I recently made the jump from perf board and decided to etch my own boards via toner transfer and using murialtic acid and hydrogen peroxide and lets say that the first board I made came out great! But then I go to etch another board and instead of etching fast like the first board it doesnt etch at all and I mean I left it in there for hours and nothing. The bath is transparent green and as I read is normal. Now the time frame since my first board and this board was a week and I did store the etchent in a covered tupperware container. I was wondering if it was due to the fact that there was a build up of water weakening the etchent. Could an airpump, say from a cheap fish tank pump, reactivate it and get it up and running again. I did read that you can add peroxide but then again that adds water so I am not sure. I also hear that a little bit of salt gets things going again. Also, how do you evaperate the water out of the acid? Just leave it sitting there with the container open?

Thanks!

 

That etch solution has a very short shelf life.. Just make up a batch as needed.
Its just to cheap/easy to make not to just do that..

But yes you could try bubbling air through it to attempt to regenerate it.

 

I have read that too, but people praise it for being reusable. It is rather cheap enough that I can do that just fine but would hope that I can get it reactive.

This guy says it is reusable http://www.instructables.com/id/Stop-using-Ferric-Chloride-etchant!--A-better-etc/?ALLSTEPS

 

I know that hydrogen peroxide will decompose into water and hydrogen gas when exposed to light (that's why it's always sold in an opaque container), perhaps this is what happened with your solution...

 

I do know that when I opened the container back up there was a lot of water evaporated on the lid. Perhaps that is what was going on. I do my etching in my basment so there is no light when it is stored even if stored in the open during the day. I decided to leave the containers out, in a high place in the dark and open to see what happens to the water vapor. Then I'll go get a cheap fish pump from walmart and see if introducing oxygen to the etch will get it going again. Maybe maybe not. I read that some have success and others do not. I also read to add salt ( not a whole lot ) but some. I wonder what that does. Maybe soaks up the water in the solution?

I read that someone took a straw and just blew bubbles into the salution, I'd rather not.. I do not think Hydrocloric acid would taste all that awesome.

 

HCL is pretty good for clearing stuffy nose. Accidentally I poured some HCL in alu. lid which I though that was plastic....Well 5 minutes later room was full of black smoke and my nose was cleared,Perfect!

You could simply go out to the store and buy HCL its pretty cheap.

 

I read that someone took a straw and just blew bubbles into the salution, I'd rather not.. I do not think Hydrocloric acid would taste all that awesome.

Not to mention the fact that you'd be blowing mostly carbon dioxide and nitrogen in, when the point is to oxygenate the solution.

I followed the same instructions on that Instructables page and I have no problems, but it does take quite a while after I've done a few etchings, and the time depends on the size of the board. Yes, it takes longer the more you use it, but also note that the page mentions how you can periodically add a little more. It kind of 'refreshes' it.

I don't know how effective this is, but my method of trying to oxygenate it is to shake the crap out of the bottle, open the cap to get fresh air in, shake the crap out of it again, repeating this a few times. One time I had borrowed a small oxygen tank from a friend for beer making purposes, and used that.

 

HCL is pretty good for clearing stuffy nose. Accidentally I poured some HCL in alu. lid which I though that was plastic....Well 5 minutes later room was full of black smoke and my nose was cleared,Perfect!

You could simply go out to the store and buy HCL its pretty cheap.

Oh yeah, you know what else is great for clearing a stuffy nose? Tear gas! I do have a full gallon of HCL so I am going to add some more of that along with the proper ratio of Peroxid

 

Not to mention the fact that you'd be blowing mostly carbon dioxide and nitrogen in, when the point is to oxygenate the solution.

That is what I thought. You don't exhale Oxygen but rather Nitrogen and carbon dioxide. Maybe he thought that it just was working the whole time.

 

I know that hydrogen peroxide will decompose into water and hydrogen gas ...

Not hydrogen, it liberates oxygen when it decomposes into water.

HCl and aluminum will give you hydrogen gas. Not sure how any black smoke was formed.

Stomach acid is hydrochloric. I'm not sure of the concentration used for etching but at high dilution, it would just be sour and not have much taste. You don't want it near your body, skin or mouth if you don't know the concentration is safe (low).

Exhaled breath isn't much different in composition than ambient air. (That's why mouth-to-mouth works.) Yes, you take out a little of the oxygen and add quite a bit of carbon dioxide, but it would still have enough oxygen to regenerate the solution. If bubbling air works (and I don't know anything about this), then bubbling your breath would work also.

 

Not to mention the fact that you'd be blowing mostly carbon dioxide and nitrogen in, when the point is to oxygenate the solution.

Where in the world did you get such a silly idea? From Wikipedia for exhaled gases: http://en.wikipedia.org/wiki/Breathing



Carbon dioxide does not interfere with the reaction whatsoever. However, I do agree that for safety, it is better to use an air pump or make new reagents. One might consider an ozone generator, but the ozone output of such things is pretty meek.

John

 

Compare that to ambient air. It's not much different; 21% O2, 78%N2 and 1% everything else.
The bubbling process isn't going to hinge on 21% versus 16% O2.

Oh crap, I thought you were saying my post was silly. Never mind.

 

Not hydrogen, it liberates oxygen when it decomposes into water.
[...]

Good catch, that's absolutely correct! That's what I get for not verifying it and relying on what I remember from something I learned over a decade ago.

 

It may help you to remember it if you recall that one application of hydrogen peroxide is to act as the oxidant in torpedos. I believe the fuel is good old diesel oil. This is WWII-era. They've probably come up with something fancier by now. Anyway, I was surprised when I first learned this. The stuff you buy in the drugstore is, of course, much more dilute.

 

I don't think I ever said it was reusable. I get good results from it, and it is EXTREMELY cheap. What else do you want?

2 gallons of Muriatic Acid, $13. Large bottle of H2O2, 50¢. Supply should last decades.