On Sat, 23 Mar 2019 18:41:04 -0500, you wrote:
On 3/23/2019 2:11 PM, Harvey White wrote:
On Sat, 23 Mar 2019 18:26:47 +0000, you wrote:
Received from Dave at 3/23/2019 04:30 PM UTC:
Thank you very much Jim. Great info and very helpful. I really appreciate
it. :-) One question though, when I look up "fritted glass bubbler" I mainly
find bongs. Where is a good place to buy a "fritted glass bubbler"??
At your local pet/aquarium store. A fritted glass bubbler will be all
glass... a glass tube with an enlarged porous end on it. Describe it like
that if they don't understand "fritted glass." You don't want a tube with a
porous ceramic stone glued onto it as the stone is liable to deteriorate in
the solution.
I can almost guarantee it will... Never had any that lasted.
??? ??? That is what I heard so I want to avoid problems of any kind.
Exactly.
If you can't get a tube with a porous glass end, just a plain
plastic tube with an open end will do, tho it will take longer to regenerate.
Shouldn't be hard to find the fritted glass bubbler in any half decent
aquarium store.
If you can't do that, then you can take some standard PVC water
tubing, just a few inches, put an adaptor on that (either plastic in
the mixture, or L the tubing outside, and U it down over the tank
wall), then drill small holes in it. If you want, you could use a
screw fitting so that "experiments" in hole size involve wasting less
material.
Never had a problem with the pipe and etchant.
I do like the idea of the glass bubbler, but I just never found any.
??? ??? Plastic tube will work and it's easy enough to drill holes in
it. But can't we drill holes in glass tubes with our carbide bits?? Or
would we break more of them than its worth? If a person were to try
that, what size carbide would be strong enough without being excessive
in size I wonder?
Actually, it may not be all that easy to drill a hole in a glass tube.
Considering that the PVC pipe works, is dirt cheap, and won't break
under too much pressure (and can be drilled with standard drills....),
I'm wondering why to go through the problems of drilling glass....
Seriously enough, you'll lose perhaps an inch in the bottom of the
tank, and if you put a grille made from fluorescent light grids, you
may miss a bit more.
Then again, those cereal storage containers are fairly deep unless you
want to do 9 or 10 inch boards (including border?) in the tank.
Harvey
Harvey
Jim H
Dave
On 3/22/2019 7:50 PM, Jim Higgins wrote:
OVERVIEW:
This is a simple procedure for preparing 1 liter of cupric chloride etching
solution. The tradeoff for the simplicity is a bit of patience as it may
take a while to complete the preparation. The value of this patience is
that the resulting solution won't be overburdened with hydrochloric acid
and thus won't be as smelly and as corrosive to materials around it as more
quickly prepared solutions tend to be. It also won't have any residual
hydrogen peroxide which will result in a very slightly lower tendency to
undercut your PCB traces. That last effect is really quite small, but why
not? Also, since we won't be depending on the presence of H2O2 once the
etching solution is prepared, we don't have to worry about over diluting
our solution by trying to regenerate it with the weak 3% H2O2 commonly
available in drugstores. We'll be regenerating with an air bubbler, which
can serve double duty to agitate the solution when etching.
MATERIALS:
One large (at least 2 liter/0.5 gallon) glass container with a plastic lid.
A 1/2 gallon "iced tea" jar with a plastic lid (plastic liner or no liner)
and a small pop open spout would be ideal because you can open the spout to
insert a fritted glass bubbler for use in rejuvenating the solution after
use. If you need more than 1 liter (1 qt) of solution, consider using a
larger container and increase the amounts of materials below accordingly. I
suggest the container be only about half full when done. Only partially
full plus a small opening in the lid keeps any spray resulting from
regeneration by air bubbling inside the glass container.
One small aquarium pump. The cheap vibrating kind is fine.
One fritted glass bubbler, preferably long enough that it can reach the
bottom of the large glass container with at least an inch or more of glass
tube sticking out - preferably. If you can't find one that long, then your
plastic tubing will extend into the container. I don't like that, but
that's just me.
Plastic tubing to connect the pump to the fritted glass bubbler. I like
enough tubing that I can place my pump higher then the top of my jar. Not
likely the solution will syphon out if the pump is lower, but it's 100%
impossible if it's higher.
200 grams (7 oz) copper wire, copper pipe or other pure copper. I used
solid copper wire, but stranded copper will dissolve faster for those in a
hurry. Pennies (even the old type) and misc plumbing hardware aren't pure
copper and are unsuitable. 200 gms of copper is about 14 feet of #10 copper
wire.
Hydrochloric (muriatic) acid concrete driveway cleaner, free of detergent
or other additives. (Read the label.) This should be 32 - 37% HCl. Weaker
will work, but will require more. You can get this at Home Depot, Lowes and
assorted hardware stores. It will probably cost more at pool supply places.
Hydrogen peroxide. The typical 3% solution from the drugstore is fine. You
only need a few ounces.
SOLUTION PREPARATION:
Pour 1 liter (4-1/4 cups) of water into your container and mark the level
on the outside of the container. Pour out the water. This is the level you
will want to maintain later after etching and rejuvenating.
Add the copper to the glass container.
Place 0.6 liters (2.5 cups) of hydrochloric acid in the glass container.
Add 0.1 liter (0.5 cup) of hydrogen peroxide. This should be all the
hydrogen peroxide you'll ever need.
The copper wire will begin dissolving as evidenced by a green color forming
in the solution and bubbles being generated on the surface of the copper wire.
Place the lid on the container, open the spout and insert the fritted glass
bubbler connected to aquarium pump and begin bubbling to mix the solution.
Here's where patience comes in... continue bubbling until the copper wire
is completely dissolved. If the solution becomes a brownish, possibly
muddy, color, add 1oz of hydrochloric acid and continue bubbling until the
wire is completely dissolved AND the solution is a deep emerald green. The
color will be fairly dark, so hold the solution up to a bright light, or
pour a bit into a smaller container, to gauge the color. If the acid you're
using is on the weaker side, you may need to repeat the addition of a bit
(less than an ounce this time) of HCl if several days of bubbling don't
result in a deep emerald green color with no trace of a brownish or muddy color.
Dilute to 1 liter with water and that's it.
Use it as you'd use any solution to etch PCBs and pour the used solution
back into the main glass container when done. Inspect for color each time
you pour solution into your etching tank. (It should be easier to gauge the
color in the etching tank because you won't be looking thru as much
solution.) As long as it's emerald green or only slightly off color, it's
good. No harm in bubbling to rejuvenate after every use, but not necessary
until it's no longer a pure emerald green.
The amount of excess HCl in the solution is designed to be quite low to
none. If excess HCl is present there's no avoiding some of it being driven
off by bubbling, but at very low concentrations that amount is essentially
negligible. For those whom I might consider overly concerned... you can
have the greater peace of mind you desire by avoiding unnecessary
rejuvenation... and when HCl must be added because the solution won't fully
rejuvenate, you can add it in smaller increments than I recommend until the
solution can be rejuvenated to a pure emerald green.
At some point you'll find you can't rejuvenate just by bubbling. When that
happens, add 1oz (less if highly concerned about corrosive fumes) of
hydrochloric acid and bubble until emerald green. Add less than an ounce if
worried about corrosive fumes, but realize you may need to add several of
those smaller amounts to fully rejuvenate.
Maintain the solution level in the glass container at 1 liter - or whatever
your initial volume was by adding water if it falls lower. If you only add
HCl very sparingly, you can easily find the volume of the solution doesn't
increase because some water evaporates when bubbling.
Over time, depending how much etching you do, copper will build up in the
solution. When this occurs you can remove a bit of solution (maybe 0.5 - 1
cup), pour it into a pint jar and set it somewhere to evaporate. Make up
what you remove with water. If you accumulate any significant amount of
copper chloride crystals in this jar, you can scrape it into a small
freezer baggie and give it to someone who wants to use it to kick start his
own etching solution. Just dissolve it in water and add a small bit of HCl
and you have etching solution. Add copper wire to it and bubble air thru
it, adding HCl until the wire dissolves and you have stronger etching
solution. A weaker solution will etch a PCB, but may undercut a bit due to
the much longer time it will take.
That's it.
Jim H
