Which is the best hobby do-it-yourself method for making PCB's?

No it doesn't, and nor does unreadable.

You need to become familiar with a dictionary.

-Chuck

Actually I didnt need to take this step at all. The car repair shop (where they offer 15 minute oil changes)was more than happy to add the ferric cl to his contamination/waste disposal binge/bottle/whatever.

I stopped by for an oil change and transmission flush and noticed the sign "waste disposal fee - $1.20" and I asked the guy what it was for. He replied ... that they charge to dispose the contimated engine oil (I thought that was PART of the oil change cost) .. in any case I casually asked if I could bring in a FeCl I have accumulated in a large snapple plastic bottle and he said sure

I brough it in and mentioned "hey be careful that stuff will eat through flesh and metal" and he replied "calm down, I know exactly what this stuff is"

So I will be tak>> Good point.

The RatShack FeCl jugs used to (still do?) advise you to flush it down the toilet after it's used. Sounds reasonable to me... a little iron, a little copper.

John

Wow! That really is a bad idea! FeCl is basically harmless to nature, in small quantities, but put it in with oil, antifreeze, and other gork, and you now have real toxic waste.

The folks that pick up this guy's waste are expecting certain contaminants to be in the oil, but not FeCl. If they find out about the FeCl, they will not be able to recycle the oil. They will have to send it, at great cost, to a toxic waste disposal processor.

The FeCl will go directly to the bottom of his waste oil tank, and stay there regardless of how many times the tank is emptied and refilled. It will surely etch a hole in the bottom of the tank.

-Chuck

I can't remember the details now, but I vaguely recall some method to rejuvenate used FeCl.

...Jim Thompson

However, ferric chloride is very easy to chemically alter, so it is almost completely inert in the environment. Just neutralize it with washing soda (sodium carbonate) till it quits fizzing. Then all iron and copper chloride will have been converted to almost insoluble iron and copper carbonate mud. Then you can flush it down the toilet.

Roughly a ounce of copper, diluted by maybe a billion gallons of water, won't harm anything. More copper is leached out of household plumbing every day in any good-sized city than you can reasonably dump from household pcb etching.

John

I think the copper compound in spent etchant can kill the 'good' bacteria in a septic tank system, for those out of reach of municipal water-treatment systems.

Best regards, Spehro Pefhany

At that point, the proper thing to do would be to filter through some paper towels, and throw the solids into the trash. Copper compounds are extremely poisonous to fish and plants.

My whole point was that dumping the FeCl into a tank of used oil, just because the stupid mechanic says you can is well... stupid. You, and the environment would be better off if you dumped the waste onto the ground, and let it kill some weeds, or trees, that you don't like.

Flushing it down the toilet isn't a real good idea either, the FeCl does a number on the cast iron pipe that lives in many plumbing systems. Many moons ago, I worked for a PCB manufacturing house. They wouldn't allow me to recycle their spent FeCl (the supplier would give me about $1/gallon for spent FeCl, two carboys was worth more than I made in a day's wages) They dumped the waste FeCl down the floor drain in the building, and then had to bust up the floor every other year to replace the sewer pipe.

If you dump the FeCl into a sink, it will eat out the brass traps, without regard for how much water you flush down the sink... ask me how I know ;-)

-Chuck

Hence the need for pre-neutralization with washing soda. It will do nothing to pipes after that, except, possibly line them with a bit of mud.

Add hydrochloric acid and oxygenate with air bubbles. But it eventually becomes cupric chloride (green instead of golden brown).

OK, dumb question time - does this work with sodium bicarbonate as well? Or is it maybe not recommended because of the H in NaHCO3?

I have a confession to make - I had enough of the RS stuff to be about an inch deep in a 9" x 12" cake pan, and I just dumped it down the storm drain, which leads to the ocean, so I feel so guilty I should probably turn Liberal or something[1]. ;-P I had done one double-sided board, if that makes any difference. And the only heat I used was to set the pan in the driveway in the sun. :-)

Cheers! Rich [1] I'm a smoker, and when I'm, say, walking down the street and finish a cigarette, if there isn't an ashtray or trash can handy I'll put the butt in my pocket until I get to one. :-)

Which sounds kinda like it'd be the same color as the bit of mud they get lined with already. ;-P (ever disconnected the dump hose of a trailer that's been sitting in a lot for 3 years? Eww!)

Cheers! Rich

(snip)

It works just fine. But you might be surprised how much a quart of ferric chloride will consume, and how much gas it gives off. You can but a big box of washing soda lots cheaper than the same amount of neutralizing ability with bicarb. You can also use calcium carbonate (limestone). With either sodium bicarbonate or sodium carbonate you get salt (sodium chloride from the reaction. With limestone you get calcium chloride, the stuff that is sold to melt ice from the sidewalks.

Make that, buy a big box of washing soda...

Of course, but if I routinely dump it, and you routinely dump it, and someone else dumps their favorite stuff down the drain, sooner or later it adds up. Like you, I truly doubt that there are enough hobbiests that use ferric chloride to etch PCBs so ever make a difference in the ecology of the sewage treatment plant.

As an interesting side note, WSSC, the local water and sewer company, for a couple of years used ferric chloride as the flocculating agent for their water purification process... and surprise!! after a couple of years of doing that, the copper plumbed houses in their district started getting pinhole leaks in long horizontal sections of the copper pipe.

Imagine!

-Chuck

Yes, you already said that, and if you will notice, I wrote FeCl, not iron or copper carbonate.

-Chuck

Any municipal water treatment system I've ever heard of uses a "biological" cleaning stage using bacteria -- so it applies here as well. Yes, and it is the copper solution (the Cu++ ions) that are toxic. I don't know just how insoluble the compunds are that you create by adding soda. But if you indeed create some "mud" on the bottom of the container, with the rest of the solution not having any greenish or bluish tint, it's a good start.

robert

The water is very close to colorless when the mud settles.

According to this table, copper carbonate has a solubility constant of about 1.4*10^-10 and iron carbonate has a solubility constant of about 3.2*10^-11. Both are essentially rock dust.