Facetted stones and reflective backings

Jewelry Discussion
1

Hello everybody,

I wonder if anyone has any ideas on improving the sparkle of mounted
facetted transparent stones such as citrine.

I have long admired the brilliant sparkle of Swarovski crystal. I
assume the reflective backing is the reason for this, and perhaps a
major ingredient in their commercial success. It didn’t take me
long to find that this backing is none too adherent to the stone =96
it sometimes comes off when stones are lifted from a wax backing.

In my ignorance, (I know nothing about stone faceting), I thought
that perhaps plating a layer of silver on the back facets (below the
girdle) of a citrine would do the trick. It took me all day to get
the hang of this, and I was disappointed when I found that the
resulting stone had a distinctly dark appearance, with significantly
reduced sparkle.

Is this something to do with the angle of the facets? Would they
need to be different if a reflective backing were plated onto the
stone, and could one expect that suitably angled facets together
with a plated reflective backing would give sparkle to match that of
Swarovski crystal?

Any feedback would be interesting!

Paul Jelley
London

2

The easy answer is to find out what the refractive index of the
swarovski crystal is, and buy well stones close to that. The problem
is most commercial stones are cut for weight so they don’t follow
the necessary angles for best light return. It does indeed have to do
with the angle of the facets. Those angles directly relate to the
materials RI. I don’t know what swarovski’s lead crystal RI is but I
expect it’s higher that 1.56 but I could be wrong.

A well cut stone won’t return any more light from a reflective
backing because the light would/should reflect off the pavilion
facets and back to the viewer. Your stone may have darkend because
you block scattered/random light that might have been entering
around the pavilion.

The angle of the facets, RI, and type of cut will all dictate how
bright a stone is… Avoid fish eye stones.

Craig
www.creativecutgems.com

3

Hi Paul,

Faceted stones can be ‘dead’ looking if they’re not faceted
correctly.

Every stone has a physical characteristic called the ‘Refractive
Index’ (RI). The Ri is different for just about every species of
stone. This is used to determine the "Critical Angle’. The critical
angle is the angle above which the pavilion of the stone shouldn’t
be faceted. If it is, any light striking the crown of the stone will
go out the pavilion & not be reflected. The idea; would be to have
100% of the light hitting the crown to be reflected back out the
crown by the pavilion. In the real world, this isn’t possible, but
reflection rates in the 90% range are possible.

Dave

4 
    I wonder if anyone has any ideas on improving the sparkle of
mounted facetted transparent stones such as citrine.

Yes Paul, there are more permanent changes that can be done to
enhance the scintillation of your faceted gems. Of course I’m very
partial to OMF concave facets. There are gem cutters that specialize
in adding concave facets to already conventionally flat faceted
gems. Here is a link to my home page where you can find a comparison
to the two types of faceting and see how OMF concave facets
compliment flat facets brilliantly. (sorry about the pun :slight_smile:

Here is another link that is well worth the time to paste the link
into the browser and watch down load!!
http://tinyurl.com/crmod

Enjoy!!!

Zane Hoffman, President
Poly-Metric Instruments, Inc.

info@polymetricinc.com

5

I am not an expert by any means, but Swarovski also sells crystal
without the backing and those beads still have that brilliance. I
believe it has something to do with the “lead” in the crystal, and
whatever their process is. They have made a name for themselves
exactly because of the brilliance, and the Czech and Chinese crystal
just isn’t up to standard (yet).

I’m not sure your question has a simple answer. If that were true,
everyone making crystal could do it. Maybe the only quick answer to
your question is to choose great quality in the first place, whether
it be crystal or gem stones. Good luck!

Kerry
CeltCraft Beads & Jewelry, Utah

6 
    I wonder if anyone has any ideas on improving the sparkle of
mounted facetted transparent stones such as citrine.

Hi Paul. better cut proportions will make all the difference you’re
looking for.

    I have long admired the brilliant sparkle of Swarovski
crystal.  I assume the reflective backing is the reason for this,
and perhaps a major ingredient in their commercial success.

Most Swarovski crystal has no reflective backing, apart from
foilback rhinestones. Many of their pieces do have an extremely thin
coating which causes their proprietary effects, such as AB (Aurora
Borealis). Also keep in mind that Swarovski crystal is leaded glass
and not a natural crystal.

    In my ignorance, (I know nothing about stone faceting), I
thought that perhaps plating a layer of silver on the back facets
(below the girdle) of a citrine would do the trick. It took me all
day to get the hang of this, and I was disappointed when I found
that the resulting stone had a distinctly dark appearance, with
significantly reduced sparkle. Is this something to do with the
angle of the facets?

No, it’s more due to the fact that you’ve changed the refractive
index of the citrine quartz. The most recognizable example is with
diamond, which tends to attract grease. When people’s diamond
jewelry becomes dull and lifeless from being constantly worn, it’s
because the dirt and grease from their fingers has changed the
refractive index of the pavilion, thereby widening the critical
angle as well. That means that light is escaping out of the bottom
instead of reflecting and refracting back up through the top, or
crown. You’ve done something similar to your citrine.

    Would they need to be different if a reflective backing were
plated onto the stone, and could one expect that suitably angled
facets together with a plated reflective backing would give sparkle
to match that of Swarovski crystal?

I suppose a person could experiment with facet angles long enough to
create a pleasing effect, but remember that Swarovski uses several
different fumed coatings to get their special look. Foilbacks have
been used to make glass look better for many decades. I suggest you
look for stones with better cut proportions and facet arrangements.
For stones that tend to window, such as rectangular cut citrines,
consider taking a look at concave faceted stones.

James S. Duncan, G.G.
James in SoFl

7

The sparkle of Swarovski crystal has little if anything to do with
the backing and everything to do with the cut and the lead content of
the crystal. I have seen the lead content reported as 30 to 32%.
Swarovski crystal is also cut very carefully for maximum brilliance.
Even their beads which have no backing have superior sparkle. It is
easy to tell the difference between a bracelet made with Czech or
Chinese crystals and one made with Swarovski crystals.

MonaLS - Hayward, CA
Bead*Happy’s Favorites - Treat Yourself to Handmade Jewelry

8

Swarovski crystal is termed as ‘full leaded’ because it has a 32%
lead content. So yes, the lead content is what gives it the sparkle.
Higher than 32% causes the crystal to become grey, and will often
result in explosions during the mixing. Generally ‘cheap’ crystal is
24% lead, but is often passed off as ‘quality’ and will sometimes
even be labeled as fullleaded. But truly quality crystal will always
be 32% ‘fullleaded’ such as Waterford.

Ed in Kokomo

9

Hi Paul,

I understand wanting the look of Swarovski in a gemstone, but the
answers you have received so far confirm my sense that the only way
to get that is to pay top dollar. When I was faced with an
invitation to show my work–and had to make an almost-instant
transition, from student/hobbyist to someone with a line–I chose
to use primarily Swarovksi beads to accent my wirework. I wanted
lots of sparkle, plus consistency of color, quality, and size.
Since I wasn’t willing or able to invest a queen’s ransom,
Swarovski seemed like the only way to go. Now I’m spoiled, and I
suspect that I will be using “simulants” of some kind in my work
for a long time. So… if you can’t afford eye clean stones with
concave facets, have you considered just using Swarovski?

I have thought for a while about how to set the Swarovski “stones,”
and I was hoping that someone on Orchid would post to this thread
about her/his experience with this. If you go into a Swarovski
store, you will see that most of their own “set” jewelry looks like
rhodium- plated crap. I have only seen the work of one jeweler who
sets Swarovski in sterling: Viviana Camquiry, a Latin American
jeweler whose work was in a show at Velvet Da Vinci. The show is
archived, but I don’t think I can grab a URL for the page that
shows her work: you need to go to “shows,” then to “joyas joias,”
then to page 10: http://www.velvetdavinci.com/

I examined these pieces very carefully and am pretty sure she is
using an adhesive to set the “stones,” which I don’t think are foil-
backs. They don’t show much sparkle in the photos, but they
definitely had that Swarovski look “in person.” If anyone has an
idea about exactly what she has done, works in a similar way, knows
the best adhesive to use, etc., I would really appreciate the info.

Lisa Orlando
Aphrodite’s Ornaments

10

Missing the mark.

I saw several replies to why quartz, such as citrine lack some the
spark as other stones have. Several replies got close mentioning RI
or cut. Several factors determine the life a gem shows. Quartz is a
low RI stone. The higher the reflective index (RI) of a gem the
higher it’s ability to reflect light. In simple terms for this
discussion what this means is less light is reflected off the facets
(the cut planes) of a stone. This means that a quarts stone will
never return the light as a higher RI stone such as diamond and will
not “light up” with the same sparkle.

Other factors such as dispersion or the ability to split light into
color such as light entering and leaving a prism will, also enter in
to this. All transparent or translucent stones have some degree.
Diamonds are noted for it. Quartz is not. Another factor is of course
how well a stone is cut to get the most out of its properties.

With quartz stone, citrine, amethyst etc. cut and color are of
utmost importance. As some on the list are unclear as to why two
stones of the same variety, color, shade and grade can look so
different, links are provided to clarify this. All could tell one
stone looks better than some other will, but some have no idea as to
exactly why. Some bargains (which, is why they are so cheap) are
outright optical nightmares.

http://www.theimage.com/faceting/facet5a.htm
http://www.rockhounds.com/rockshop/gem_designs/bow_tie_blues

Although quartz may lack the fire of some gems, it is not so hard to
understand why it has a fan club, for amethyst lovers check this
link.

In short for more flash and dance, I, in my opinion would forget a
reflective backing and choose another stone, not likely to add an
improvement anyway other than perhaps resembling rhinestone, but
quartz, such as good amethyst have their own charms.

11

I think you mean ‘refractive’ index, not ‘reflective’. The RI is the
amount the light will bend when entering a material. The RI is what
determines the Critical Angle of the material. It is the critical
angle that determines the light return. The lower the CA the more
light enters the stone as opposed to be reflected off of it. These
factors also determine the best angles for pavilion and crown facets
to maximize the material.

Another factor that will affect light return is the type of cut.
Barions normally offer a better light return than standard cuts…

Craig
www.creativecutgems.com

12 
I think you mean 'refractive' index, not 'reflective'. The RI is
the amount the light will bend when entering a material. The RI is
what determines the Critical Angle of the material. It is the
critical angle that determines the light return. The lower the CA
the more light enters the stone as opposed to be reflected off of
it. These factors also determine the best angles for pavilion and
crown facets to maximize the material. Another factor that will
affect light return is the type of cut. Barions normally offer a
better light return than standard cuts.

Craig

I see you caught a spelling mistake. (Had my mind on one tract.) How
light is captured and reflected is what gives a gem its sparkle.

The refractive index (RI) is the measure of the amount light is
bent. Determining the critical angle. Above the angle light is
reflected back, below light passes through, resulting in windowing.
This determines how facets should be placed in order to control the
path of light so it will be internally reflected to best effect. The
RI, quote, “also tells how much light will reflect off a boundary”…
(Physic formulas do not help me at all. Not sure they really even
impart understanding in those who can read it.)

On optical performance the RI also determines (all things being
equal) the intensity of light returned to the viewer after entering
the stone and reflecting off the facets (cut planes) and returning
out. Higher RI stones are better at that than lower RI stone. Why a
high RI stone that bends light more also reflects the light back
better (as noted in many places) I have no idea. Only all can see the
result. Which is why white sapphire will be brighter than clear
quartz (rock crystal). Even if both are cut for optimal effect with
best angles, if both were barions of equal clarity and polish etc.
the sapphire will be brighter. That was what I meant to convey.

Of course, usually it is the cut, or lack of that has far more
effect on appearance than other factors. This is the single most
important factor. (Providing it is worth cutting or as said somewhere
about some Ebay material, if light can’t pass through it, it is not
faceting grade, and other remarks.) Even the best material if cut
wrong will have disappointing results. Thai cut gems are notorious
for that, quick and cheap, lack of good polish (usually seen) adds to
that result. The optical performance is often not there and sometimes
more or less completely lacking. Mention has been made to Swarovksi
leaded glass rhinestone. That 30 % lead glass has a higher RI than
quartz (RI, 1.544 -1.553). They are also machine cut to best angles.
I could not tract down the exact RI for Swarovksi cut glass, I
believe it is 1.62. White sapphire was said to be 1.80. When trying
to find the exact Swarovksi glass RI out of curiosity I came across
this. “The CUT of the rhinestone greatly influences its brilliance!
Purchase the rhinestone with cut in mind.” “Do not be deceived by
pricing and think that 3 or 4 times the number of rhinestones applied
to a garment will make the garment outstanding IF you use an
inexpensive rhinestone.”