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Ferric chloride is a traditional home-use circuit board etchant. It's easy enough to come by, and the Ferric by itself is no big environmental problem. However, once you've etched a board with it, you're left with a solution with a bunch of copper chloride in it. This dissolved copper is an environmental problem, and you can't just pour it down the drain (legally) -- you're supposed to take it to a hazardous waste facility. (For instance: How to Dispose of Ferric Chloride in this FAQ. )

Wouldn't it be nice if there were an etchant that you could re-use indefinitely so that you don't have to worry about disposing of the copper, and that could be made in lifetime supply for like $10.00 with ingredients bought at hardware and drugstores? (And it's prettier too.)

I got seven words for you: Copper Chloride in Aqueous Hydrochloric Acid Solution! (Exclamation point!)

But how're you going to get CCiAHAS? Conveniently enough, by starting out with a simple two-ingredient starter etchant, and doing a bunch of etching.

Step 1: Ingredients: The Starter Etchant

For the starter etchant itself, you only need two ingredients: hydrochloric acid and hydrogen peroxide.

(OK, actually three. But the third one's copper. See the chemistry section for an explanation.)

Hydrochloric (muriatic acid, "pool acid", etc.) is available at a hardware store. The acid I got is 31.45% (or 10M) and should run around $5 per gallon. Which is more than you'll ever, ever need.

The peroxide is normal 3% for mouthwash or cleaning cuts, and can be bought at a drug store for $2-3 for a big bottle.

You'll also need a non-metallic container that fits your PCB and two standardized measuring cups.

As long as you're in the hardware store, pick up some acetone if you don't already have some. It's useful for removing the etch resist. (That's for another instructable.)

Step 2: Put the Lime in the Coconut...

Measure out two quantities of hydrogen peroxide and pour it into your non-metalic container.

Measure out one quantity of hydrochloric acid and pour it in. ("Do like you oughta, add acid to water" to minimize the chance of an out-of-control exothermic reaction.)

Be careful with the acid. This stuff (at 10 molar) is strong. Mine fumed a bit when I took the cap off. Don't breathe it directly, and be sure you've opened the kitchen window.

The starter etchant you've just made, on the other hand, is not so bad -- around 3M HCl with a medium-strong oxidizer. I find it doesn't fume much at room temperature when I'm re-using a batch.

That said, you've got to be very careful to keep it away from metal -- especially your stainless-steel kitchen sink. It'll eat the stainless coating right off. Keep plenty of water flowing at all times when you've got any of this (even a drop) near the sink.

Step 3: Add PCB and you're Etching.

Toss the PCB into the solution and it'll take off.

If this is the first time you're using this batch of solution (and I presume it is), it'll etch super-fast. This small board took only 2 minutes. Yikes!

Since I use a deep container, I tend to swirl it around as it etches. This stuff is so active, though, that I'm not sure it's necessary.

Keep the window open for ventilation because the starter solution gives off a little chlorine gas. (The end-etchant gives off much, much less.)

Also, note how the etchant gets greener over time as it eats away the copper. This is good news.

What's happening is that you're dissolving the copper from the board and turning it into cupric chloride. In the long-run, the cupric chloride will be doing most of the etching (instead of requiring disposal). For now, just watch your solution turn light green. Next time you use it, the color will deepen.

Step 4: Chemistry Break

(Note: I'm an economist, not a chemist. Please leave a comment if you've got any corrections and/or additions to this stuff!)

I stumbled on this idea when I saw this website: Etching with Air Regenerated Acid Cupric Chloride by Adam Sechelle. Cupric chloride can be re-used indefinately by topping up the acid levels and adding oxygen (bubbled in from the atmosphere). Sounds cheap and environmentally friendly to boot.

The website's got a lot of good chemistry info on cupric chloride etching. His data on etching speeds is great, and his simple titration procedure for maintaining the acidity of the solution is pretty nice.

To make the cupric chloride solution, he dissolves a bunch of copper wire in hydrochloric acid, and mentions maybe using hydrogen peroxide to speed up the oxidation, but doesn't go into detail.

Which got me thinking. You didn't have any cupric chloride yet, but you can make it by dissolving copper. Dissolving copper is the name of the etching game. So we can make one etchant that makes another etchant that's infinitely re-chargeable. Elegant.

Turns out that hydrochloric/peroxide is a common home-brew etchant (and I've re-re-invented the wheel, again) but I guess that people got so used to throwing away their "spent" etchant that they don't think about re-using it. The whole point of this instructable is that you don't throw it away, but use the dissolved copper forevermore as your long-run etchant.

Here's what's going on chemically:

Before there's much copper dissolved in the solution, Cu + 2 HCl + H2O2 -> CuCl2+ 2H2O is the dominant net reaction. That is, the extra oxygen in solution from the peroxide is oxidizing the copper metal, in presence of the acid, to make copper (II) chloride. That's our starter etchant. The resulting CuCl2 shoud be a nice emerald green color.

After you've dissolved a lot of copper into the solution, and used up all the peroxide, the copper chloride does most of the etching for you: CuCl2 + Cu -> 2 CuCl. That's the end etchant.

Eventually you etch so much that you convert all the CuCl2 into CuCl, which doesn't dissolve copper (and is a yucky brown color). As long as you've got enough acid in the solution, you can simply add more oxygen to re-oxidize the copper(I), making more copper(II) chloride and water: 2 CuCl + 2 HCl + O -> 2 CuCl2 + H2O. And then you can etch again.

Bottom Line:

Two things to maintain: CuCl2 levels and acid levels.

CuCl2: After all the peroxide is used up, and the solution starts turning brownish, you'll have to add oxygen to regenerate the solution again: toss in a few more capfuls of peroxide or bubble air through the solution or swirl it around vigorously, or just pour it into an open container and wait. It's easy to tell when you're ready to etch again, because the solution turns green.

It's also impossible to add too much oxygen by adding air, so bubble/swirl to your heart's content. If you're using peroxide to add oxygen, be sparing -- a little goes a long way, and it's mostly water so you're diluting your etchant by adding it.

Acid: Note that HCl is being consumed in the starter etchant and the regeneration reactions. So we're going to have to add a bit more acid as time goes by. If you notice that it's harder to re-green your brown etchant, it's probably time to start thinking acid.

I've tried the titration described on Adam's site a couple times, and it's pretty easy but requires an accurate scale and pure lye (back to the hardware store...). It's easier to just toss in a capful of acid every few batches of boards, which seems to do the trick for me.

Step 5: Save the etchant for next round. You're done.

Once you're done etching, pour the etchant back into your storage bottle, rinse off the board, flux, drill, populate, and solder.

Some final notes here:

1) You can make quite a bit of this stuff very easily, and since you're re-using it, there's no real reason to skimp; put plenty of etchant in your "tank." When you use too little FeCl etchant, for instance, it can get saturated with copper and slow down which can result in long etching times and pitting or undercutting or worse. When I'm etching a board with copper chloride, I'll pour a couple extra inches of solution into the container. It's reusable anyway, and the extra exposure to oxygen just regenerates it. Live large.

2) Don't make too much. As you keep re-using the solution, you're going to need to add a little more acid and a little more peroxide every once in a while. If you've got a 750 milliliter container, start out with less than 500 milliliters of solution. Give yourself some room to grow over time. After all, the main point is to avoid having to dispose the copper in spent etchant.

3) If you've got too much volume of etchant (it will happen eventually) you can evaporate out the extra water by putting it in a shallow (non-metallic) pan or beaker or whatever and letting it sit for a while. This concentrates the copper in solution, giving you a stronger etchant. It'll also re-oxidize some of the copper for you, a bonus. Remember when you're adding the peroxide that you're actually adding 97% water.

4) The linked website suggests that the acid levels in the etchant are not critical as long as there's some acid in solution to do the CuCl2 regeneration. The amount of CuCl2 (vs CuCl) present is easy to diagnose by the color of the solution. Add oxygen to re-green, and add a bit of acid if that's not working. Worst case is that you may have to wait a few more minutes per etch with a sub-optimal bath. This isn't rocket surgery.

5) I do have an aquarium pump ($6 at fish store) that I've used to re-activate my solution. Sometimes I'd leave it on for a few hours while I'm at work if I've been etching a lot. But lately I've been lazy/impatient and tossed in a couple capfuls of peroxide. Both seem to work just fine.

6) The environmental benefit of etching with copper over ferric lies mostly in not having to dispose of the copper that comes off your boards every few times you etch. When and if you do end up with too much copper etchant, please treat it like the hazardous waste that it is -- look into your local hazardous chemical disposal options. There's no getting around the fact that copper salts are (for instance) poisonous to fish even in very dilute concentrations.

Step 6: Alternative (overly-complex) Method: Make Cupric Chloride Faster.

When I originally started trying to make Cupric Chloride etchant, I hadn't thought of just using the regular procedure of etching to get there. So I deliberately dissolved a bunch of copper from a wire.

I don't think it's a particularly good idea, but here's how I got to the end-stage etchant faster.

I mixed the acid/peroxide 1:1 instead of 1:2. The idea was to have a bunch of acid leftover for later regeneration. I don't think it's a good idea, and I wouldn't do it again. 1:2 is probably better, and results in more copper in solution faster with less fuming.

To control the fumes, I used the patent-pending (just kidding) Two-Pint-Glass Fume-Containment-Apparatus. Pour in the peroxide, add the copper, then put one glass on top of the other. Pour the acid down through a small gap between the two glasses and re-seal. Voila. No fumes. (See video. I think I did it with water as an example.)

I also kick-started the formation of cupric chloride by first making copper oxide, which turns to cupric chloride just in the presence of acid alone. This isn't necessary at all, but it was fun. Heat up a coil of copper wire on the stove to red-hot and you get a flakey coating of copper oxide.

Otherwise, it's basically the previous procedure, so just see the pics for notes. I wouldn't recommend it anyway. The less copper you dissolve, the less copper needs to be (eventually?) disposed of, and the acid/peroxide etchant is plenty easy to use.

The two-cup technique is cute. I still recommend it.

<p>Will this work on silver?</p>
<p>The pool acid I obtained was 14,50%, about half of what the article mentions. I decided to try the 2 to 1 ratio mentioned. So I should have about half the acid. My expectation was that the first etches would be a little slower than the two minutes mentioned. First etch took about four minutes, so it was easy to manage. I guess that you could do a 1 to 1 and have the quicker etch but I liked this result.</p><p>Can anyone with experience or knowledge comment on the long term viability of this solution?</p><p>This first circuit board was made with Sharpie ink as the resist. Depending on your skill, this can be a workable (but perhaps sloppy) technique.. If you try it, paint the traces twice (nice and black). I got a little etch thru on a couple of my traces.</p>
Could you use this in knife for stone washing and hamons?
<p>Works really well except when it gets cold it seems to become 100% worthless like rewarming it did nothing, have to swish it around a lot until I get a air pump. Would a coffee warming plate be a bad idea to try and rewarm it with?</p>
<p>This is a neat method. I would suggest looking into the 'sponge bath' method that another person used for Ferric Chloride etching. That method should work with these chemicals and allow one to make only enough to etch the current project plus not overheat everything because you have control over how much etching is going on at any given time. </p><p>I would not want to risk putting that much time and money into making a pc board and then have it etch so fast that it overheats everything. You might be a little apprehensive about putting your hands actually into this stuff, but use a slower reacting mix and it should do fine.</p>
<p>Thank you very much Elliot for this Instructable. I was able to get<br> my solution (2 parts hydrogen peroxide 3% and 1 part Hydrochloric Acic <br>38%) and mixed in a very short time and began etching. My PCB turned out a dream in only a few minutes.<br><br>I<br> used a pyrex glass 1 litre jug as the mixing bowl with that sitting in a<br> bowl of water to help cool the solution if things got too hot. No <br>fuming at all, stripped the 4&quot; x 3&quot; pcb leaving just the circuit behind <br>in just a few minutes.<br><br>A couple of questions though as I am not that strong on my chemistry.<br>1st.<br> The peroxide I used is from the supermarket medicine section and the <br>solution turned brown when I added the acid. I am guessing there might <br>be some kind of dye in the peroxide solution?<br><br>2nd question, in <br>the prepratation for this I found some 12% hydrogen peroxide at the <br>'beauty section' and as it was a lot cheaper per volume than the 3% from<br> the medical section I brought a bottle of that. It is a 'creme <br>developer' and contains other chemicals. specifically CETEARYL ALCOHOL, <br>SODIUM LAUREL SULPHATE, PHOSPHORIC ACID, ETHANOL, METHYLPARABEN<br><br>I<br> am worried about mixing this (diluted with water down to 3% peroxide) <br>with acid. Has anyone else tried this sort of solution before? I could <br>not find any straight hydrogen peroxide at 12% that was liquid like the <br>3% stuff from the medical section.<br><br>Price difference is 4 bucks for 200ml at 3% vs 10 bucks for 1 litre 12%</p>
<p>There is a pure 12% hydrogen peroxide available, but it is expensive by comparison. You can google it. I would not recommend using that peroxide you found with that other stuff in it! To make the adjustment from 12%, you do ratios 0.12 per unit vs 0.03 or 12/3 = 4 so you need 1/4 as much 12% to get the equivalent of 3%. Then adjust the volume for the amount you want to mix. <br><br>As far as the acid/peroxide turning brown, it sounds like you got some sort of reaction - were you using Muriatic acid, or something else (a combination cleaner of some kind)?</p>
<p>I can't really get 30% hydrochloric acid, but can you use 10%, and then just make a 1:1 mixture, or something like that? My hydrogen peroxide is 3 %.</p>
<p>Hydrocloric acid is also called 'Muriatic Acid' and you should be able to pick it up easily at any pool shop (used to lower the ph) or hardware store (cleaning cement off bricks etc) in the stronger concentrations. I can't comment on using the lower concentration HCL at 1:1. Did you have any luck with it?</p>
Well, when I tried it 1:1, it just went really slow, and just almost didnt do anything. I decided to pour in some more HCL (about 3 times I believe) but after that it still took a few hour to completely remove the copper from a small piece of circuitboard. Next I will try to use only HCL to etch, and see how that goes.
<p>If you have 10% and you need the amount that would be required to equal 30%, you just do ratios. So you need 3 units of 10% to equal 1 unit of 30%.</p><p>Adjust the total amount of liquid volume to get the right volume. So 2 units of peroxide with 1 unit of 30% gets 3 units of volume. To adjust that to use the 10%, you need 3 units total so 3 units of 10% plus 2 units of peroxide is 5 units 3/5 + 2/5 = 1 so 3 units would be 9/5 + 6/5 or 15/5 = 3 units. Put another way, you need 1.8 units of 10% acid and 1.2 units of peroxide to make the 3 units, not 1:1. So your etchant should have worked considerably slower at 1:1.</p>
<p>I did this, and the results were amazing! Etched a test pattern in 2 minutes. The only difference was that I used 9% Hydrogen peroxide. The starter solution etches very fast and heats up a little bit, so I had to put the container with HCL+H2O2 into another container with cold water just to keep things cool :D </p><p>P.S. The distance between the black marks in the second pic is 1 mm.</p>
<p>I will second the &quot;things getting hot&quot; comment.</p><p>From my initial research, I was being cautious so I put my plastic mixing jug inside a larger heavy-duty plastic detergent bucket (picture 1). I also had a water hose, some extra containers, and other stuff on hand.</p><p>I though I was going slow on the initial mixing, but there was still enough heat in the solution to start melting the inner jug. Visually, it looked like the bucket was collapsing sideways, melting, and shrinking. I immediately added a lot of cold water from the hose into the larger bucket, which stopped the melting process. Luckily, the inner jug retained the solution with no leaks. The second picture is the now cool but damaged jug.</p><p>After the solution was cooled to ambient temps (around 70F on that day) I transferred the solution to a larger spare jug, then continued to combine the remaining 31% HCL, 12M (40% ?) H2O2, and copper wire. </p><p>While the water in the large bucket looks blue (picture 3), it is because the blue solution in the new jug was making the clear water appear to be blue colored as well.</p><p>Picture 4 is the final green solution after dissolving some of the copper wire, and another view of the melted jug. Notice the condensation on the inside of the large jug, which is the fumes from the solution condensing on the air cooled plastic wall.</p><p>Picture 5 is the aquarium air hose used to bubble air through the darker green solution. Normally this was sitting in the heavy bucket seen in the rear, but I pulled the mixture out to take this picture.</p><p>Picture 6 is the now emerald green solution after adding Oxygen from the air bubble hose. You can see more copper wire sitting in the solution, as I was continuing to test to color changes compared to the copper etching speed.</p><p>Picture 7 is test of preparing a single sided PCB for etching. I had painted the entire PCB, and then used a laser to burn off the paint wherever the copper is to be removed. The paper shows the Gerber copper pattern, while the laser is still in the process of burning off the paint. I had to jump through hoops the generate a negative of the Gerber output for the Laser, as the black lines on the paper represents where the mask paint is to remain on the PCB. Note the left 75% represents one circuit, and the right 25% is another circuit, allowing the board to be split apart if desired (only one set of power and ground traces cross over the vertical &quot;cutting line&quot;).</p><p>Picture 8 is the first test of etching a board. The size of the etching tank didn't allow the entire board to fit, so the small circuit side was cut off before etching began. The three large holes used to attach the board to a plastic &quot;stirring stick&quot; using a zip tie. That allowed for manual agitation without having to reach directly into the heated solution. This board was left in the solution too long, so there is significant undercutting of the pattern. As a first test, I noted a number of process improvement to make (temperature control, move even agitation, improvements with work space lighting, etc.). However, there was enough copper left to make the board work by adding a few wire jumpers and bending some leads over missing pads so they connected with traces before soldering. The full design was double sided, but the missing top copper was only for jumpers, so wires were used to replace the missing top copper. This hand-etched PCB worked well enough to fix a some minor trace errors (flipped DB9 pin connections; incorrect pinouts in the CAD parts library) and prove the overall circuit worked before sending it out to a professional PCB fabrication house.</p><p>Picture 9 is the first validation test of the professional board. The fixes based on the hand etched board resulted in this final PCB working correctly the first time.</p><p>Picture 10 is a general setup shot prior to mixing the etchant solution. I using the 40% H2O2 solution, so the 2% solution went unused. I blocked out the one bottle since it would have been dangerous to add to the other chemicals, since it was used to clean the PCB copper prior to masking and etching.</p>
<p>Best to do your mixing in a glass/pyrex container, and then transfer it to the plastic storage after it has cooled.<br><br>The last time I made enchant, I did it outdoors in the middle of an adjacent field, in glass, and with a face mask because you don't want to be breathing that hydrogen, and the chance of an errant spark/flame is less likely.<br><br>When you're done making it, you can slowly funnel it into a plastic jug inside of a bucket (in case it tips over while you pour it). <br><br>This stuff will make any metal in the room rust quickly if left open, or is stored in an improper container. I have my last batch stored in a yard/pool container with a flip top lid, along with the leftover acid I used to make it.<br><br>One day I tossed a few scraps of stainless steel in the box for some reason or another. When I came back several months later, most of the stainless steel is rusted on the surface. There isn't much plating left.<br><br>Before I started storing the acids outside in their own container, the vented caps would allow the acid into the air, and my tools were rusting like crazy from the open air.</p>
<p>You might try as Darrell_H suggested, putting the container in a bath. You might also want to make that bath a very icy one and give the etchant solution time to cool down to the temperature of the bath before putting the board in. In some cases this can slow chemical reactions and if nothing else it will help dissipate the heat faster.</p>
<p>wow. Neat</p>
<p>Will this work to etch aluminium? would i have to put some copper in it first?</p>
I have used it to etch aluminum... It causes a thermal reaction and gets pretty warm and bubbly, and etched quickly. It was already used etchant. I'd do it outside of your going to try it, fumes a lot too.
For aluminum, the HCl that we're using here will work just fine just by itself. Look up &quot;aluminum foil hydrochloric acid&quot; on the web -- it's a well-known way of producing hydrogen gas, but the aluminum gets eaten up in the process.<br><br>The downside of the reaction is that it creates heat, and speeds up (creating more heat) as it gets hotter. If you're reacting a lot of material, you're going to need to cool it or else you'll end up with runaway boiling hydrochloric acid in large quantites, which is about as fun as it sounds.<br><br>I would call etching aluminum with HCl a strictly-outdoors activity, with lots of cool water in buckets on hand if things go wrong. Because of the hydrogen gas it produces, you want to make sure there are no open flames anywhere nearby. I'd experiment with diluted acid solutions first.<br><br>OTOH, it's a great way to fill party balloons with hydrogen. :)<br><br>
<p>Great idea. I'll have to try that. Glad you relabeled your bottle. My first thought when I saw the photo was this... https://www.youtube.com/watch?v=xIMPbPDwj_g</p>
<p>nice work! How do you dispose the solution finally?</p>
Let it dry up or neutralize with baking soda and take it to your local hazardous material center. You never want to pour down the sink or throw in the yard, the dissolved copper is highly toxic to fish and other animals.
<p>Hello! The muriatic acid I have says to dilute the acid with water at a 20:1 ratio. Do I still do this prior to doing the hydrogen peroxide mixture at 2:1 or is the peroxide what dilutes the acid and I don't use any water at all? Any help would be greatly appreciated! Thank you!</p>
Follow the intsructions in the instructable, not in the muriatic acid... So no, do not dilute
This looks great! Im a jeweler and I'm going to try it, but I'm wondering if this solution works on brass, just as ferric chloride does?
Works on brass, but the etchant gets gunky, so I use a separate container for brass
<p>Could I Use high power electrolysis instead of an abrasive when etching? Theory being that running a current through the HCL will let it pick up the copper ions very easily- especially at high currents. This would allow makers to have super fine traces without the worry of brushing them off, or having them wilt off over time.</p>
There are a million ways to skin a cat. (Gross!)<br><br>I do 10 mil traces with toner transfer all the time now. I've run a couple boards at 6 mil, which is the design limit for a bunch of the cheaper overseas PCB factories. The etching is not the limiting factor -- it's getting the etch resist uniformly and reliably on such small features.<br><br>I agitate the boards constantly in the tank -- meaning swishing the etchant around, not rubbing on them. I've never had problems with damaged traces. <br><br>OTOH, if the electrical idea ends up a good replacement for swirling, I'm all for it. Tipping a tupperware back and forth is boring.<br><br>So yeah. Try it out -- you might hit on an improvement. Let us know. <br>
<p>Would this solution etch a 4&quot; x 9&quot; piece of 360 brass plate?</p><p>I'm trying to etch decorative markings onto the face of 360 brass. </p>
<p>The mixture is 2 parts peroxide, to one part acid. But always pour the acid into the peroxide. The initial reaction in my experience has been about a 20 degree temp increase.</p>
<p>I do a lot of custom circuit designing, and building. I started using this mixture over two years ago, I would never go back to ferric chloride again. I have a 3 gallon tank to do larger boards, and use an aquarium air pump to keep it fresh. When needed I top it off with a little acid, as in instructions. Mix it properly as it does get warm during the mix.</p>
Could I mix copper II chloride with HCL and get the same result? I have a lot of copper 2 chloride the Blue Rock looking stuff laying around. if you're not sure I may just try it and see what happens.
1 finger is a single two is a double ! Ok my cup is 300 ml !<br>How much do I use? 25ml is a finger 50 is two .<br>Six fingers is a Cup.<br>Wagons do not travel in uk only on Television a long time ago.<br>Nice is Nice but time has passed and that is the problem.
<p>I understand your frustration that the US didn't move fully to metric system 30 years ago. Try living here and dealing with both systems side by side, all the time. If the loss of the Mars Climate Orbiter spacecraft mission (costing about $300 million USD) due to mixing up English and Metric units isn't enough to move us toward a metric only nation, I doubt any complaints in an instructable will have much impact.<br><br>That said, adding fingers into the equation doesn't help much. Try the conversions listed here instead:<br>https://en.wikipedia.org/wiki/Cup_(unit)</p>
<p>What really gets me is when reading a recipe for something and I ask the author &quot;is that liquid oz or by weight?&quot; and I get &quot;WTF the difference?&quot; in return. The measured substance not being water.</p><p>Add to that UK ounces, US ounces and troy ounces (in jewelry).</p>
<p>Pretty Cool this is.</p>
<p>Everyone must be using 1/2 Oz boards because I mixed up a batch as stated, kept it heated to 74 deg F, and it took 4.5 HOURS to finish a 1&quot; x 6&quot; 3 Oz board! By finish it was a pretty green, and the next board took 6+ HOURS even with agitation and sponge wiping! Either I can't read or you all use micro thin copper. I did try a new batch with 1/2 Oz copper, and a 1&quot; x 1&quot; piece still took a half hour with constant agitation. Doesn't stain so that is nice, but I could have CARVED the boards with a jacknife in that time!</p>
<p>1) How much liquid did you make? A few shot glasses of liquid is no likely to have much etching capacity. Maybe you need more liquid volume?<br><br>2) Unless you live somewhere cold, 74F is only &quot;room temperature&quot;, so will not have much effect. The solution needs to be warmer.<br><br>My initial batch was about 1-2 liters in volume. Using some loose copper, the clear enchant went emerald green in about 20-30 minutes at around 65F (it was fall, and I was working outside). You could see the dark green haze of the removed copper as it went into solution.<br><br>After mixing the solution, I used a &quot;retired&quot; crock pot to make a heated bath. The ceramic pot avoids problems with using the acid in a metallic pot. Once used this way, I will never use if for food again, and painted warnings to never use if for food (in case someone runs across the crock pot later, and I'm not there to stop them from cooking with it). At low heat the bath temperature was around 100F. Fumes are stronger as the temp goes up, so extra care not to breathe in the fumes is more important. I have seen commercial gear refer to temps in the 110F to 130F range, but at the high side of temps the material the equipment is made from is more has to be more durable to withstand the higher temps. I wanted to stay in the range of &quot;hot tub&quot; hot so if I needed to handle stuff during a problem/issue, I would not run the risk of a bad _thermal_ burn through my gloves. Besides the obvious goggles and gloves, I kept a large bucket of fresh water nearby to quickly dilute/cool issues that might come up.<br><br>As the etching progressed, the color turned very dark green, which is the bath reaching it's ability to etch well. I used an aquarium air pump to bubble air through the solution overnight to add the oxygen to turn the solution back it emerald green. Adding extra acid/peroxide can recover the solution quicker if you don't have the time to air air, but it will increase the volume of solution. The air regeneration keeps the volume about the same over time (minus any H2O evaporation that occurs to slowly reduce the volume). <br><br>I was using a single-sided 1 oz copper board, 4&quot; x 7&quot;, removing about 90% of the copper cladding. Board was pushing the size the pot could hold (keeping the flat board covered in liquid in an oval pot), so I was agitating the board in the bath manually using a plastic stick attached to be board. I could see the end of the board on the far size from the handle and the top side compared to the bottom was etching faster. Since I could not get a really even agitation, the far end seemed to be getting more local fluid movement, and the top was probably more pronounced as lifting the board and down was probably caused more solution turbulance on top near the surface of the pot compared to the bottom. I have not yet had time to create a vertical bubble tank to see if the agitation can be made more even.</p><p>IIRC, the first board took about 40 minutes, and a second board about 25 minutes. I was working in a garage with an air temp around 50F. I left the lid off for the first board, so the bath cooled down quite a bit during the etch. I left the lid on between agitations the second time, helping to keep the bath hotter. Fuming was more noticeable the second time around as well.</p>
<p>I forgot to add, after etching, I transfer the liquid into a thick walled, all plastic container that can be sealed. I air bubble the solution to regenerate it, with the lid sitting on top to help keep stuff from falling in while the air hose with an aquarium air stone is installed. Once the solution is ready for future use, I fully cap the container to seal it up. The ceramic crock pot is too heavy and cumbersome to handle without sloshing the bath, it cannot be sealed air-tight, and is to fragile (ie: breakage) for me to trust for secure long-term storage of a caustic liquid. <br><br>The large plastic jugs used to sell pretzels in has worked well for me so far. I then store that inside an all-plastic cooler just in case the jug ever leaks. The cooler is also marked with &quot;NEVER USE FOR FOOD&quot; since some amount of liquid drips from the first jug during transfers are inevitable, and I don't want to be drinking diluted copper acid of any concentration off the outside of a beverage can in the future.</p>
<p>I'm glad it's not just me.</p>
<p>Thank you for this very useful 'recipe', it worked very well etching heavy (1.5mm) copper sheet using photocopy resist to create dog tags and other jewellery. My only addition to this instructable is- keep the coper flat when etching to get an even etch, I tried suspending a two sided piece in the solution, and although it worked fast, there was a tendency to leave heavy 'flow' marks on the surface- possibly something to do with the debris leaving the surface? Pieces left flat in the tank with some rocking agitation were fine.....</p><p>I will check and see if there is an instructable on photocopy resist, and maybe add one?</p>
<p>This thread needs a professional chemist since you are suggesting using some pretty serious materials here. Concentrated acids, strong oxidants like hydrogen peroxide, and organic solvents like acetone are not to be handled lightly. (Background: I have a Ph.D. in inorganic chemistry and I work with these materials on a daily basis.)</p><p>First, make sure to have proper personal protective equipment: goggles, nitrile gloves, and long sleeves that can easily be removed (think lab coat). Work in a well ventilated area with a sink/hose nearby. If you get the acid on yourself, wash it with water (that scene in Fight Club is wrong, don't neutralize and don't take advice from movies) for at least 15 minutes. Read the safety datasheets.</p><p>Hydrogen peroxide is an oxidant. Acetone is a reductant (fuel, same thing). Don't mix them, they'll burn eventually and possibly rapidly. They can make explosive peroxides, which is a problem if they concentrate and crystallize out. If you do mix them, dilute with water 1000x. This advice goes for mixing hydrogen peroxide with methanol, ethanol, and isopropyl alcohol. Work with small volumes when possible, danger is increased with volume and concentration.</p><p>When you are done, your solution will still be a solution of copper chloride in water. It's hazardous waste and needs to be disposed of properly in accordance with federal, state and local regulations.</p>
<p>Just an FYI: do NOT mix the hydrochloric acid, hydrogen peroxide, and the acetone together. Not that a person would do this...but it's possible someone might dispose of the stuff together or accidentally combine them. It can form acetone peroxide, an unstable (or, at least, very sensitive) explosive. Read about it on Wikipedia, that article explicitly referenced PCB etching with these chemicals. I'd encourage everyone to read it directly and not just take my word for it.</p>
which article and which section is that?
<p>You know Remediate the copper solution with yeast and bacteria from potted soil to absorb and use copper as an element. Since most copper hydroxide and salts are soluble in acids and lye you could use yogurt bacteria to neutralize it.</p>
<p>I am not that &quot;chemistry&quot; astute, other than that I still have in storage from High School. I etch brass and nickle sheets, would this etchant work with those metals too?</p>
<p>Great article - I especially like the fact that over time I could potentially recover the copper.</p><p>I haven't done the calculations yet but I'm thinking of creating a 1:1 ratio of the mix as I plan to buy 12% H2O2 &amp; 30% HCL &amp; that way reducing the water dilution after a few etchings especially when needing to re-oxygenate the mix as I find bubbling air through the mix too cumbersome. I anticipate the initial reaction will create more gas than the 3%/31% mix</p>
<p>instead of hydrochloric acid you can use household vinegar</p>
<p>I haven't done PCB etching in years. Maybe when I retire... Just a thought on disposing of the solution. Since you want to keep the copper out of the environment, could you treat the solution as a plating bath and deposit the copper onto something, perhaps a piece of scrap PC board?</p>
<p>My first attempt failed. I used 200ml pool acid (30% HCl) and hydrogen peroxide (400ml 3% H2O2), and after 20 minutes it turned slightly green, and that was it. After 2 hours there is no sign that the copper is coming off of the PCB. I kept it warm and swished it around for the 1st hour, but it looks like nothing is happening to the board; I just left it outside for now - I'll check it in the morning. I need to get more H2O2 to try to tune the batch, but if that doesn't work, I'll have to go back to ferric chloride.</p>

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