't the wire have dissolved by now, sitting in the soultion for hours under current?

I'll try a brass strip as a handle.
You want the current to flow through the brass. Since the way of least resistance is through the copper, you should keep the copper out of the solution. Only the part that you want to etch and the electrode should be immersed. I repeat: If you put the copper wire in, it will disrupt the etching process, because you'd etch the piece of least resistance.
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jringling
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« Reply #14 on: August 24, 2009, 12:45:00 pm »

I etch both copper and brass in my tank. My anode is a 3"X5" sheet of brass suspended by brass ribbon. This now has a heavy coating of copper. The cathode is suspended either by a piece of brass ribbon or copper wire (whichever is easier for the piece). I have never noticed a difference in etching no matter what the cathode or hanger is...

I use a tank that holds about 2l of saturated copper sulfate, a 12v car battery, and a car battery charger. The battery is actually dead but I keep it in line to act as a buffer. I run the charger at both 6 amp and 2 amp, depending on the size of the piece and how big of a hurry I am in. I place the anode and cathode as close together as possible, sometimes only 1/4" apart, and the etching takes 30-60 minutes. I admit my etches are not the cleanest, but I blame my masking technique and my lack of patience.

I still think the problem the OP is having is low amps making it to the piece being etched.
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jringling
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« Reply #15 on: August 24, 2009, 12:48:59 pm »

Another set-up I have used is a saltwater soaked piece of craft felt between a cathode plate and the etching piece, powered by a D cell battery, with no light or motor in the circut, The felt gets very hot a boils off the saltwater, so this must be watched closely and the felt resoaked when needed....
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Gozdom
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« Reply #16 on: August 24, 2009, 01:34:07 pm »

I'd be afraid of running it without a bulb, that would mean shorting the adapter and possibly ruining it. I understand the copper wire problem, so I'm trying with brass hangers, but in a saltwater solution, to save precious copper sulphate until these problems are sorted out. Thanks for all the help!
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Gozdom
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« Reply #17 on: August 24, 2009, 06:20:18 pm »

It was an amperage problem. I still don't want to short the adapter or the charger, so I took a small 12V battery (used in alarm systems), and with it, the etch finally bit deep. Topic solved, thanks all.
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jringling
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« Reply #18 on: August 24, 2009, 06:39:15 pm »

Glad to hear your set-up is working... now you must post photos  of the result...
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punkandska66
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« Reply #19 on: August 25, 2009, 03:41:01 am »

Woah, this is so cool. I tried this and it worked for me. I never though I could do something like this! I had an altoids tin and since the ingredients were etched in, I etched the whole tin down to the level of the part that was already etched. If that makes any sense... I tried to paint a pattern on and etch that, but the paint peeled off really fast. I'm wondering how to do a picture, can anyone help me? I've made shirts before, and I'm assuming you start by making your picture into a B&W high contrast picture, right? Past that, I've got no clue...
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JingleJoe
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« Reply #20 on: August 25, 2009, 04:01:03 am »

If you want to transfer an image from your computer you need some specific things, google "press n peel blue" for the best way.
However you can also put duct tape on your tin then cut simple designs into that Smiley
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punkandska66
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« Reply #21 on: August 25, 2009, 04:01:59 am »

Tried the tape thing, but turned out terrible. But thanks for the help! I'm going to look up that Press 'n' Peel stuff. Actually, now that you mention it, I think I saw a video on Make that had Jake Von Slatt in it, and he was using that stuff for his etching.
« Last Edit: August 28, 2009, 07:21:23 pm by punkandska66 » Logged
Professor Damien Tremens
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« Reply #22 on: August 28, 2009, 02:40:45 am »

I always use an aquarium bubble bar below the etching plates, to make sure that you get maximum circulation of the
(in my case) saltwater bath. This helps to prevent a jaggy or pixelated look in the areas of the  etch with fine detail
caused by gas bubbles that form on the surface that would stay in place, and thus prevent etching from occurring in the
spots where the bubbles are. I also tend to remove the plate being etched every 5-10 minutes to lightly brush and
rinse off the residue buildup.

Using the laser printer toner transfer method, I've been able to reliably get masking transfers with an accuracy of at
least 1/64 of an inch, and closer to 1/100 of an inch on many occasions. Now if I could just remember to always have
the text reversed (mirrored) before I print out the master transfer designs...
« Last Edit: August 28, 2009, 02:48:26 am by Professor Damien Tremens » Logged

jringling
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« Reply #23 on: August 28, 2009, 07:11:04 pm »

I always use an aquarium bubble bar below the etching plates, to make sure that you get maximum circulation of the
(in my case) saltwater bath. This helps to prevent a jaggy or pixelated look in the areas of the  etch with fine detail
caused by gas bubbles that form on the surface that would stay in place, and thus prevent etching from occurring in the
spots where the bubbles are. I also tend to remove the plate being etched every 5-10 minutes to lightly brush and
rinse off the residue buildup.
I shall have to investigate the bubbler idea. I have spent huge amounts of time cleaning pictures in high-res and printed/copied multiple times to prevent the etched image from having a pixelated look. I have had bad luck when rinsing a plate in progress, often lifting some of the toner mask off of the plate before the etch is deep enough...
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sidecar_jon
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« Reply #24 on: August 28, 2009, 08:32:21 pm »

I always use an aquarium bubble bar below the etching plates, to make sure that you get maximum circulation of the
(in my case) saltwater bath. This helps to prevent a jaggy or pixelated look in the areas of the  etch with fine detail
caused by gas bubbles that form on the surface that would stay in place, and thus prevent etching from occurring in the
spots where the bubbles are.

In traditional acid etching a feather is used to waft off the bubbles...
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