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.)

<p>This may prove helpful. </p><p>http://www.chemcut.net/wp-content/uploads/2015/03/Chemcut_Bulletin_8_Cupri_Chloride_Proces_-Parameters.pdf</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>wow. Neat</p>
<p>Thank you very much!!!!!!!!!!!!!!!!!!!!!</p>
<p>I've got a chromed sink tube and want to get at the copper underneath before I start etching. Will this solution take the chrome off for me before I add my vinyl resist and do my etching?</p>
AFAIK, you want to be really careful with chrome. Fumes, toxicity, etc. And this etchant is aimed at copper -- whatever chrome you get off, you'll expose the copper beneath and it will pit like crazy.<br><br>I'd suggest another solution, but I don't know what. Sorry.
<p>Works great! Will be using it at TangibleTec.</p><p>www.tangibletec.com</p>
What etchant do u use sir ?? I used hcl + h2o2 but etching is not good
I used the HCl + H2O2 formula exactly as described in this instructable. I was sure to use the Muriatic acid that is 31.45% HCl and Hydrogen peroxide that 3%.<br><br>I also used Press N' Peel as my resist, as the kind of resist used can make a big difference in the outcome of the etch.
<p>I tried this etchent. I found it did not etch as fast as FeCl3, but worse, it etched my resist. So I will need to investigate different resist layers.</p>
Is this method just for making PCB or could one use this mixture for etching copper jewelry?
<p>It works great for copper jewelry too!</p>
I am now confused. after reading so many comments I just want to do a PCB for a small electronic circuit. <br>what my board is two inches by one inch . seven components four wires it is a light activated
this phone is stopping me from asking the question what is the amounts in Mililtres cups are not standard in UK
<p>Hi, laaaate reply, but here goes... you just need to get the proportions correct... As long as it's 1 part acid to 2 part peroxide, any amount will work. </p>
<p>Hi Elliot, thanks for an awesome tutorial! I had a great time playing mad scientist in the kitchen (place with the best ventilation in my apartment). The solution slowed down drastically over the third try, but I was etching brass, so that could have been the reason. Adding peroxide and doing some sideways agitation did help... however, what helped even more was sprinkling a bit of salt over the pieces. It immediately removes the brownish coating on the surface, allowing the acid to eat at the metal again. </p><p>Also, over here, in India, for Indian readers, the place where you can find the acid is... and I was appalled... at your local grocery store, usually on the same shelf as club soda or cooking oil or other things that go into your mouth. It's called toilet cleaning acid... get the bottle that says &quot;pure acid&quot;. Most of the times, the bottles will have no indication of the percentage, or even what type of acid it really is, which is really not a good thing... but I digress. </p><p>Anyway, here's a crappy pic. I forgot to mirror the text (Darwin's Origin of Species) before transferring, but I sort of still like it. </p>
<p>Also, once done with etching, scrub the piece with a bit of baking soda to neutralize any further reactions. This is especially important if you're making jewelry.</p>
<p>&gt; Please, what is wrong here?</p><p>You haven't given me much to go on, but here goes:</p><p>1) How did you agitate the board while it was etching?</p><p>2) How did you clean the board before etching?</p><p>3) Does it have anything (oil, plastic film, ???) on it?</p><p>4) What strength is the acid exactly?</p><p>5) At what temperature?</p><p>6) How thick is the copper layer? (Although really &quot;hours&quot; is too long for anything that's remotely reasonable.)</p>
<p>I made up the recommended solution 1 pt acid to 2 parts peroxide. I tried to etch a small single sided board 53mm x 73mm it took hours to etch.</p><p>I was very surprised when you mention that a small board in the instructable took only a couple of minutes.</p><p>Please, what is wrong here?</p>
<p>Thanks for this. Off topic but your storage bottle reminded me of this... http://drunkard.com/images/scottie-hooched.jpg</p>
<p>I live in a place where it's impossible to get acids from a drug store. I can only find acids used in detergents or other cleansing material and so forth. So im wondering if there is any product at a normal market that could be used instead of hydrogen peroxide and hydrochloric acid?</p>
Search for vinegar/peroxide/table salt mix. It's about 100ml/100ml/10ml
Chemistry supply house? Hardware store? Or beauty supply store for the peroxide?<br><br>Hydrochloric acid is pretty common. It's used to balance the acidity of pools and to clean concrete. I don't know where you live, but I bet you'll find some.<br><br>The peroxide I used was really weak -- the kind that people often use as a mouthwash. But stronger peroxide mixtures are commonly used to bleach hair, for instance. <br><br>I'd avoid anything with additional additives. You just don't know what will happen. <br><br>(For instance: some people have substituted mostly-NaOH drain cleaners for NaOH, but then it's also got some aluminum flakes in it which make the reaction exothermic, and turn something potentially simple into a safety hazard.)<br><br>Look around more and get the pure stuff. <br>
<p>So I made a batch but am curious about my storage container. Its a glass jar with a glass lid an rubber seal that is closed with the clamp. Hopefully you know what I'm talking about. Will this be okay? I just don't want gasses to expand an compromise anything/break the jar. </p>
<p>So .. pool acid and mouthwash.<br>I read in the Ferric Chloride FAQ, that I need Washing soda &gt;&gt; is it enough of the materials you mentioned ?<br>And, how to test it with a paper ? normal paper and what's the sign that the mix is safe to pour?<br>Thank you,</p>
<p>Don't go substituting stuff! (Unless you really know what you're doing.) Hydrogen peroxide _is_ used by some folks as mouthwash, but that doesn't mean any other mouthwash will work.</p><p>Hmmm... washing soda. I'm guessing that's to neutralize the acid for disposal? If so, part of the point of this etchant is that you will not need to get rid of any of it for a reasonably long period of time (years? a decade?) because it's renewable. So you shouldn't need that.</p><p>And anyway, I'm not sure that knocking down the acid makes it safe to &quot;pour&quot;. You'll end up with a different copper compound, but it's the copper that's bad for water sources. </p><p>I think when people dispose of stuff this way, they neutralize it first and then let it dry out, and then take it somewhere where you can dispose of hazardous chemicals. But again, we're trying to avoid doing that in the first place.</p>
<p>If you have to be careful with the stainless steel sink, does this mean it well etch stainless steel like it does copper.</p>
<p>Thanks works great!!</p><p>I've made a mixture of: 1 cup H2O2 36%, 1 cup HCl 23%<br>and made a simple test pcb. I did nothing to start the process first try was slow but second try was much faster. Because there was already some copper in the mixture.<br>I was able to make a trace of 12mill =&gt; 0.3mm, my printer was the bottle neck.</p>
<p>made this etchant, it worked very quickly clean, no fumes excellent.</p>
<p>Thank you for your project, looks like a good system to me. Do you have a recommendation of what types of plastic I could use as containers for this project? I intend to use it to electroplate graphite painted 3d printed plastics such as PLA/ABS/HIPS/Nylon/TPE, can you think of any issues i might face with any those plastics?</p>
<p>Just one quick question, does the container need to be actively open when using the solution? The reason why I ask is I try to minimize any fumes I can (even when soldering). Like using a small glass pan with modified lid that locks everything air tight as it etches. I don't know if its like a fume pressure build up like smoke would cause, or more extreme like a 6th grade volcano kind of pressure. Thank you.</p>
<p>No problem closing it up as it etches. I always do that so that it doesn't spill while I'm agitating. (I etch in tupperware and slosh it around vigorously.)</p><p>Ziplock bags also make a nice etching tank. Board in, fill with etchant, close, and then lay it all flat in some kind of dish or tupperware in case you accidently break or open the bag. You can agitate the board by smooshing the bag (carefully) like a waterbed, and it's really easy to tell when it's done because you can press the bag up against the board like a window.</p><p>The other advantage of the tupperware + ziplock bag is that you can easily fill the tupper with warm water which will keep the etchant warm and speed up the reaction. </p><p>When you're done, snip off a corner from the bag and you've got a funnel to pour it back into your container.</p><p>Man, I should make an Instructable on that... </p>
For etching Cu try H3Cit + H2O2 with NaCl.
I think I used too much. All I did was create fumes are irriate my breathing. I'm going to toss the batch, air out my house and try again actually using you measurements. I've gotten too used to just winging it on the amounts of things I use.
<p>Too much what? </p><p>Just aim to get the acid down around 3M or 10%. So if you start with 10M / 34% acid, you need to add two parts water (or weak peroxide in our case). </p><p>Mixing a strong acid and water like this makes heat. If you toss water into the acid, you'll get hot acid and that might fume. Don't do that.</p><p>Measure out two cups of peroxide, pour into that one cup acid. Easy enough, but you need to measure and get the order right. </p><p>Open a window anyway, and if you're getting excessive / noticeable fumes rethink what you're doing.</p><p>And if you want to ditch a batch of the etchant before use (no copper dissolved in it yet), you can toss some baking soda into it to neutralize the acid and pour it down the drain with a lot of running water.</p>
can i use sulfuric acid 30% instead of muriatic acid?
<p>Not 100% sure, but I'd say no. </p>
<p>Elliot the first time I tried this is worked flawlessly. Now I used a small tupperware leftover tub and the boards etched in just a few minutes. I tried it again two nights ago, which was a few weeks later and tried using the still very green solution but I played heck trying to get it to etch. I added a bit more acid but it only seemed to work once I added a little more H2O2. The color didn't change much but the board started losing copper at a more normal rate. Since I bought a laminator and couldn't wait to try it out again last night I threw a couple of small boards in the day old solution and the same result. Just wouldn't etch. Left it in for an hour just to see what would happen and nothing. Added more acid and unfortunately I was out of H2O2. The solution was still nice Kool Aid green too. My wife is picking up some HP today at the store and hopefully when I add that the magic will happen once again. The container is only 4 inches square and maybe 1.5 &quot; deep. You think I should use a larger tub?</p>
<p>Same boat, friend! First batch etches like a dream, but subsequent etches, even if same day, don't complete. Seems a bit of a waste if we have to top off with acid AND H2O2 each time (might as well start from scratch, negating the potential environmental benefits)...</p>
<p>TrumanF,</p><p>I am having the same issue as you are, my initial solution was PERFECT.</p><p>I leave it for a few months, not needing to do any PCBs, come back to it and it is barely etching. I used the &quot;bubble in air&quot; method with no luck, out of HP and will grab some but it seems it is only a temp. workaround and not a solution to the problem.</p><p>Were you able to figure out what was wrong? (solution color is LIGHT GREEN)</p><p>Fadi</p>
<p>Help! My attempts only work when I start fresh with HCl and H2O2- when I try to reuse the beautiful emerald green solution, it stalls, and gives me a very bad etch! My solution isn't turning brown, so it has enough oxygen, and it still takes to copper to the rosey stage, so i think it has enough acid. I will try adding more acid, but...</p>
I mixed the acid and peroxide in the correct ratios. I used my vinyl resist and let a piece etch. It wasn't very deep after an hour so I removed the piece. I placed a couple of scrap pieces in the solution for a few hours and they reduced in thickness quite a bit. I then tried etching another piece and it seemed to be slower than the original etch attempt. <br>The solution is still a very light bluish green. Do I need to dissolve more copper in it first? <br>
<p>Blue usually means copper hydroxide, which means that you've not got enough acid in the solution. I'd pitch in a little bit of acid and see.</p><p>How much copper were you initially etching? Was this a PCB or something else? (&quot;Scrap pieces&quot; of what?) It may just be that you've run out of acid.</p>
Indeed it was not a pcb. 16g copper sheeting is what I use in my jewelry making. A piece approximately 1&quot; by 2&quot; with a vinyl resist. It made a decent visible etch initially. I added a I&quot; piece of 1/4&quot; tubIng and about a 1&quot; square piece of scrap to see if that would green it up. Those were quite dissolved after a few hours but after that nothing else would really etch. <br>Thanks. I'll try more acid. Would a 1/1 ratio be better for my needs?<br><br>Added a sample of the pieces I'm making. Some of those were done with ferric.
<p>Yeah, you might try a 1/1 ratio for a new starting batch, but at this point you can just top up with a little more acid and see how it goes. The whole point is to avoid re-starting and having to dispose of the copper solution.</p><p>Maintaining the chemistry (read: enough free acid &amp; oxygen) is part of the trick with this stuff. When brown, add peroxide. When slow / blue, add acid. Easy enough once you get a feel for it.</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>
<p>An hour with agitation is waay too long. Especially with fresh chemicals, it should go relatively fast, like ten minutes or so. You can tell it's etching when the shiny and coppery-colored metal goes in -- in a minute or so, it'll turn a matte pink color.</p><p>Could anything be coating the copper? Try scrubbing the surface with a bit of sandpaper (finer grit is better for not leaving scratches, but if this is just a test...) beforehand?</p>
I've just finished successfully etching my first board! Someone suggested that the peroxide I bought might be dud: even though I bought it new, if the bottle wasn't properly sealed and it had been on the shelf long enough, he said it could be useless - it had happened to him more than once. So I bought another bottle from a different shop, and hey presto! the board etched in a few minutes. I over did it a little bit, probably because I didn't agitate it evenly: I had to wait for a patch in the middle to dissolve. (Don't swirl: rock!) But it works, so from here it can only get better. I think my main lesson is to keep a few bottles of peroxide handy.<br><br>BTW, before my 2nd attempt, I was also wondering if the &quot;gloss&quot; from the glossy paper might have coated the board with an invisible layer of plastic - it seemed possible - but I've now established that that is not the case. The paper works perfectly.
<p>Hey fantastic! I'm glad to hear you got it working, and even more stoked that you found a way that things can go wrong. :)</p><p>Peroxide has a shelf life, for sure. And as you note, a trip to the pharmacy and a couple of bucks can test that hypothesis.</p><p>Re: agitation is key. The center pretty much always dissolves more slowly than the edges, no matter how you agitate (unless you're spraying, but that's another level of complexity altogether). If you let it sit for a second or two, then swirl, you can see brown/black dust coming off the board -- gives you a good idea of whether you're agitating well enough.</p><p>Glad you got it working, and thanks for coming back with the report. Watch out for bad/expired peroxide, y'all!</p>
<p>i use ammonium persulfate. It is in powder form and you mix it with water. It is tranparent so you can see the etch working, it turns slightly blue as etch is working - I use it for etching copper bullet casings, holding the casing with a 'third hand' and putting it into a plastic up with the etching mix. you can see how deeply the etch is going and then pull it out - no fumes, no fuss. I have tried many resists, staz on ink pads with art stamps, black and white prints on photo paper which i then iron onto the casing, hand drawn sharpie pen shapes.... https://www.youtube.com/watch?v=TLf4w1zTpkw</p>

About This Instructable


1,277 favorites


More by The Real Elliot: Clean and Grease your Skateboard Bearings Quickie PCB Production (with Bonus NiCd Battery Charger) Stop using Ferric Chloride etchant!  (A better etching solution.)
Add instructable to: