Black Rhodium Plating

Jewelry Discussion
1

I have a customer that saw a piece that he says was gold with a
matte black finish. In searching through teh archives I came across
posting for black rhodium. Could someone give me more info on this.
Iunderstandits not as durable as white rhodium, but this may be worth
following up on. Anyone know where I could get some in the US?

2

I have been pen-plating sterling silver with black rhodium for about
2 years now, and here is my experience:

For gold- and rhodium plating I use “Rhodinette, fiber electrode
plating system” a german make pen-plating outfit. I buy the rhodium
bath in 100 milliliter bottles. They are rather expensive, such
bottle costs about $ 100.

  1. After rhodium plating, the jewellry will retain the same surface
    structure as the silver had before plating. So, when I need a glossy
    black surface, I must glossy-polish the piece before plating.

  2. Room temperature is important. I never heat my liquid Rhodium,
    but I try to keep the roomtemperature 23 degrees centigrades or
    higher, at least one hour before I start plating. This gives all
    liquids the same temperature.

  3. Degreasing is also very important. After ultra-cleaning and
    drying, I dip the jewellry into 10% sulphur acid solution for a
    minimum of 3 minutes, (herafter no fingerprints on the surface to be
    plated! I use latex gloves), then I wash it thoroughly in tepid tap
    water, and dry it with clean kitchen roll. After plating, wash and
    dry as usual. I do not use this sulphur-solution for pickling! I
    prefer to use tapwater rather than destilled water, because the first
    is always fresh, while the second will slowly contaminate. The water
    quality here gives me no problem.

  4. Cleanliness is alfa and omega when plating!

The “Rhodinette” comes with small glass-containers, colour-coded for
each plating-bath. When washing the containers, I use distilled
water. I only pour as much rhodium bath into the container, as I
estimate to use in one plating session. I never pour the bath back
into the bottle again. If the liquid in use becomes contaminated I
will ruin my stock, if I pour it back. Unfortunately, “Rhodinette”
has it’s own scale of electrical power, which goes from 1 to 10,
instead of using voltage, so I never know how strong current I’m
using. Naturally I go by the instruction booklet but I also do a
little experiment to find the best voltage for my job.

I use my “Rhodinette” both for black rhodium- and gold plating For
each kind of plating, I use seperate felt-tipped pen. These come in
different colours too, and should be kept apart. The rhodium bath
contains acid and the gold bath contains cyanid. As we all know,
these two things will produce a rather nasty effect, if mixed.

I like my Rhodinette, but there are other makes out there, probably
just as good. Further info.: www.wieland-industrie.de -and here the
adress to the US agent:

“Landa International”
10, West 47th Street
Lower Level
New York, N.Y. 10036
Phone: 212 944 4944
Fax: 212 921 2412

They can probably supply the baths as well.

Jon H. Holm
3740 Svaneke
Bornholm, Denmark

3

hello ZACH,

you can buy black rhodium of companies like UMICORE or COHLER (which
is U.S.based).

UMICORE has black RH product (471) which i prefer the most as it is as
durable as white RH.

as for sourcesyoucan find them on company websites i.e.:

USA UIC Technical Center
Mr. DonWalsh
240 Town Line Road
Southington, CT 06489 Tel: (00 1-8 60) 793-40 11
Fax: (00 1-8 60) 7 93-40 20

thanks,
Hitesh Satikunver
Tanvi Arts
Mumbai (India)

4

hello Jon,

i admire the way you explained every minute details. your post is a
ready recknor to anyone starting RH or any kind of plating.

i must say that though i am doing rhodium plating for years,i
learned a thing or two.

i wanted to ask you some questions to share knowledge and also to
upgrade it.

a) you said you dry pieces after ultra and befor 10% pickle, is
drying necessary and what is the impact of it on final result?

b) do you do cathodic cleaning in an alcaline cleaner after ultra ?

c) i presume that you must have done Black RH by bath plating
(dipping) too,have you noticed any difference between bath and pen
regarding colour? (because according to my observation in pen i am
getting jet black colour where as in bath the colour is much
lighter)

d) is genuine BLACK RH available out there,because generally
RUTHENIUM is used in place of RHODIUM ?

using tap water in place of destilled is a totaly new thing to
me, may be you dont have chlorinated tap water that must be the
reason.

thanks,
Hitesh Satikuver
Tanvi Arts
Mumbai (India)