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Polishing Imperial Jade


#1

I have a piece of Imperial Jade which I would like to recut. I have
the equipment to do the job but haven’t used it for twenty years or
so. I only tried working jade once before and had a great deal of
trouble polishing it. Can anyone out there tell me what compounds to
use for polishing jade. My polishing wheel is leather and I have
been using cerium oxide for the final polish on agate and jasper.

R. Hood


#2

Is it Imperial jadeite? The most important consideration is fine
sanding, finishing almost dry on very well worn 600 grit or finer
abrasive. This brings you to almost a polished state. Others
recommend a progression of diamond - I use SiC. For the final polish
of nephrite I almost always use chrome oxide; for jadeite, linde A
or equivalent sapphire powder.

Jim Small
Small Wonders


#3

Jade is very fibrous. If you raise the fiber with a coarse grit
grinder the finer grinds after that will not get rid of the raised
fibers. No amount of polishing would be of any use. Start with a fine
grind. It will take a bit longer to shape but the end results
are worth it. I polish mine on a leather wheel with cerium oxide.


#4

Hi, I get good results using diamond compond to 50,000. I use a
Genie and after finishing up on the polishing wheel, I go to a flat
lap using the Crystalite fabric pads with the appropriate diamond
grits, starting with 8,000, 14,000 and finally 50,000. I generally
get a mirror finish, although you have to watch for orange peel.
Good luck!

John


#5

R. Hood, Chrome oxide or 50,000 diamond does a nice job. David PS
watch
cross contamination of chrome and cerium as cerium will strip the
polish from jades.


#6

Richard,

    Jade is very fibrous. If you raise the fiber with a coarse
grit..... 

I assume you are referring to nephrite jade? Jadite is
cryptocrystaline in structure and tends to “orange peel” vs “slake”.
Also, when dealing with nephrite, it depends on how it was slabbed.
If it is cross grain, the slaking is not such an issue though the
stone tends to loose some of its toughness. If cut with the grain it
can slake but will be tougher. The final polish, in either case,
should be about the same if it is properly prepared before polishing.

When preparing either jadite or nephrite, it is important to go
light on the coarse wheel to prevent sub-surface bruising/cracking.
I do most of my shaping on a 600G wheel then smooth on a 325. Then,
and this is important, use well worn 240 to 280 si paper. Start out
wet but let the wheel dry from friction. Use moderate pressure until
the stone heats up until the dop wax nearly melts. Let it cool a bit
and do it again. THEN, use the worn 400 or 600 si paper and again,
start out wet and let it dry. Polish on soft leather backed with
rubber with chrome oxide (which is very messy like iron ox) or
Linde/Raybright A. If jadite, smoothing and polishing can be in any
direction. If nephrite, smooth cross grain then finish polishing
along the grain briefly.

Cheers from Don at The Charles Belle Studio in SOFL where we are
watching the first true tropical storm of the season and where simple
elegance IS fine jewelry! @coralnut1


#7
    I have a piece of Imperial Jade which I would like to recut. I
have the equipment to do the job but haven't used it for twenty
years or so. I only tried working jade once before and had a great
deal of trouble polishing it. Can anyone out there tell me what
compounds to use for polishing jade. My polishing wheel is leather
and I have been using cerium oxide for the final polish on agate
and jasper. 

Jade is one of the hardest, and easiest stones to get a polish on.
I had an Asian customer bring in a very nice stone and ask me to
re-polish it. She informed me that only cutters in Hong Kong could
polish Jade. I almost proved her right that time but have since
found it is not a big deal

I found that if you try to polish in a poorly sanded stone, it will
drive you nuts. The key to getting that mirror finish is to sand the
stone well. For a worn stone, you will need to sand out all of the
scratches and nicks. This of course means removing it from the
mounting and mount it on a dop. Once you have the stone sanded down
to at least a 1200 grit finish, with no scratches left from the
previous step, wet your leather lap. Make sure it is very wet, all
the way through. Now give is a good charge of Linde A. Rub it in
with your finger until you have a good coat over the surface of the
lap. Make sure it is not clumped up, but a nice even spread. You
should not feel any lumps Now spin up the lap, speed wont’ hurt
here, I use a Genie and it spins at 1735 RPM or so. Before you put
the stone to the lap, give the lap a spritz with a spray bottle and
then using a hard pressure push in the stone and twist it at the
same time, removing it after about 1.5 to 2 seconds. This generates
a lot of heat at the surface and helps generate the polish. Repeat
this step, checking every couple time by touching the stone to your
cheek to make sure you are not softening the dop wax. I keep a
container of water to dip the stone in after each swipe. You don’t
want to generate enough heat to soften the wax, but almost. The key
here is the swipe and turn, Don’t linger at any spot, and don’t
polish to long or an orange peel will develop. You want to get in
quick, push hard, and get out quick. It should take less than two
minutes total time to produce a top finish on a well sanded stone.
Don’t let the leather dry out, but is should be almost dry. Right
at the point that it wants to pull the stone out of your hand.

I have tried different compounds, cerium oxide, chrome oxide, tin
oxide, and diamond grits of 50K and 100K. Nothing produces the
great finish like Linde A and an almost dry leather lap along with a
heavy hand.

Don


#8

I have had excellent results for many years using the diamond pastes
on jade I usually wind up polishing with 14000 mesh As always, NO
shortcuts I prepolish with 3000, then 8000, then 14000 I’ve tried
50000, but i don’t see any difference For me, leather and cerium
lead to orange peel Incidentally, I use a Polypad on a flat disc
backed by a layer of inner tube, and I use plenty of diamond paste

Wayne Emery