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Opal setting philosophy

Hi Folks,

And you thought we’d already beaten the subject of opals to death
this year! Not quite yet! :slight_smile:

I have an internal debate raging, and I’d like to see what kind of
thoughts you people have on it. I guess this applies more to
transparent and translucent opals (crystal, semi-crystal, etc.), than
to opaque ones. I’ve heard of goldsmiths blackening the inside of a
setting with a Sharpie marker in order to enhance the play of color.
I have actually inserted black paper beneath the stone in the past.
My thinking is that it might be better to polish the inside of the
setting to be more reflective and keep the available light in play
longer. Of course, it could be argued that this will alter the
perception of the body color of the stone, too. My
none-too-scientific testing on the subject was inconclusive.

To further complicate things, I’ll often use an open back setting
for an opal, for two reasons. One, to illustrate to the customer that
it is a sold gem opal (as opposed to boulder, triplet, etc.) and two,
to save on gold. Sometimes I’ll pierce something in the back of a
closed back setting to reveal the back of the stone in an artistic
way. I’m really questioning whether this is detrimental to exhibiting
the stone to its best advantage… although it is kind of cool to
glimpse the piercing through the stone on a couple of them.
Especially with an open back pendant, I suspect what it is worn on
could have a bearing on how the stone appears.

Anyone care to share their ideas on this matter? Does anyone else
torture themselves over silly little things like this? Thanks,
Hanuman, for giving me a place to get some therapy for my fixation!

All the best,

Dave Sebaste
Sebaste Studio and
Carolina Artisans’ Gallery
Charlotte, NC (USA)

I recently did a pendant and earrings in white gold for a customer’s
white opals she’d gotten in Australia. The pendant I did with leafy
vines minimally enclosing the stone- the back was open. Lovely stone,
looked great. But the earrings I bezel set, with the vines along the
outside of the bezel. Closed back with post. These stones lost all
their fire in the bezels against the white gold. But when I darkened
the inside of the bezel, they really popped.

My philosophy? Whatever looks best.

Janet Kofoed

Actually, I think mounting a translucent opal with a highly polished
back may turn out to hide the fire rather than accentuating it,
unless it is a contra luz. It stands to reason, as a polished back
has exactly the opposite effect of a black backing. It shouldn’t be
hard to test, though; take your translucent opal, place it on a
mirror with good illumination, and then place the same opal on a
black background with the same illumination. Which looks better?

On a side note, and totally off-topic, I have switched my operating
system to Linux Mandrake 8.2. What a fantastic OS! I will never go
back to MS Windows. If any of you want info on this, please contact
me off-list.

Lee Einer

 My thinking is that it might be better to polish the inside of
the setting to be more reflective and keep the available light in
play longer. 

Dave, the nature of opal, other than contra luse, is that reflected
light produces color while transmitted light kills the color. This
is the reason that a black backing is used on opals, it reduces if
not eliminates the transmitted light. Using a polished backing will
increase the transmitted light to the point that only a very bright
opal, a 4.5 to 5+ would show color, and even that would be reduced
because of the transmitted light.

In case anyone is not sure what I mean by Transmitted vs Reflected
light, a window is an example of transmitted light, it is fully
transparent. A mirror is a good example of reflected light, you
can’t see through it, but rather the light comes from the viewers
side. These are extreme examples. In faceted stones, the desire is
for transmitted light that is reflected by the pavilion. The light
picks up the color of the stone and the greater amount of stone the
light passes through, the greater amount of color imparted. If you
were to treat an opal the same way, the fire would all but
disappear. This raises some interesting problems for those of us
who facet opal. We need to strike a balance between getting good
reflected light and still maintain a transmitted light return. A
contra luse opal solves this problem, as it’s color is from
transmitted light.

If you think an opal would look better with a polished backing, you
can test it by cutting a hole almost as big as the opal in dark
paper. Lay the opal on a mirror, and place the paper over it so the
opal is showing through the paper. Now with normal viewing light,
appraise the color. Now take the opal and apply black fingernail
polish to the back of it and appraise the color again. You will
almost always find that the blackened back produces the best color.

There are ways to blacken the back of opals that are more permanent.
The black marking pen is a temporary treatment as well as the black
fingernail polish. Both are attacked by moisture and movement. The
fingernail polish is more permanent than the marking pen. A coating
of blackened epoxy it the best. Another trick is to use black RTV
silicone and line the bottom of the bezel. Let it dry before
setting the stone. This is tricky as you need to get an almost
smooth surface as well as getting the depth correct, all without
spilling over to the outside of the bezel. It is not a technique I
would recommend, however I have repaired a couple designer pieces
that had the opals set in this manor, and it was a very effective
way of blackening the back.

If you use the black epoxy method, you can set the stone while the
epoxy is wet, but you must be very careful not to make contact
between the back of the opal and the metal as you will get a spot of
transmitted light through that distracts from the appearance of the
stone. This is a common problem when doing inlay work.

Don Rogers

    And you thought we'd already beaten the subject of opals to
death this year! Not quite yet!  :)  I've heard of goldsmiths
blackening the inside of a setting with a Sharpie marker in order
to enhance the play of color. I have actually inserted black paper
beneath the stone in the past. 

Dave: No solid answers follow, just a few thoughts…

I’ve been wondering about this as well. I have noticed that some
(especially white) opals seem to become much less dramatic as I
finish the back of the stone. I am torn between two conclusions: 1)
the polished back lets more light escape out the back, or 2) the
polished back lets more light in to reach the face thus decreasing
the relative brightness of the refracted light.

In “Opal Cutting Made Easy”, Paul B. Downing, Ph.D. recommends
painting the back of triplets. But he makes no mention of this
technique for other opals. I’ve often wondered if it would work for
other opals, at least increase the contrast of the visible
play-of-color, but haven’t gotten around to trying it.

If you like the effect from black paper, I’d suggest black
paper-micarta, available from knife making suppliers. It will stand
up to wetting, soaking, etc and can provide a bit of cushioning.

The “foiling” thread earlier this year inspired me to wonder whether
it might be better to increase the amount of light coming back from
the stone. But I’m not sure about the physics of this, given the
nature of the defraction that causes the play-of-color.

Wonder what others will have to say…

Michael Conlin
President, Conlin & Associates

Dave, Opals are an addiction. After many years of opalholism I
became cured over a very expensive lesson from opal. The lesson
learned is do not try to make opal into what it is not. I was one
who would do anything I could think of to make the stone better and
more saleable. Now my philosophy is to display the stone in its best
manner. I detest doublets and triplets especially when they are
colored, dyed, or sugared to change them and create an illusion of
value that does not exist. Another jeweler I know came up with a
novel approach to clear body opals. He designed a solid back to the
bezel which he pierced in different designs. He used mostly
astrological designs. Backing plate that was not cut away was
oxidized black or polished. In this manner the customer could
readily see that the stones body color was translucent. Artistic
impression was conserved with the mounting.

Gerry Galarneau

Hi everyone, My own approach is that when an opal has play of colour
(fire), as a general rule, and with the exception of contra luz opal,
the more transparent the stone tends to be the more it improves set
in a black backing.

Hans Durstling
Moncton, Canada

Greetings Dave, Re. your opal query: Basically, it’s “yes” to
everything you mentioned. It all depends on the stone and what works
best with it - and safely. The play of color in
transparent/translucent opals (so called white opals) can usually be
enhanced if placed on either a black, or a white background material.
I’ve set opals which looked good either way and it was a subjective
choice as to which was preferable. I’ve set many others which looked
best on black primarily because it made the play of colors far more

If the stone in question has a yellowish tinge, then a white
background often shows that up worse than a black one. However, the
black background can cause the opal to show as grey which is usually
not attractive. When faced with this dilemma I usually try laying
the stone on the two respective colors (pieces of paper) at the bench
and see which appears best. In the case of a piece to order, you
might want to involve the customer in the decision as well.

Polishing the interior of the bezel - or matting it - usually tends
to feed the color of the metal into the stone. With white metals
this is not so much of a problem, but with gold I don’t like the look

  • makes the stone too yellow and mutes the color play.

As for what to use behind the stone I have a couple of suggestions.
I have pulled many opals set by jewelers unkown who used paper, or
sawdust, or who knows what, to either pad and/or enhance the color
of the stone. Anytime these came out of rings what was behind the
stone was nasty, having taken on moisture resulting in the
decomposition of the padding material.

My first choice for white is to use the file dust from a piece of
white delrin (the fellow who taught me, used sawdust from the bench
pin). The delrin makes a great cushion material, provides the
necessary white background, and is impervious to moisture. I have
used the black delrin as well, but when it is filed the resulting
filings are a definite gray, and not black. Only certain stones have
looked good with it.

I have also used very successfully both white and black silicon
rubber. If you don’t want to literally glue the stone in with it you
have to find a way to place the rubber in the bezel smoothly and
allow it to set befoe setting your stone. You might try a dapping
punch or chasing tool of the appropriate size and shape. Using a
little water on the tool end helps to keep it from sticking to the
rubber itself.

I recently set an incredibly fractured opal a customer brought me by
making a very close fitting heavy bezel and then using the silicone
rubber to “set” the stone via the glue action. This meant no
mechanical force on the stone at all, plus the added stability of the
stone being laminated to the bezel with rubber.

One can always purchase little bottles of black and white enamel
from a hobby store and literally paint the back of the stone as well.
Then you can use whatever you want for the padding material without
fear of it’s affect on the color.

As for the open backs. While some stones - and finished pieces -
can be very beautifully set in this manner it does have the potential
drawbacks you mentioned, besides the increased danger to the stone in
the setting process. Most opals are not that perfectly shaped on
the back and getting a well fit seat around the edge is tough, which
makes more likely a break if stone becomes bound between the force
laying down the bezel and a minute high spot on the seat.

Except for the very brave, the latter requires the use of a thin
bezel material which I am not personally fond of. Using the heavy
bezels I do requires some cushion under the stone hence my preference
for a backing material.

Thanks for wading through this,

Les Brown

It’s funny, I find the opposite in a sense with opal. The dark
background generally works best with clearer material, depending on
the brilliance of the fire. I think shiny metal kills the fire
because of the complicated way opal uses light. The mirror finish
on metal often cancels the internal integrity of the fire.

On white base, the darker background frequently does not work or
makes little difference.


I agree with you Derek. A bright and shiny surface behind jelly or
xtal opals really washes out the fire. So too leaving the back open
on such opals tends to defuse the fire and you loose the brilliant
flashes (with some exceptions though). White, gray, black, or other
colored opals with opaque potch will not be affected by an open back
but then there is no reason to polish the bezel base either. I often
finish the back as well as the crown on such opals and then set them
open in front and back so both sides can be enjoyed. Guess personal
preference comes in here. Cheers from Don at The Charles Belle
Studio in SOFL where simple elegance IS fine jewelry!

Hi all , I have a couple of questions , what is a contra luz opal ?
Next , a few years ago I made a broach - silver with an orange
Mexican fire Opal in an open setting - I wanted the colour to shine
on the background . It looked good , but the fire - subtle to start
with - doesn’t stand out . I wonder if a darkened setting , as a few
people have mentioned lately , would have been better ? Any help for
next time would be appreciated . Philip Wells

  Hi all , I have a couple of questions , what is a contra luz
opal ? 

Contra Luz is Spanish for against the light. It requires light
passing through the stone to exhibit it best color. It is usually a
yellow, orange,or sometimes clear base color, and is mostly Mexican
in origin, however Oregon produces some nice material also.