What I really need is some suggestion on how to get
about polishing jade - jadeite/nephrite and how to
grade or to distinguish between natural and treated.
G’day Chris; The main problem with polishing nephrite jade is
that it is not a homogeneous material; that is, there are soft
and hard spots throughout a piece. The trick is to reduce the
entire surface of the jade to the same level. So to begin with,
having shaped the piece to your requirements you then begin
sanding. I start with wet-and-dry papers, wet at 230 grit, then
move to approx 300 wet, then 300 dry - the water makes a big
difference. Next I use 400 dry, all the above papers on half-inch
thick by 8 inch dia wooden discs running at about 800rpm. The
discs have a thin (1/8") sheet of medium foam rubber with the
papers spray-cemented on that. It is essential that at this
stage you use the 400 paper dry, for water will help the abrasive
cut into the soft places, which you don’t want. You will get a
nice pre-polish with the 400 grit, and you can move to 600, but I
find it unnecessary. I go straight from 400 dry to an 8" disc
faced with fairly thick but soft leather, nap side out, and paint
this thoroughly with a slurry of tin oxide and water (I use an
old shaving brush and keep the slurry in a tightly lidded plastic
container.) You will quickly see a polish beginning, but at that
stage you must apply plenty of pressure on the work and suddenly
you will feel a drag - and only then will the brilliant polish be
obtained, for what you are achieving is not a micro abrasion but
a kind of molecular flow - a smoothing, flowing movement of the
first few layers of surface molecules, rather than a removal of
the microscopic high points. However, having said all that, if
your workpiece has many indentations, tight inside curves,
piercings, etc, you may have to use 50,000 diamond paste on
home-made polishing sticks, etc, or even bamboo skewers as used
for shish-kebab to get into these places. But use the papers and
particularly the tin oxide slurry as I have described and you
won’t be disapointed with the brilliance of the polish.
I have never come across anyone who has any experience of
treated jade - I don’t know how or even why anyone would want to
treat the beautiful natural stone. The only treatment used in
the Jade Factories on the West Coast of the South Island of New
Zealand is to boil repeatedly in oil if they have a carved piece
which has developed a tension flaw during cutting and grinding.
The oil fills the air space between the laminae and it vanishes.
Trouble is they never disclose to their customers pieces which
hace been oil treated. Mind you, I have been guilty of it myself;
my wife wears almost daily an oiled piece I carved for her about
25 years ago, but I wouldn’t sell oiled work without disclosure.
I rarely sell anyway.
Try to find someone who is carving and polishing jade frequently
and get them to let you do a hands-on polish under their
supervision. The people in the Hokitika jade factories on the
West Coast NZ did exactly that for me. Purely out of kindness
and interest. But do let me know how you get on, please. Cheers,
/\
/ / John Burgess,
/ /
/ //\ @John_Burgess2
/ / \ \
/ (___) \
(_________)
