Reuseable etchant woohoo!

[MikeH]

@MikeH,

Throwing away the solution is bad for living things because the copper salts are HIGHLY toxic.

Yes.  I know this.  Mainly because I used to work in environmental consulting.  I know all of the little poisonous things floating around out in your backyard.  Of course by "tossing" I meant disposing of.  I don't know about others, but I first neutralize mine with baking soda, then mix with concrete to make little environmentally inert bricks.  10,000 more and I can probably build a house.

What percent muriatic are you using & what is your mixture ratio with the peroxide?

I tested out a bunch of concentrations recently and found that a 1:1 ratio works fastest, but there was little difference between 1:2, 1:3 or even 1:4 (peroxide to acid).  Basically you can pretty much just eyeball half and half.

[MikeH]

alright, i'm a bit surprised that nobody has asked. what about the aluminium enclosures? in theory i suppose i only do a few more boxes than i do circuit boards, so i could use the mix for both. any experience etching the enclosures?

thanks (:

Aluminum etches a lot faster, and will give off A LOT more gas, which you don't want to inhale for obvious reasons.  I'd recommend using a weaker solution and etching it outside.

[bighead]

I tried it and it works great. i got about a liter of peroxide for $1.50 and a gallon of muriatic acid for $5.00. This is cheaper, more effective, and takes less time. I highly recommend going this way rather than ferric chloride.

[darron]

alright, i'm a bit surprised that nobody has asked. what about the aluminium enclosures? in theory i suppose i only do a few more boxes than i do circuit boards, so i could use the mix for both. any experience etching the enclosures?

thanks (:

Aluminum etches a lot faster, and will give off A LOT more gas, which you don't want to inhale for obvious reasons.  I'd recommend using a weaker solution and etching it outside.

faster etching just makes it sound all the more tempting to me! but i think i'll take your advice then. the ferric chloride. i'll make some of this up for pcbs at least.

[Solidhex]

Yo

  I just started using the Muriatic acid/ hydrogen peroxide technique this week. The first bath was awesome as people have mentioned. Quickest etch ever. Today using the same batch practically nothing was happening. Even after I added some more acid and peroxide. I took a break and reread that instructable. The whole oxygen thing got me thinking. I'm using a plastic food container with a airtight top so I put the top on and shook the whole thing till it was foaming a bit inside and bam! it was like kickstarting the etch process. I had been gently agitating the etchant the whole time mind you. I'll try it again and see what happens next time I etch some boards.

--Brad

[darron]

Yo

  I just started using the Muriatic acid/ hydrogen peroxide technique this week. The first bath was awesome as people have mentioned. Quickest etch ever. Today using the same batch practically nothing was happening. Even after I added some more acid and peroxide. I took a break and reread that instructable. The whole oxygen thing got me thinking. I'm using a plastic food container with a airtight top so I put the top on and shook the whole thing till it was foaming a bit inside and bam! it was like kickstarting the etch process. I had been gently agitating the etchant the whole time mind you. I'll try it again and see what happens next time I etch some boards.

--Brad

yeah. i got something similar. the first one was good, but i'm not sure about this thing with it being constantly perpetuating. i left my solution in an open-top glass jar for a couple of weeks. the instructable said that would help to oxygenate it, but no go really. i'm not sure how to vigorously get more oxygen in there. i get the impression that the method wasn't perfectly tested by the author. i think if i constructed some sort of etching machine to rock and oxygenate then it may help out heaps. the most annoying thing is sticking your head over these chemicals for ages, breathing it in, while you are waiting for an etch. if you could sit back and forget it that might help

[Paul Perry (Frostwave)]

If you are etching alumimum, you could just use hydrochloric acid by itself (diluted).

[Eb7+9]

I was eying my jug of used solvent one night and got thinking about recouping the copper ... just for the heck of it, I tried suspending a pair of stainless tweezers from a string into the solution - I left 'em in there for about an hour or so ... pulling them out I found that a bunch of copper had aggregated itself on the surface ... after a fine sanding most of the stuff came off but in a few places it remains as random patches of copper plating giving them a cool look ... I'm sure electro-plating is next - maybe a good way to finish boxes and save the copper from going down the drain ... ??

[hillio]

One thing that apparently no one realizes is that after the HCL/H2O2 etchant has been used once, is that most of the etching from that point on is being done by Cu++ (Cupric (II) Chloride) ions.  The more Cu++ ions there are in the etching solution, the faster it will etch.  The Cu++ ions will oxidize the copper on the board being etched, causing the copper to be dissolved.  At the same time, the Cu++ is being reduced to Cu+, which is not strong enough to etch anymore and is a darker greenish/brown color. So, it's a good idea to use a fish tank bubbler to bubble air through your etchant for a day or so after a few uses to re-oxidize all the copper ions back to the bright green/blue Cu++, so boards will be etched faster, and cleaner.
Also, using a fish tank air bubbler to bubble air through the etchant while the board is etching will make things go MUCH faster.  The etchant that is in contact with the board is saturated with Cu+ ions almost immediately if the solution is not agitated, and the chemical reaction basically stops until the solution is stirred up again.

[darron]

One thing that apparently no one realizes is that after the HCL/H2O2 etchant has been used once, is that most of the etching from that point on is being done by Cu++ (Cupric (II) Chloride) ions.  The more Cu++ ions there are in the etching solution, the faster it will etch.  The Cu++ ions will oxidize the copper on the board being etched, causing the copper to be dissolved.  At the same time, the Cu++ is being reduced to Cu+, which is not strong enough to etch anymore and is a darker greenish/brown color. So, it's a good idea to use a fish tank bubbler to bubble air through your etchant for a day or so after a few uses to re-oxidize all the copper ions back to the bright green/blue Cu++, so boards will be etched faster, and cleaner.
Also, using a fish tank air bubbler to bubble air through the etchant while the board is etching will make things go MUCH faster.  The etchant that is in contact with the board is saturated with Cu+ ions almost immediately if the solution is not agitated, and the chemical reaction basically stops until the solution is stirred up again.

thanks hillio. sounds like good advice. time to get started on a diy etching tank with a bubble tray at the bottom i think...... sweeeeet.

[hillio]

thanks hillio. sounds like good advice. time to get started on a diy etching tank with a bubble tray at the bottom i think...... sweeeeet.

All you need is a small plastic container deep enough to hold enough etchant to cover a board that is standing on edge.  A plastic tube ran from the fish tank bubbler into the etchant is more than enough to agitate the solution while the board etches. Bubble stones or bubble curtains or bubble trays or other exotic contraptions aren't needed at all.

[Wheeman]

I love this stuff. In my area, ferric chloride can be tricky to get ahold of, except through my chemistry teacher.

The first etch went beautifully, the second and third ones were slow. Leaving the container open after each etch didn't help matters much either. Adding a bit more hydrogen peroxide helped a bit, but only makes more and more solution to dispose of.

If I recall correctly, on the last page of the instructable is a link to a study of the etching qualities compared to FeCl₃.

I need to make an etching tank as well...

[hillio]

One thing you can do to make the solution stronger is to dissolve more copper in it.  More copper = more Cu++ ions to do the etching for you.   After the first couple of etches, my original solution got weaker/slower like everyone else's does. I cut up a bunch of copper wire into small pieces and put them in the glass bottle that I store the etchant in.  I drilled a small hole in a spare lid I had for the bottle and ran the plastic tubing from an air bubbler to the bottom of the bottle and turned it on.  It left it that way for about 24 hours, at which point all the copper wire had dissolved. The solution was a much darker green/blue color, but was totally transparent.  I repeated the same thing again, and I now have a pretty powerful etching solution that works very well.  I rarely have to add any acid, and I never add any H2O2.  The only time you need to add any HCL to the solution is when the solution won't regenerate after 24 hours of air bubbling through it.  Then just a adding a little acid and bubbling for another 12 - 24 hours will usually turn the spent opaque greenish brown colored etchant back to it's bright green/blue transparent state.  At that point it is totally regenerated and ready to etch more boards.

[waky]

so, for etching enclosures what would be best  enviromentaly-wise?. if neither ferric nor cupric chloride will regenerate, wich one will cause less harm when dissposed?

Joaquin.

[cloudscapes]

this is so great! especiallyu because I'm out of ferric chloride and was just about to get a new batch (I've been reusing the same quarter-litre for a few weeks).

I'm probably etching a board o nthe weekend, so I'll use this!