Hello,
I am about to get some organic objects gold plated and would like to
know if there is some way to know how thick the coating of gold is.
I would like to get a heavy coat and of course the shop will say "
Yes, it is a heavy coat and charge accordingly BUT is it true? Is
there any secret way to know what they have done is the truth or
not?? What I am plating is a bone substance and how thick do I need
the gold to last a long time and how to make sure it is the
thickness I need?? HELP!!!
Sharron who is preparing for a well deserved vacation in search for
beads, good silver and gold wire, and good tools in the cities I
will be visiting in S.E. Asia
Sharron, I would suggest that one way to approach this would be to
find a respected plating shop and enter into dialogue with them. How
long gold plating will last is not just a function of the gold
thickness, although obviously thicker lasts longer than thinner. The
other consideration is the gold itself, and how pure it is. A lot od
work has been done on creating “hard” gold plate for items that take a
lot of handling, and it could be that one of these would be better for
your application than a layer of pure gold. A respectable shop should
be able to advise on the best approach in your particular application.
As regards the question of determining the thickness yourself, if
this is still necessary. Printed circuit board manufacturers
routinely use XRF (x-ray fluorescence) to measure gold thickness in
the micron range, and I ecpect a good plating shop might do the same
(although they probably just go on time and current). Either you have
access to XRF or you dont, you can’t cobble it together on the kitchen
table. The only other way I can think of, which is also used
industrially, is to cut a section and examine it under a microscope.
Kevin
Hello Sharron:
There are some technical methods to measure the thickness of the gold
plating. You have to take the object to a metallographic laboratory
specialized in such analysis. There is more than one method to
determine the thickness. Some are destructive and the others are not.
The firsts destroy or dissolve the object and leave the gold plating
intact in order to weight it accurately. The others methods are less
destructive, such as microscopic measuring, but the object is cut in
several pieces, and it doesn�t disappear at all. They can give you
back the body. And there are others that can measure the thickness
using some equipment using ultrasonic , magnetics, induced current,
thermoelectric, beta and X-ray radiation method, and there must be
some new that I don�t know. I can tell you what I do without going to
a metallographic laboratory. I make a comparison. It is a mix between
a wear off and thickness measuring. I need to have in my hands a gold
plated object that you know is a very good one. Take a rubber, the same
students use in the school. Better if it is for ink, that is hard. Rub
a little portion of the surface, with the same pressure and rubbing
only in one way. Count how many times you have to do this until you see
the base metal, a clear change in color, this should be the nickel
that is the metal that generally covers the base metal. Now that you
have a number, you can evaluate your object, for comparison. It is not
the best way, but you have an idea. There are some gold platings that
are hardness than others, but there is not so much difference. Gold
baths have cobalt, nickel, copper, cadmium, silver to obtain certain
hardness and color. Gold plating needs to be applied on a more hard
surface to last more, and to prevent corrosion of the metal base. The
choice is almost always nickel. The thickness you want to have for
your object is the final sale price. After 10 or 15 microns of nickel
your object should have at least 2 microns of gold to assure six
months of wearing without the problem of the gold disappearing. This is
a low limit. You can start from here when you make numbers. You have
to raise this value if we are talking about chains. I can extend this
explanation with more details if you need. I have been gold plating
for many years and I prepare my own salts and baths.
I hope this can help you a little,
Regards from Daniel Mischelejis
Buenos Aires, Argentina
email: mischelejis@fibertel.com.ar
web page: http://www.mischelejis.com
Sharron,
I just finished an article for AJM Magazine on plating quality
control and how jewelry manufacturers can be assured that they’re
getting what they’re paying for. (If you’d like a copy of the issue
(May 2000), just drop a note to ajm@ajm-magazine.)
The bottom line is to be absolutely certain, ask for X-ray
fluorescence testing, and ask them to provide documentation that the
test has been done. (Others have done an excellent job describing the
process, so I won’t duplicate their answers.) Increasing numbers of
platers in the U.S. are performing the service: some routinely, some
for an additional charge. Most will send it to an appropriate lab if
they don’t have in-house capability. Many will also be happy to
discuss their other quality control procedures with you, such as bath
maintenance, to give you a better idea of how your job will be
completed.
But be sure to ask these questions up front: not all platers use
these high-tech solutions, and quality control methods vary greatly
from plater to plater. If gold thickness is important to you, having
the conversation up front is the best way to prevent unpleasant
surprises.
Suzanne
Suzanne Wade
writer/editor
SuWade@ici.net
Phone: (508) 339-7366
Fax: (520) 563-8255