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Understanding the New MJSA/WGC White Gold Color Index


#1

Have you ever noticed how white gold varies in color? Many folks
think white gold is the same color as rhodium because all the white
gold they ever saw was plated with rhodium. Others who have bought
very inexpensive white gold have seen the “real” color and all too
soon due to a very thin plating job. That can be frustrating.

To address this and other issues Kraftwerks, MJSA, and the WGC all
worked together to form the White Gold Task Force. Kraftwerks had the
easy role, we just held a white gold roundtable to discuss the
issues. As it so happens at Kraftwerks we had Jim Marquart from MJSA
and Chris Corti from the World Gold Council sitting in. Between
those guys and a few key operators and users of white gold we started
something important at that discussion. MJSA and WGC did the hard
parts.

Most of us are aware that the white color comes from the alloy used.
Manufacturers are very aware of the consequences of the different
white alloys. Some of us are allergic to nickel in contact with the
skin. In Europe a restriction was imposed in response to the allergy
suffered by some people. Even jewelry that complies with the
restriction can cause allergic symptoms. As a result non nickel white
gold is often the choice there. If you increase your understanding
you will make better white gold. You will save money too.

In the United States we use nickel 95% or more of the time to make
white gold. The rest of the time we use palladium. Anytime we use
more nickel the jewelry is harder to produce. When we use high
amounts of palladium the jewelry becomes more expensive. A few rare
exceptions exist including at least one patented manganese white gold
from Precious Metals West.

When we reduce the amount of whitener (nickel or palladium) to
reduce the temperatures needed for casting, or the expense, or to
make a more malleable nickel white gold the color is compromised. As
it turns out the key factor to the consumer is the degree of
yellowness present in the finished item. A tint of gray or green is
less objectionable to most consumers than yellow. This is due to the
yellowness of gold and the way the eye works. Shame on the cheater
who rhodium plates over yellow!

To accurately measure the color of white gold the WGTF turned to
GretagMunsell. This is a company that does color science and makes
color samples for all kinds of industries. Paint, ink, paper and now
white gold all can be measured by a color spectrophotometer. The
chosen color technology is the ASTM YID1925. The “yellowness index”.
The higher the number the more yellowness is visible in the sample.

To be called white gold the yellowness must be less than 32. It
would be deceptive to call any gold with a YID at 32 or higher “white
gold”. Call it beige or cr=E8me or tan but not white.

The best white gold color does not require rhodium. This is what we
call grade one white gold. Sometimes the term premium white is used
but we prefer not to use that term for mere color. Perhaps more
expensive high palladium content whites deserve that term. Yellowness
or YID less than 19. For comparison, platinum comes in with a YID of
9.5 and pure silver is in the YID 7 range.

The next grade of white “grade two white gold” has a tone that makes
rhodium optional. Lots of jewelry is made with white gold that is
this color. This is the range from a YID of 19 to 24.4.

The lowest grade of white gold is grade three. YID from 24.5 to 32.
This color requires rhodium plating. Good long lasting plating. This
white has a distinct but slight yellowish tone.

Understand that there was some compelling reason to use this grade
three range of alloys. Expense, or malleability and setting
considerations reduced the whitener to the lowest acceptable amount.
Try anticlastic raising sometime with grade one nickel white and see
what you get. Most likely cracks in the gold and shattered confidence
in the designer!

You can get equipment to find out what grade your white gold is.
MJSA distributes the Color index card with accurate foil samples on a
black background and the calibrated light sources. Use the foil
sample chart in a calibrated light box or under the right desk lamp
light source to compare your gold with the index. If you have any eye
for color at all you will quickly see what category your white gold
falls into. For the GG this is grade school work. If you need to know
exactly what the yellowness index is for your gold you must send it
in to a company that has a Spectrophotometer from Munsell. MJSA can
refer you to these firms.

These standards are voluntary and flexible. If the WGTF is found to
have been too generous or too strict the numbers may shift a small
amount. Every effort was made to include people from retail,
manufacturing, alloy manufacturing and metallurgy. They were put on
the panel to balance the interests. We sampled dozens of white golds
to find the right range of color. For more contact MJSA
and ask about the white gold index.

Daniel Ballard
Copyright 2005