Stop using Ferric Chloride etchant! (A better etching solution.)

Picture of Stop using Ferric Chloride etchant!  (A better etching solution.)
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.

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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.)

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m-m-owen2 days ago

Followed directions using 200ml 3% hydrogen peroxide and 100ml 31.45% HCL (muriatic acid). Worked perfectly and exactly as described. Good stuff. Way cheaper than the ferric chloride I have been using and I dont have to heat it.

Newton25 days ago
Tried this method this morning and it worked like a charm. Messed up the mask a bit but nothing that cant be fixed.
The Real Elliot (author)  Newton14 days ago

Not bad! And awesome for a first run.

Are you using toner transfer? If so, I'd say your iron is running a little hot b/c of the smudged-out pin holes. Try using more pressure (lean into the iron with your full body weight) and less temperature and see if it's easier to get consistent results.

If you're feeling really experimental, you can run a bunch of practice prints reducing the temperature each time until you get a transfer that's not smudgy. No need to waste copper board by etching each trial either -- just wipe away with acetone and try again. You should get the proper temperature dialed in within half an hour.

Tanks for the feedback. Definitely giving this another try. I think I got the wrong transfer paper as it took forever to transfer to the copper. But time will tell, I'll post another pic when the next one is done.
Victor8o52 months ago

Hi, I've noticed that the mix I've made releases small bubbles, resembling champagne ones, even thought there isn't any copper inside and the last reaction took time hours ago is this safe?

The amount of bubbles seems to be very low, but it keeps going for hours.

As a precaution measure the lid is a bit loose to avoid pressure to build up inside.

Hydrogen Peroxide decomposes to water and oxygen spontaneously; that'll be what you're seeing. So it's pretty safe.

It happens faster when exposed to light, which is why it's sold in dark bottles.

JLDohm1 month ago

If you want more concentrated H2O2, is is available as "Clear Hair Developer" in the drug store with the hair dyes. 10 Volume is 3%, on up to 40 volume which is 12%.

rizoma made it!2 months ago

Hi, thanks for the tutorial, I successfully etched my first board today, before that I was using a cnc from a friend avoiding etching cause the concerns of disposing the acid etc, so the idea of the recycling etch was really amazing. Even thou seems that most people don't get it, and just like this recipe for the fast first etching...

I just did a little test, it was great, I got 15% hcl and 3% h2o2 I started mixing by 1:1, no etching so after 5 minutes I added another part of h202 and the etching started, took less then 5 minutes. Great.
I used a little glass bottle for the enchant, but after reading some comments now I'm afraid it could explode for the pressure, but I don't won't to leave it open cause I'm afraid it would loose it's effect... any advice for storage and for the next pcb? I would like to do the best I can for re-use everything the best possible way. I want to use a acquarium pump too...
ps. I think I got just 25ml of total for this little board picture attached.

mykiscool2 months ago

I found one that just uses vinegar and peroxide. That's as cheap and safe as you could get!

Ananse152 months ago

What metals will I be able to etch with this solution? I usually work with brass, copper and nickel silver blanks.

dkamegawa2 months ago

Reporting results after first use: this thing is sick, in the best way. Money for roughly 1.5 litres of this stuff set me back the same as a small (250ml) bottle of FeCl3. Roughly twice as fast on the first use, and if it can be reused almost indefinitely, this means I won't have to buy more chloride ever again. Piece of advice for everyone, this thing's quite friendly for toner and should be awesome for serigraphy (haven't tried) but it's very destructive on sharpie lines; try to make at least 3 layers of marker beforehand, because this tends to wash away the ink rather fast.

mkeen854 months ago

what is the minimum percentage HCL acid needed?

I can get 33% online, but is a bit pricey.

but i can get brick cleaner from local shop which is a lot cheaper but is only 10-15% HCL

The Real Elliot (author)  mkeen854 months ago

My recipe calls for 34ish% acid (10M) and 3% peroxide (97% water) mixed 1:2. This means the resulting acid is diluted by a third (one part in three total parts) and so is around 10%.

You're starting out with around 10% acid, so you can't really afford to add too much peroxide. If I were you, I'd experiment with straight 10% acid, and tossing in a few capfuls of peroxide at a time. Or maybe I'd go as far as a 1:1 mix of weaker acid and peroxide. Or maybe try to find some strong (10-15%) peroxide so that you don't have to water the mix down as much.

Either way, experiment. The worst that'll happen is that it doesn't work very quickly, but even with a weaker acid solution you should get etching. Post back with your results?

thanks i think i can get some 10% peroxide but would 30% hydrogen peroxide be over kill?

also once i have made the copper chloride could i boil it down then add more HCL to make it stronger?

If you do go down that road (attempting to concentrate the Peroxide) be *very* careful as it will become extremely caustic (chemical burns for you) and once past 80-90% concentration, it becomes explosive. I made a mess in a college chem lab by neglecting to watch some hydrogen peroxide I was boiling down. Thankfully, nobody was hurt.

The Real Elliot (author)  mkeen854 months ago

30% peroxide _is_ probably overkill. But then again, too much overkill is never enough!

On the other hand, boiling the acid is probably not a good idea. The stuff (at 3M) is nasty enough without being hot and spiiting.

If you need to increase the acid concentration, one way to go is to simply leave it sitting out in a shallow tray. The water evaporates. Done.

double_g mkeen854 months ago

I bought some 31% Muriatic acid at Home Depot which was $4 (or somewhere around there) for a quart. I think they had it for pool supplies.

I'm not a chemist, but I would think that 15% would work, but your etching would take longer. You'd probably want to double down on HCl in the recipe above so you'd be adding the same amount of HCl as you should.

mkeen85 double_g4 months ago

thanks I will try that.

fschonholz6 months ago
So ... I have been experimenting with your technique and it is cool. As a first time etcher ... this made it easy. I have been having an issue with the "mask" (not sure what it is called technically) to etch. I used shappies and nail polish. The shappies have been useless. The nail polish has been a hit and miss, as some of the nail polish stays, some gets eaten away and some half way.

I build guitars and wan tot do one with an aluminum front that is decorated. I want the decorations to be etched out.

The question is, what should I used to "draw" the decoration that I do not want the acid to act on? and what should I use to protect the back of the plate I want to etch so only the front is etched?

Thank you!

The easiest and cheapest way is to just get a letter-size magazine you no longer care about, torn apart a few pages and print the art over them with a laser printer (ink does not work). Then iron (yes, an actual iron) the printed page over whatever you want the art to stay on for like 25-30 minutes and remove gently with water.

Thank you for the assistance. I actually found the way to do it using nail polish ... just needed to find the right nail polish.

If I want to etched in the design, I paint the full surface with nail polish and then scrub out the design. If I want to etch out, then I draw the design with a market and then pain it with nail polish.

You can find the results here:

It is a bit rough for a first try; but just an excuse to do more :)

I have always used the toner transfer method, print what you want on photo paper. Lay the paper with the print upside down (toner facing the copper), use an old iron to melt the toner on it by putting it on the paper for a minute. Lay the board with the paper on it in a bowl of water (the paper should stick to the board, before you lay it in the water). Rub of the paper, and you have a very nice etch resist. Only works on laser printers.

nov8 fschonholz6 months ago

I found the best and most precise way is to take a vector file of the design you want to a print shop and have them make a decal. It’s pretty durable. It costs more than a Sharpie but saves on frustration. For the back of the piece I usually use electrical tape. But just recently I started using wax. Just melt it down and pour it on the back of your piece. It's cheaper in the long run and is re-useable. When you are finished I found the best way to remove the wax is to put the piece in hot water to soften, then peel it off.

apappano4 months ago

On the chem page, Google is detecting malware on the original Adam Sechelle site. Here's a reposting of it:

May want to update the link until it gets fixed.

akro1235 months ago

Thanks sooo much, this was my first time etching, and i didnt bring enough money to radioshack to buy the etch lol, this worked great!!

Sylentskye9 months ago
Is there a way to do this using vinegar and hydrogen peroxide (peracetic acid)? Would it be safer than using the muriatic acid? What ratio would you suggest to start with? (I have white distilled vinegar and both retail 3% and hair salon 30% hydrogen peroxide solutions available to me. Thanks!
The Real Elliot (author)  Sylentskye5 months ago

With vinegar (a weak acid) and 30% (strong!) peroxide, you're doing it all backwards. Instead you want essentially a strong acid with sufficient available oxygen.

Try the recommended recipe? It's worked for like a bazillion people.

It will technically work, but it might take days, or even weeks. It would be much safer than muriatic acid, but the only real danger of muriatic acid is that the fumes will hurt your lungs, and will rust any metal objects in the room.

If you are going to use vinegar, hydrogen peroxide is a great idea to add oxygen to speed up the acid reaction. Change the vinegar often; it will quickly become full of copper acetate, leaving little room for the vinegar to do its work. Add heat; put the reaction in a bowl of hot water or over an electric blanket or central air vent; just a few degrees Celsius can mean the difference between days and hours.
bezo885 months ago

nice work. I tried this design and it did not work. I used 1 part vinegar and 1part hydrogen peroxide and salt. I was testing to see if it works and I left a small pcb and a few pieces of copper wire in the solution overnight and it did not dissolve , it just got rusty and nothing happened to the pcb.

The Real Elliot (author)  bezo885 months ago

I've heard the vinegar suggestion a lot. I'm not a fan, and I don't understand the point.

For the chemical reactions involved, you really just want an acid -- a source of hydrogen ions. HCl is about as simple an acid as you can hope for, in terms of availability & purity & strength. It's un-dangerous enough that it's the acid of choice for regulating swimming pool pH. Good enough for me.

With vinegar you don't really know what you've got, chemically. All sorts of flavor compounds and colors? Residual sugars? Yuck. No thanks, give me cheap and pure hydrochloric any day.

freedomdivine5 months ago

HI I use the Ferric for etching metal jewelry. I buy it at Radio Shack its pretty pricey! Could you please tell me if this would work just the same on my metal jewelry? Thank you so much.

The Real Elliot (author)  freedomdivine5 months ago

No idea -- depends on the metal.

But acid + peroxide are cheap. Why not try it out and report back? This is one of those frequently-asked questions: a bunch of people will be interested to know how your experiments go!

ProMaker5 months ago

Not sure why others are having trouble. I just tried this technique for the first time and it worked perfectly. 3% H2O2 from Walmart (32oz bottle $.99) Muriatic Acid/31.4% HCL from Lowes (1gal. $7.29). Mixed it in the garage although fuming was so little probably could have done it in the basement with no issues. Etched in a small glass jar at room temp. and applied agitation throughout. 2"x3" double sided 1oz board etched in about 4 mins. Solution started clear and ended a light emerald green.

bobh92866 months ago

I started using this method today. I had a board I wanted to etch so I followed these instructions to the T. The board I am making is 2" x 6" only has a circuit on one side but the board I got is plated on both. My first run at this was an ugly failure. With a brand new batch of the etchant it took over an hour to remove all the copper on the side with the circuit and this resulted in a very pitted circuit that is unusable. No big deal as always expect a first time failure :)

On my second run it still took a good 30 to 45 minutes to etch the circuit side of the board and there was still at least a third of the copper on the other side. At this point I pulled the board and just sanded the remainder of the plating off. The board looks nice and is ready to go.

My concern is the length of time this appears to be taking. In earlier posts and reply's I see comments that if it takes longer than 15 minutes or so to etch a board something else is wrong. What could this be?

1st Board.jpg2nd Board.jpg
pilgrimsc8 months ago
hello can you tell me if this would be good for etching carbon steel?
DEEPAKP131110 months ago

The shopkeeper is being a jerk. Ask him for "muriatic acid" or "brick cleaner" or "hydrochloric acid for cleaning bricks". The concentration strength for cleaning bricks is the one I used for etching PCBs.

However, ANY concentration will work! Some will just take longer than others!
thefeeb moeburn9 months ago
I wonder if this is the reason mine is taking so godawful long, then. I tried this last night and after an hour of soaking, I barely had an image. I bought a gallon of muriatic acid from Ace Hardware. Even with the basement window and doors open, it got thick with that acid fog. Could it be the brand? Seems the pros are outweighed by the cons in my case... frustrating.
moeburn thefeeb9 months ago
You also have to watch the temperature. This is a chemical reaction, and chemical reactions are highly affected by heat; in this case, if it is below 20°c, it will take days. If it is 20-25°c, it will take a few hours, and if it is 30-40°, it can take just a couple hours. So if its a little chilly where you live, and your windows are blowing cold air over your acid, then you need to place the acid bowl/container in a bowl of hot tap water to speed it up.
thefeeb moeburn9 months ago
Thanks for the quick response! I was using the Hydrogen Peroxide, but I wasn't heating it... which I was unsure about. I have kept Ferric Chloride heated, as all tutorials outline, but I hadn't seen anything about temperature in this tutorial (sorry if I missed it!), so you've given me more to troubleshoot, thanks!
Also- I'm pretty sure I've read that getting the transfer, which I'm also struggling with, is easier if you turn up the resolution/blacken the image to get more toner, correct? I bought a laminator specifically for transfers, but it's been pretty spotty. I just read one tutorial that underscores the importance of pre-heating the copper, as ironing it directly will cause condensation, contributing to spottiness/areas of poor transfer. I'm surprised at how much of an art this seemingly simple process is turning into! :)Big thanks again!!
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