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Polishing black coral


#1

I would like to mine the collective knowledge of this group for
on polishing black coral. I have some lovely branches
with a natural matte surface and would like to achieve the high gloss
I’ve seen on finished pieces. I understand that black coral is
proteinaceous rather than a carbonate like red and pink and must be
kept cool, but what polishing compound or techniques are best?

Barbara W. Smigel, PhD.
Colored Stone Graduate, GIA
Artistic Colored Stones
http://www.acstones.com


#2

Barbara, There are a number of polishes that will give good shine to
black coral. But first, you need to smooth it through a series of
processes including using coarse and fine files, then at least two
grits of sand paper 100 and 220 grit followed by Scotch pads to give
it a satin like finish. Then use a cotton muslin stitched buff and
load it with ZAM. I like a high speed-3400 but slower speeds are
ok…they just take a bit longer. Polish the coral all over
horizontal to the wheel and then finish it parallel to the wheel.
Black emery, Fabuluster, white diamond, and several other polishes
will work but none as well as ZAM…regardless if its shallow water
Gorgonian or deep water Antipatharian.

You are correct, it should not be made too hot or the surface will
’burn’ into a light brown and that is a devil to get rid of. But,
with the muslin buff, it is difficult to get it too hot unless you
use lots of pressure and hold it in one spot too long…keep it
moving…keep it moving.

Enjoy and cheers from Don at The Charles Belle Studio in SOFL where
simple elegance IS fine jewelry. @coralnut.


#3

Hi Barbara, I’ve got some south Pacific black coral that I inherited
from a relative who brought it back during W.W.II. This is apparently
a different species than what is found in the Caribbean or washed up
on Florida shores. I have used tripoli on a buff to “sand” through
the outer skin and red rouge on a buff to polish. Works beautifully,
and reveals orange metallic flecks.

Hope this helps,

Dave
Dave Sebaste
Sebaste Studio and
Carolina Artisans’ Gallery
Charlotte, NC (USA)
dave@sebaste.com


#4
I have some lovely branches with a natural matte surface and would
like to achieve the high gloss I've seen on finished pieces. 

Greetings Barbara In the past I have experimented in polishing black
coral and find that I get a very high gloss polish by using the
normal polishing and emerying techniques used for gold and silver. In
my case I use the various grades of emery followed by tripoli on a
stitched mop and rouge on a calico mop, this takes time and patience
but works well. Don’t clean in water after as it may remove the
polish and lift the grain of the coral. Green rouge could be a good
alternative to red. Wipe the piece clean after polishing, there
should be very little compound left on the coral anyway. Getting a
good polish on cross section grain can be a bit more difficult but a
reasonable polish is possible.

I must add to this that the coral I polished was large pieces, one
large enough to make a walking stick out of. For finer branches it
may be wise to go steady until you get the hang of it. Thicker
branches also make the most beautiful graver handles when shaped
properly. Inlayed with mother of pearl and with silver ferrules, they
catch peoples eye when your using them or just having them on your
bench.

Happy experimenting
William Russell in sunny Cairns Queensland Australia


#5
    on polishing black coral.  I have some lovely
branches with a natural matte surface and would like to achieve the
high gloss I've seen on finished pieces. 

Barbara, You can sand the matt surface off with sandpaper, ending
with 600 grit paper. Then polish with yellow rouge using a muslin
buff. If you need to get into nooks and crannies, use rouge with
soft MK bristle brushes on your flex shaft.

If you want to speed things up, instead of sandpaper, you can use
bobbing compound on buffs and/or brushes to get rid of the matt,
shark skin-like surface. Clean off the bobbing compound residue and
then finish off with the yellow rouge.

How large are your branches? If they have very thin, tiny branch
terminations, it will be dangerous to try polishing them. The
branches may catch and break even if you polish by flexshaft. What
are you planning to do with them? If you just want mounted
specimens, leave them natural. If you’re talking about “y” shaped
pieces or other such small sections for jewelry use, you can polish
them quite easily so long as they are sturdy enough.

HTH,
Donna


#6

Hi Barbara, I’ve polished black coral on my Rouge wheel and it came
out beautifully. In the rougher areas you can us tripoli, wash and
then rouge. Don’t get the coral too hot on the tripoli wheel or the
stench of burnt hair will prevail! – Lisa Hawthorne @Lisa_Hawthorne_and_S


#7

I have good results using 600 sand paper and then going to zam but
you should allways wear a mask as the dust is toxic and can cause
lung damage . I work with it out side as well