This list digest contains the following message subjects:
1. LapDigest News for Issue No. 182 - Thurs 12/2/98
2. NEW: Polishing Pads
3. NEW: Ivory Flakes for Tumbling
4. NEW: Are There Any Books On Cab Polishing?
5. New: Heat Treating Smoky Quartz
6. RE: Polishing Jade (Nephrite)
7. RE: Polishing jade
8. RE: Polishing jade
9. RE: Need Information on Production Machines
Subject: LapDigest News for Issue No. 182 - Thurs 12/2/98
Last summer I heard that a great article on polishing jade
had appeared in Rock & Gem. I got a copy, turned to the
page and started reading, and after finishing, looked back
at the first page and was surprised to find that it was
written by our own Dick Friesen! Was also pleased to see
that there was a picture of him; that was the first time
I'd seen him.
Well, he said he would write up something for us which
would summarize a lot of what he had found from his
experiments in polishing, and I am happy to present it
below, and recommend it for your reading.
Now, about our website. We started it on October 15, and
November was the first full month it was up, and we had
on the index page during the month!! Almost unbelievable!!
Upcoming on the website: many more thread files, a great
show of NZ jade carvings by member John Burgess, and more
magazine length articles from LD. And more graphics! We
don't lack material right now, but I just don't have enough
time to organize it and put it up. (And I'm trying to learn
Please work and play safely, and - as always - have fun!!
Subject: NEW: Polishing Pads
by Dick Friesen
To start, it may help to describe what is probably the most
common polishing process.
After the stone has been properly prepared for polishing
(whatever that means), the polishing compound (usually one
of the popular oxides) is mixed in a liquid (usually water)
and applied to the polishing pad. The stone is held firmly
against the rotating pad until a pulling is felt and the
stone is then moved against the pad until the entire surface
has been polished. If the polishing compound dries out
during the process, more compound and water is applied to
keep the pad in a "damp/dry" state.
Obviously there are several variants on this but the
question at hand is: which pad works the best? Well I don't
think there is one pad that is really "best", just a better
choice for the stone, technique and circumstance. So how do
To start with, it helps to remember that all the pad is
there for is to hold the polishing compound. It does not
DIRECTLY do anything to the polish. Almost anything you can
think of that will hold the compound can, and has been,
used as a polishing pad. Wood works very well, many people
like felt, soft leather is very common, phenolic wheels are
replacing maple for diamond compound (more common in
carving), one dealer recommends the back, or paper, side of
sanding disks, there are several sources of urethane pads,
the list is almost endless.
Remember when polishing stones in a tumbler there is no pad
at all (well, sometimes leather scraps are used to keep the
stones from hitting each other). An interesting technique is
used sometimes when critically shaped objects are being
polished. The compound is suspended in a moving liquid
surrounding the object. This technique is sometimes used in
the laser industry for lenses. For us, the pad is first a
convenience to hold the polish and second, it is used to
help the liquid evaporate down to the damp/dry state by
friction heating of the stone. This speeds up the polish.
You could polish in the wet state, it just takes too long.
So anything that meets these criteria might work, at least
on some stones.
So if the pad doesn't do anything and all these things work,
I can just use anything I want, can't I? Nope, life is never
that easy. The pad may not directly do anything but it sure
can indirectly mess you up. If you are polishing agate or
harder stones you can experiment with almost anything but
for anything softer you need to be more careful.
Tin oxide on soft leather is a good choice for gem quality
turquoise but hard leather can scratch it. If you are using
stabilized turquoise, the soft leather can scratch it. For
turquoise a safer choice is ZAM on a soft muslin buff, the
same kind that is used with rouge to polish silver. ZAM, by
the way, is a mixture of chrome oxide, aluminum oxide, and a
binder. This mixture sounds like it would be a better choice
for hard stones rather than turquoise but the softer pad
seems to keep things under control. ZAM on muslin also works
very well on most plastics. Tin oxide on soft leather also
works well on African malachite.
I like aluminum oxide on soft leather for tigereye. I find I
have fewer problems with the fibers pulling out than with
any other combination. I think the pulling, or not pulling,
fibers is more a function of the pad though rather than the
The harder pads, wood, hard leather, phenolic, etc. help to
keep the surfaces of stones that under-cut smooth. I find
though, that I sometimes have to follow these harder pads
with a soft leather pad to get the final polish I want. This
doesn't always work but it works often enough to be worth
considering on most softer stones. I use 0.3 to 1.0 micron
aluminum oxide first on the hard pad, then follow with 0.2
to 0.1 micron aluminum oxide on the soft pad.
I have twenty or more polishes I use so I tend not to use
the urethane or felt pads much. It isn't that they don't
work, they are just too expensive to use in quantity. I have
been able to get leather scraps from leather shops,
sometimes for free, that I cut into four inch circles. I use
Chrystalite's four inch Flexodiscs and just replace the pads
as needed. Frequently there are 12" x 24" leather scraps at
Quartzsite for a buck, you can cut a lot of 4" circles out
One problem I have had with the leather pads is when I add
vinegar to the polish. Vinegar seems to speed up the
polishing process on some stones but it appears to harden
the leather thereby shortening the pad life. The vinegar
hardened pads don't hold the polish as well and leave the
pad unpredictable in terms of what it will or will not
polish. As long as I can get cheap pads it is worth the
shorter pad life to speed up the polishing. Shorter is a
relative term, I still can get several months life from the
vinegar hardened pads.
I do use hard felt knife-edge wheels to polish quartz or
agate when I am carving. They get into the cuts well but the
polish itself is no better, or worse, than the leather pads.
Unfortunately individual technique is probably as important
as the pad itself and the best answer is to try as many
different pads as you can to see what works the best for
you. Just don't worry too much about it. Just trying a few
pads may make you think about what you are doing enough to
change your technique to match the pad rather than the other
Subject: NEW: Ivory Flakes for Tumbling
To replace Ivory flakes, how about using the Ivory soap bar
and an old four sided metal grater on the most appropriate
(Hale's note: Great Idea, Terrie. But as I understand it,
the flakes and the bar may have different formulations and
a flaked bar may not work. Anyone actually try grating or
flaking a bar and using it in tumbling? If so, write and
let us know how it worked. [You can also flake it using a
Subject: NEW: Are There Any Books On Cab Polishing?
I have been in the lapidary hobby for 25 years and I have
yet to come across a comprehensive book on cab polishing.
One that really addresses all materials and the best
polishing medium and equipment for each. If anyone knows of
one, please let me know. Thanx Bill
Subject: New: Heat Treating Smoky Quartz
In a review of November issue of Rock and Gem, the authors
<<Another interesting fact is how smoky quartz can be baked
inside a loaf of bread to heat treat it from brown to deep
yellow (citrine). This is a risky attempt though as it may
need to be baked three or four times and you run the risk
of the stone exploding during each baking.>>
Never had such a great belly laugh in all my life. I called
my wife over and explained this post, we cracked up. Why put
the stones in a loaf of Bread? I guess there is some logic
to it to act as a heat sink, avoiding some breakage. But on
the low temperatures needed to turn the Smokey to Citrine,
the breakage is minimal. Specially when you weigh it against
being able to see what you are doing.
Get a lighted interior glass door household toaster oven.
Convection is best, you have small fans inside to distribute
the air evenly for less breakage. Look through the glass
door while you heat the stone. Then take it out when it
turns. The way this person is doing it, some will overheat
to white because they cannot see, and think about all the
time wasted and what about all the singed loafs of bread?
Hey they tell me there are people starving in Brooklyn.
Subject: RE: Polishing Jade (Nephrite)
There was an excellent article in Rock and Gem within the
last year on Polishing Nephrite. One of the most interesting
suggestions was that diamond and jade don't get along, and
it's true. I tried using a worn 600 grit, you heard right,
carborundum disk and that went far towards a good polish.
After that I think chromium oxide on wood is recommended.
But I'm not sure of that. The 600 carborundum is a major
(Hale's Note: The article you are talking about was written
by Dick Friesen, who is a member of this list, and who wrote
the lead paper above. In the R&G paper, Dick detailed a
series of experiments he had made on polishing jade, gave
the results, and finally drew conclusions. In the paper
above, he continues to draw conclusions from his research
and from his experience.
Subject: RE: Polishing jade
Years ago I was stationed in Korea and a local taught me
to polish jade with a worn out 600 grit belt ran dry or
just about dry. Work really good.
Expressions With Metal
Subject: RE: Polishing jade
In a message dated 11/30/98 11:41:31 AM, you wrote:
<<Now, that may well be due to the jade itself that I have
(various pieces of British Columbia nephrite) and not to
the technique. Perhaps it works for some jades and not for
others, or for some people and not for others.>>
I have polished many pieces of BC jade....I mean a lot,
and the best success I have had is to bring it to a
pre-polish with a 1200 grit diamond wheel/lap and then
polish it hard and hot with 8000 mesh diamond compound. Wet
your piece and lap (I use Crystallite pads) with a light oil
like Crystalube and work it with high speed until it gets
hot and starts to show a shine. You can take it to a higher
polish if you want using the same technique with finer
compounds like 14000-100,000, but I am sure you will be
satisfied with the 8000 polish. It may take some time and
technique but it definitely works.
Subject: RE: Need Information on Production Machines
(When this query came in, I sent it to Mark Liccini and
asked him to respond, as Mark knows more about production
machinery then anyone else I know. His response in given
<<The production capacity cabochon shaped stones is about
500-1000 stones per month. I would appreciate it if anyone
can tell me what machines and consumables are needed to
fulfill their requirements and where is the best place to
be able to obtain them.>>
The expenditure for automated machinery is not practical on
the volume you project. My first suggestion is to associate
with a professional factory in a low labor country. Let's
take just the drilling you mentioned as an example. You will
pay $10-20,000 for the smallest quality ultrasonic drill
(Imahasi, Japan) But you can contract 1,000 holes to be
drilled for less than a penny each.
If your project must be done in house, you might consider
semi-automatic equipment. Hand crank units out of Idar
Oberstein, Germany, can only cost $500-2,000 each. These
will practically increase your efficiency and productivity.
They will also quickly give your product uniformity, a most
important point to consider when weighing hand work against
these machines, assuming your working material is plentiful
and of low value. When dealing with rare commodities there
is no substitute for hand and eye.
Not knowing your specific application, I cannot recommend a
manufacturer, but a trip to Idar would be well worth it.
You will readily find companies that will even design to
your exact task.
Hale's Note: I read the referenced query and immediately
sent a copy to Mark, asking him to comment on it, as he
knows more about production of lapidary items than anyone
else I know. This was his reply! Thanks, Mark. You guys
are a great resource for LD!
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