How to Collect and Process Black Coral

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How to Collect and Process Black Coral
By Donald C. Dietz
(An excerpt from his August 2000 Lapidary Journal article)

Florida’s Gorgonian black coral species most suitable for making
jewelry are the sea bush (pseudoplexaura parosa [porous false
plexaura]), knobby or spiny candelabrum (eunicea species), tan bushy
coral (plexaura flexuosa), common bushy coral (plexaura homomalla),
and Guadeloupe sea blade ( pterogorgia guadalupensis). Other species
such as sea fans, sea rods, sea plumes, sea feathers and deadman’s
fingers, are also found but are either not black when dried or
otherwise not useful for jewelry purposes. A few words are in order
regarding sea feathers and sea plumes, often grouped with “black
coral”. These varieties are not easy to clean due to the tough spines
running the length of the long graceful stems. They can be smoothed,
with some effort, and take a beautiful polish which shows them to be
dark brown to nearly black in cross section but very dark brown with
lighter brown twisted lateral bundles in the axial view. A cross
section of a large diameter limb can make an excellent cabochon but I
have found no easy method to bend or shape the brittle (and tough)
stems. Some use may be found for straight polished segments. I have
also found that the main stems from both of these corals and deadman’s
fingers coral can be used to make beautiful beads.

Additionally, the true “sea fans” (gorgonia ventalina and gorgonia
flabellum) as found in South Florida are rare and highly protected and
usually either too small or too fragile for making jewelry, though
they may make excellent specimens.

Often black coral is freshly blown onto South Florida’s beaches with
little or no damage and with the calcareous outer shell (spicules)
still clinging to the limbs. Black coral can be found caught in the
rocks of breakwaters, tangled with seaweed or fishing lines at the
water line or just lying on the beach. A sharp eye can often spot the
top two to three inches of a coral branch sticking out of the sand.
The reward may be a large buried branch or tree.

When found wet on the beach, the surface of black coral, sans the
spicules, will appear muddy brown. But do not be misled because as it
dries the layers compact, actually shrinking by a quarter or more in
size and turn jet black. Actually, black coral isn’t black. It is a
bit like “black” nephrite jade; i.e., a piece of thin nephrite held up
to a light looks green or brown; whereas the coral appears brownish
red.

Unfortunately, around the Port Everglades inlet near Ft.Lauderdale,
coral is often tainted with oil blobs from ships using the inlet. The
sticky oil can be removed with Gunk used for cleaning engines; just
spray it on, wait 10 minutes and hose it off. Occasionally a coral
tree with the spicules still attached may be found saturated with
black oil. Wait until it dries and then break off the outer layer by
pounding it gently with a wooden mallet or blunt object such as the
edge of a board then wash with Gunk.

When collecting fresh black coral, you may notice a strong
fishy odor due to saltwater saturating the coral skeleton and any
remaining calcareous layer, or seaweed clinging to the branches.
Clean the coral of debris before leaving the beach and rinse it with
fresh water at a beach shower before putting it in your car. Rinse
again at home with fresh water and dry it in the afternoon sun. By
then the smell will be sufficiently lessened that it can be taken
indoors to dry completely for two to three weeks.

It is important to pick up the coral as soon as possible after it is
deposited on the beach because the hot sand “cooks” it and makes it
brittle. Also the coral will begin to deteriorate and display brown
“woody” spots. Eventually the entire tree will turn brown. This are
difficult to remove and can result in loss of valuable material,
though at times, small spots create lovely patterns that may be
incorporated into a jewelry design. Remember, the larger and blacker
the coral, the more beautiful it is, and the easier it is to clean and
work into various designs.

JEWELRY CHARACTERISTICS

The physical properties of black coral generally support its
usefulness as a jewelry material, but some also work against it. One
attribute is its workability with the simplest of tools. It can be
trimmed, smoothed and polished much in the same manner as a fine hard
wood. It is ultra-light and when polished to a high shine feels and
looks much like black plastic. Small or thin pieces may be quite
brittle but thick material is quite durable. The polish must be
protected from abrasion or it will become dull. It chars easily when
subjected to an open flame and the surface will “burn” and turn light
brown due to friction when polished on a felt wheel. Thin wet limbs
are easily bent or formed into many shapes and even tied into knots.
When dry, it is stiff and hard and takes an excellent polish, however,
after being formed to a particular shape it must be protected from
water, which it will absorb making it soft and pliable again. Thus,
beautiful hoop earrings could at best become horseshoe-shaped, or at
worst a long shapeless stick.

I have collected bits and pieces of black coral for many years and
have seen it fashioned as jewelry in parts of Japan and on Hawaii
where it is revered as a gift of nature by native Hawaiians. But,
while practicing the art of lapidary and gold and silversmithing for
over 25 years, I never learned how to work with it until the article
“Black Coral Pendant” by June Culp Zeitner appeared in the Jewelry
Journal of the March 1996 Lapidary Journal. This article spurred my
interest and after researching Lapidary Journal articles dating from
the 1960’s, and various other references, I was hooked. Now I
actively search the beaches hoping to find that one gigantic black
coral tree. Meanwhile, I will settle for any little piece that looks
like I can get an earring or perhaps a small pendant out of it.

WORKING WITH BLACK CORAL

Anyone with rudimentary lapidary, woodworking, or crafting experience
can learn to work with black coral. The necessary tools will vary
with ones’ talents and preference but will generally consist of small
saws, various files, knives, several grades of sandpaper, polish
compounds, a polishing motor and buffs, drills and various wheels, and
other items that can be used to smooth, shape, bend and polish.

First look at the raw dry coral with its twisted and gnarled limbs,
uneven surfaces, and tree like appearance for a hint of something
unusual. Look for a particularly shaped crotch formed where one limb
grows from another, or several off-shoots that might form a geometric
(or ungeometric) design. Is a branch long and well shaped with few or
no offshoots? Is it about the same size from where it leaves the main
trunk to its end? Are the trunks and branches round, thick, and
smooth or flattened with irregularities? If you do not have a
specific design in mind these shapes may influence what you can or
should do. If you have something specific to make, find the material
that will fit your plan. Plan how to cut the tree keeping the pieces
you consider usable and discarding the rest, though I find it
difficult to throw any of it away unless a piece is badly
deteriorated, too thin or heavily infested with disease. The latter
is indicated by hollows or bubbles in the surface of the trunk and is
filled with a form of calcium carbonate. Take a good look at the ends
of the long branches. If hollow, they cannot be easily bent or shaped
without kinking except in long graceful curves. The best coral is
solid except for a tiny core usually about the diameter of a pinpoint.
Look at the main trunk and limbs, which should also be solid and jet-
black. If there are woody or calcareous areas growing into or under
the surface, or hollows, you must decide to remove them or keep them
as they are.

Cut and trim the coral into pieces that are the size or shape
necessary to do a project. Use a hacksaw, jewelers saw, various cut
off blades in a Dremel or Foredom tool, a small scroll saw or whatever
you find convenient to cut through a piece of dry coral up to an inch
thick. Small limbs can be snipped with side cutters but this leaves a
ragged stub that must be filed down. The goal is cut the coral tree
into pieces of varying size and shape that can be smoothed, formed,
and polished. I find a 360-degree scroll saw blade very useful for
getting into tight areas. Fine cutting can be done with a jeweler's
blade or small back cut saw. Motorized cut-off blades are quick and
leave a neat cut but cause a lot of dust and, if used at high speed,
can burn the coral.

When using any motorized blade or tool, wear a dust filter mask and
eye protection.
The make up of gorgonius is protein with high concentrations of iodine
and bromine but there is no telling what other chemicals or minerals
are present.
In any event, I doubt if the dust is good for your health and some
people are allergic to it.

I have read articles that discuss the sanding or “grinding” of black
coral when it is wet. I have tried it and, for me at least, it does
not work. It appears that the wet process may be limited to the
Antipatharian or deep-water variety of black coral that comes mostly
from Hawaii but can also be found in some parts of the Caribbean. It
is slightly harder and more stone like than the shallow water
Gorgonian found in Florida waters. Other than soaking the coral in
preparation for bending or forming of branches, the following steps
are all performed on bone dry coral.

Remove nubs along the limbs by filing or sanding before generally
smoothing any damaged areas. I use a heavy-duty half round wax file
to remove large surface blemishes followed by finer files to smooth
and shape the surface. Try to retain the natural curves or surface
grain, but otherwise the surface must be even and smooth enough to get
at it with a buffing wheel. Sometimes the grain is so clear and nicely
formed it is wise not to polish it. Blasting with sand or other
abrasives can strengthen this natural look and produce a beautiful
matte finish. The initial smoothing is a difficult step because it
requires considerable hand strength to hold the coral steady while
filing or cutting. Also, you may find coral difficult to smooth when
filing in one direction due to growth grain, which may change several
times throughout the length of a branch. Merely change the direction
of your smoothing stroke to accommodate the grain. There is no one
file or method that is best at this stage. Large pieces may be easier
to manipulate but might require more filing or cutting. Small or thin
pieces are more difficult to hold but may be naturally smooth. The
process is much like cutting a stone--each succeeding step shapes and
smoothes the material so that scratch lines from the previous step are
removed. As you smooth the surface, blemishes may appear. Especially
troublesome are the holes that result from removing off-shoot
branches. Sometimes the core-hole extends into the middle of the
mother branch, while other times it is very shallow. Nothing can be
done about the former except to cut them out, while the latter can be
filed out resulting in a longer more useful stem.

After filing, I have found various types of nail files to be useful.
These can be purchased in most department or drug stores. I normally
start with one that is an inch wide by 8 inches long with180- or 240-
grit silicon carbide on a hard but flexible board. This does an
excellent job on larger pieces and easily takes out the file marks.
Some minor shaping can also be done but the general shape should
already have been determined by cutting/filing. Next I use a nail
file that has a 280-grit on one side and 320- or 400-grit on the other
with a foam board in the middle. This board is softer and follows the
rounded contours well. It also gives a nearly ready to polish
surface. Hard to get places can be cleaned and smoothed using various
plastic scouring/sanding pads. These are excellent for getting into
crotches and between limbs. Final sanding can be done with worn 400-
or 600-grit silicon carbide paper. These final smoothing steps are
important because they take the work out of polishing.

Any remaining scratches must either be re-smoothed or polished away
using considerable pressure against the polishing wheel, which could
result in overheating the surface and burning the coral. When this
occurs, it is nearly impossible to remove the resulting brown area.
Brown speckles (caused by deterioration) that remain after final
sanding can sometimes be removed by scraping across the surface with a
very sharp hobby knife or a razor blade. This removes material more
quickly than filing or sanding, and leaves the surface relatively
smooth. With practice, you can control exactly where and how much
material is removed.

I have found it best to pre-polish all pieces before forming, bending,
or making the final piece of jewelry. Forming and bending may result
in curves or corners that are difficult to access for smoothing and
polishing. Even after soaking and forming the coral, about 80 to 90%
of the pre-polish will remain. If you intend to carve the piece, it
is wise to pre-polish as it can reveal imperfections or an irregular
shape that could affect your plans. At this stage these can often be
corrected.

ZAM is an excellent overall polish for black coral. Fabuluster, black
emery, rouge, and some others do a good pre-polish but finishing with
ZAM seems to give the highest luster. Whatever polish you use, use it
on a multi-layered, one inch wide sewn muslin cotton buffing wheel.
Do not use felt; the high surface temperature will quickly burn your
coral. A 3450-RPM motor is recommended but a 1725-RPM or just about
any other motor can be used in a pinch. If the buffing wheel becomes
too hard cut the stitches to soften it. This will ensure the
polishing compound penetrates the wheel and gives good polishing
action. Use smaller 1-1/2” to 2” inch diameter cotton wheels on your
Dremel or Foredom tool for the hard to get places but be careful as
these wheels may “burn” the surface or grab the piece from your hand.

There are some tricks to getting a good polish on black coral. Keep
the wheel well loaded with polish. Initially, keep the piece
horizontal to the wheel and support it with your fingers or a wood
block. Run it back and forth the length of the coral branch, using
moderate to heavy pressure. This will quickly highlight any remaining
filing, sanding marks or irregularities. Under the proper speed,
pressure and polishing medium the outer layers of protein melt and
flow. Thus, minor scratches or surface blemishes may polish out.
Otherwise, correct them by additional sanding before continuing.
After you are satisfied all such marks are removed and the coral has
an even shiny appearance, run the coral lengthwise (vertically) up and
down the wheel parallel to the grain using light pressure. The
resulting shine will be well worth all the effort you have put into
preparing your coral.

FORMING AND SHAPING

Shaping black coral is an experience in itself. Thick solid pieces
can be carved or sanded to any shape. Keep in mind the center (or
slightly off-center) core can suddenly appear right in the middle of
your otherwise beautifully carved humped-back whale. Be aware also of
any hollows or other blemishes previously identified or suspected.
Start with easy shapes; an easy one to make looks like a baseball
bat. You may also incorporate any original curve into the new form.
More sophisticated bends or curves can be attained by soaking the
polished black coral branch in water (hot water does it faster; cold a
bit slower but just as effective) and forming it around a dowel, or
inside various items such as a jar lid or a can. While learning to
work with black coral, select only solid pieces, as you will find the
hollow ones difficult to work with. As you gain experience, you will
find the hollow limbs useful in some forms as well. Following are some
examples to obtain specific shapes.

To make large hoops, place two wet branches 4 to 10mm in diameter
inside a jar or can with a 2 inch inside diameter. If you want the
ends to meet when dry, overlap them by about 1/2 inch. To create a
hoop with a 1/4 to 1/2 inch gap make the ends meet when wet; they will
separate as they dry. If the branch has some irregularities in its
length, wait until it is just about dry, remove it from the jar/can
and place a flat weight of about 4 to 8 ounces on it for 12 hours.
This will insure it is a flat round hoop.

To make several other shapes, wrap a wet 4 to 6mm x 6 inch branch
around a 1/2 to 3/4 inch wooden dowel. Tape, nail, or pin it at the
ends to keep it from unwinding. Let it dry for at least 24 hours and
slide it off of the dowel. Cut the tightly wound coil lengthwise to
make small hoops (as in making jump rings). Dampen the hoops slightly
and dry under a 4 to 8 oz weight to bring the ends even.

To stretch the tightly wound coral into a corkscrew, slightly dampen
it, pull the ends apart until it is the shape you desire and keep it
that way for another 24 hours. If you attempt to stretch the
corkscrew without dampening, it will probably snap!

A simple crossed loop can be made by bending a wet branch around a 1/4
inch dowel and pinning the coral at the point where they cross. Let
it dry for 24 hours.
Many other shapes can be obtained by the use of clips, dowels, jars,
cans, boards with pins or holes in them or special “jigs” designed to
hold the coral in a specific position until it has completely dried.
If a shape does not quite conform to your specifications, dampen it
and try again.

Use steam from a tea kettle to quickly form or correct bends and
curves. A propane torch, alcohol lamp, “lil torch”, or a 1500W hair
dryer can also be used to gently heat the coral for forming. Heat
should be used only as one becomes more experienced as the coral can
easily burn or become misshapen. The secret is to not be in a hurry.
Give the coral plenty of time to set-up and dry or cool otherwise it
may become warped. When wet, thin branches of solid coral can even be
tied into various kinds of attractive knots, provided they are not
pulled too tight too quickly.

FINAL WORK

After the black coral has been shaped, it can be drilled with a
variety of twist drills or points to fit sterling silver or gold
findings. Eye pins or other findings can be glued into the coral with
epoxy. The ends of hoop ear rings or bracelets can be finished by
making a small bezel cup, adding a jump ring and attaching the cup to
the coral with epoxy. There is almost no end to the variety of designs
for black coral. It looks just as beautiful with gold or silver; add
pearls, red or pink coral beads, or gemstones to achieve your concept.
Stones such as turquoise or opal are beautiful when inlayed and framed
by the jet black and shiny coral.