Gold Plating

What determines the depth of a gold plating?

I am using my new plating solution with a gold anode and it seems to work.

What I don't understand is how long to continue the plating. Does it
keep getting thicker forever? If I plate the part the next day, will it
be twice as thick?

js

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Jack Schmidling wrote:
What determines the depth of a gold plating?

I am using my new plating solution with a gold anode and it seems to work.

What I don't understand is how long to continue the plating. Does it
keep getting thicker forever? If I plate the part the next day, will it
be twice as thick?

js

hi Jack,
In principle, if everything else is equal, yes,
twice as long is twice as thick.
also yes, you can continue for ever or till the gold in solution and/or
the anode runs out.
My plater had to deposit some fine silver 1/4in thick on a special job
recently and it was in his tank for a week.
To check for thickness with out the trade radio active measuring kit,
you use the rub test.
this takes some brass metal polish or car T wax on a cloth and rub
the plating back and forth with your indexfinger till your through the
plating.Count the rubs.
Repeat when in tank twice as long, should need twice as many rubs..
Basically a rule of thumb? method. Can only give you a very rough guide.
How long you plate depends on usage of the plated item.
thats up you you.
On bulk plating say 1000 elecrical contacts, its done by total weight
before and after plasting and unit area calculation. Measured in microns.
OT, how are the Dorset sheep? eaten them yet?

Ted Frater wrote:

My plater had to deposit some fine silver 1/4in thick on a special job
recently and it was in his tank for a week.

I thought there was some physics that would prevent this. So if I plate
my cup inside for an extended period, I could get a measureable
thickness? Something that would not rub off using your test?

Why not make it very thick then for single items?

On another note, my wife's cup came out gold but chalky looking. I
didn't polish this one first so I assume it is the finish on the cup not
something in the plating. I am only concerned with the inside, BTW.

If what you say is correct, I should be able to plate until the pits are
filled and eventually get a shiny finish. I did not thing this was
possible.

OT, how are the Dorset sheep? eaten them yet?

One is in the freezer and a big disappointment. All the myths about
mutton being strong are just that. I did everything to this guy to
produce gamey flavor but it still tastes like veal.

Today is a big day for the other one. His marriage has been arranged
and his bride is being delivered this morning. She is a dark Merino so
we should be able to get a really nice blend of wool from the two and he
will have a gay old time. Much more fun that he is having with the
castrated goat.

js

--
PHOTO OF THE WEEK: http://schmidling.com/pow.htm
Astronomy, Beer, Cheese, Fiber,Gems, Sausage,Silver http://schmidling.com

On Thu, 02 Mar 2006 08:23:01 -0800, in rec.crafts.jewelry Jack Schmidling
wrote:

Ted Frater wrote:

My plater had to deposit some fine silver 1/4in thick on a special job
recently and it was in his tank for a week.

I thought there was some physics that would prevent this. So if I plate
my cup inside for an extended period, I could get a measureable
thickness? Something that would not rub off using your test?

Why not make it very thick then for single items?

On another note, my wife's cup came out gold but chalky looking. I
didn't polish this one first so I assume it is the finish on the cup not
something in the plating. I am only concerned with the inside, BTW.

If what you say is correct, I should be able to plate until the pits are
filled and eventually get a shiny finish. I did not thing this was
possible.


Ted is correct in that the longer you leave an item in a plating bath, the more
metal is deposited.

But it's more complex than that in terms of what sort of deposit you get.

Electroplating's deposit thickness is due to a combined factor of time AND
current density. While we use voltage as the easy method to set up a usual
small plating bath, the actual factor being set is the current density, such as
"amps per square inch", or whatever equivalent units you wish to use, such as
milliamps per square foot, etc. The rate of metal deposition is dependent on
the time, current density, and efficiency of the bath (which itself depends on
the chemistry, amount of metal in it, etc.)

Now, the thing is, current density is not uniform in a plating bath. Raised
convex areas, and especially convex edges and points, attract the current. So
corners and raised areas will plate thicker than recesses and the bottomsof
pits and grooves. In a simple bath, one result is that as you continue to plate
longer and lonter, you get roughness and actual nodules forming, rather than a
more and more level surface. Think about how, with higher voltage, arcsrun
from points (like lightening rods, for example), more than depressions tohelp
visualize this. It's the same on the micro size level.

There ARE things that are done, commercially, to control this. Additivescalled
brighteners work by causing the bath to be self leveling,l essentially be
limiting the deposition in high current density areas so the lower current
density areas catch up. This type of bath does indeed come out brighter and
brighter. Most commonly are found brightened baths in copper and nickel,
intended as underplate layers precisely to improve a surface finish before
overplating with gold or something else. Many of the baths intended for
electroforming are brightened baths, and most of the really good systems are
proprietary. But if you want to play with making up your own home brew type,
with a copper sulphate based copper plating bath, play with small amountsof
molasses as the brightener....

The trouble with brighteners is that they are not stable consistant componants
of a bath you just add when first making it up. They get consumed or broken
down during use of the bath, and baths made with brigheners then need to be run
with controls so you know to add a certain amount of brightener after measured
time/amperage intervals. Brightened baths end up being a lot more complex to
run, and more costly. Other than the brightened copper and nickle bathsthat
CAN be purchased in the small quart sized bottles, such as from Rio Grande, I'm
not aware of others marketed in this manner. The others are generally sold to
industrial users in larger quantities, intended for plating lines with much more
sophisticated operating setups.

Normally used gold plating baths are not brightened. In use, as the deposit
gets thicker, it gets duller and rougher. This can be combated to an extent by
mechanically brightening them every so often. Do that by stopping, rinsing the
work, and gently burnishing the plating layer to literally pack down and
brighten that surface. A gentle brass brush, used with soapy water or other
similar lubricant (beer is traditional too!) will brighen it up a good deal.
Just baking soda paste with water on a fingertip will work too, though this
tends to remove a little of the layer. When it looks metallic again, resume
plating.

Also, using lower voltages and current limiting circuits so the plating takes
place very slowly, over longer times, will also give a smoother brighter
deposit. Higher voltage/amperage plating is faster, but produces more
difference in plating thickness between high current density spots and low
spots, so the thicker you end up wanting it, the slower you've got to go,for
best results, at least when using non-brightend baths.

Peter

Jack Schmidling wrote:
Ted Frater wrote:


My plater had to deposit some fine silver 1/4in thick on a special job
recently and it was in his tank for a week.


I thought there was some physics that would prevent this. So if I plate
my cup inside for an extended period, I could get a measureable
thickness? Something that would not rub off using your test?

Why not make it very thick then for single items?

On another note, my wife's cup came out gold but chalky looking. I
didn't polish this one first so I assume it is the finish on the cup not
something in the plating. I am only concerned with the inside, BTW.

If what you say is correct, I should be able to plate until the pits are
filled and eventually get a shiny finish. I did not thing this was
possible.


OT, how are the Dorset sheep? eaten them yet?


One is in the freezer and a big disappointment. All the myths about
mutton being strong are just that. I did everything to this guy to
produce gamey flavor but it still tastes like veal.

Today is a big day for the other one. His marriage has been arranged
and his bride is being delivered this morning. She is a dark Merino so
we should be able to get a really nice blend of wool from the two and he
will have a gay old time. Much more fun that he is having with the
castrated goat.

js

The thickness of the plating is dependent on how much your prepared to
pay in gold cost.
lso plating doesnt fill pits.
As Peter has extensively detailed in his reply, you can only fill pits
with a bright nickel or copper solution.
It aint a perfect world even in the plating one.
Pits can or should be filled with solder and/or polished out.

All lamb or mutton is a mild flavour. If you want a gamey taste, put up
a high fence as in 7ft and keep deer. We call this venison over here,
and can get it from our local butcher. He does venison sauseges too
Fantastic.
The deer run through our fields and come into the garden to eat the
rose leaves. Prefer to see them than shoot them, anyway there owned by
the lord of our local manor.
It wasnt so long ago that youd be deported to Australia for stealing his
sheep or his deer.