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>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>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>
<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>
<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>You should add this to your Instructable as many people seem to be having this issue. :)</p><p>By the way, great 'Ible. I want to try PCB etching one day so this might be just the right solution! ^^</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>I'm glad it's not just me.</p>
Hi I am new to etching. Is the ink a special ink? Would like to know so that I buy from this ink.<br>Thanks
<p>Would this work with 9% H2O2 and 18% HCl?</p>
Yup. I'd go one-to-one with those concentrations, though. Should be ballpark right.<br><br>I
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.
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>As Sugarim say's it's about proportions.</p><p>IIRC, cups are used in American cookery and their use arouse during the 1930s recession (the method may hark back to the wagon-train times?), since one can make a recipe without the need of scales. I think that strictly, cups are based on fluid ozs, but in this context, it doesn't mater, you could use watering cans, shot glasses, clogs, or any container! One simply changes the cup size, or multiply the number of cups to scale up or down. Very smart!</p>
<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>Having been a long-term user of FeCl, I stopped making PCBs due to the issue of disposing of the waste. I will definitely use this method and start making boards again - Thank you! A great little article. Really useful, easy to read.</p><p>The secret to a good etch is a good mask, timing (watching) and a good quality copper clad board. I found fiberglass boards always gave better results than paxolin etc. Agitation improves speed and evenness of the etch, bubble etching is very good and in this case would help maintain the strength of the etchent.<br>As to the quality of the resist mask: Photo etching in my experience is best, but again the quality of the original photo mask is important. I know that there are many methods. The best quick method for 'neatness' and the ability to print from CAD that I found, was inkjet onto mat acetate, ink side presented to the board to ensure less fuzzy edges - the acetate will hold the pattern away from the board and allow light to erode the edges if you have ink uppermost; after that comes laser on laser safe acetate (multiple copies stacked). But the best for quality is the 'transfers and tape' method onto acetate (or directly onto copper), since they are very opaque and have good edges, they produce a sharp edge. Again, photo mask against the board before exposing if using acetate.</p><p>CNC printing with an XY plotter, using etch resist/or light resist pen is best method for speed/quality and the ability to draw from CAD. Photo resists are usually made 2x size, but of course require specialist projectors.</p><p>One last thing to help you make easy-to-use PCBs - Tin Plating crystals! Another nasty chemical, but a well cleaned board that has been tinned is a dream to solder! It comes as a powder, just add water! It lasts and lasts.</p><p>However.... Especially for multiple boards, you can't beat a professionally produced board complete with solder resist mask and ink layer. You may be surprised how cheap this can be. All you need to do is send them your PCB file. Maybe not as satisfying as creating your own masterpiece though.</p><p>May I make one comment about the article? - over use of the &quot;American Collective Noun&quot;! It's a pet project of mine, please use 'bunch' responsibly! Bunch of flowers/wires - Cool! Bunch of flour/wire/people/liquids/solids/cars/snow/etc. - not so cool ;) :p</p>
<p>Will this work to etch aluminium? would i have to put some copper in it first?</p>
<p>So will this work on knives and swords made out of damascus steel?</p>
<p>I made this today it works great. Have found that transparency film works great for toner transfer. If you use transparency film after you heat it for a few min let it cool all the way off then you can just peal the film off. I got in a rush the first time and pulled a few of the traces off. Lesson learned make sure that the pcb is cool to the touch before removing the film.</p>
<p>nice work! How do you dispose the solution finally?</p>
<p>This is very useful and I&quot;m going to try it for etching copper jewellery. What resist should I use? Will a Sharpie work?</p>
Sharpie is an OK resist, but not a great one. If you're going to try to etch deep, like you might for jewelery, something stronger might be a better choice.<br><br>Fingernail polish? What other thick / lacquery paints do you have on hand? Electrician's tape? <br><br>Or just experiment. :) <br><br>Some people bake Sharpie ink lightly to make sure it's totally dry beforehand, and that's supposed to help. I just wait 5-10 min or so.<br><br>Let us know how it goes?
<p>This is a great tutorial, I like that you explained the chemistry and gave a recap! I can't wait to try it! I'll be using it for sculpture similar to jewelry applications. </p>
<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>
<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>

About This Instructable


1,359 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: