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Author Topic: Art In Stone - Cutting, sanding and polishing Jade tutorial  (Read 680 times)

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Redrummd

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    • Art In Stone
Art In Stone - Cutting, sanding and polishing Jade tutorial
« on: March 14, 2018, 09:40:06 PM »

March 14,2018
Cutting Jade rough -

Fine grained Jades can be pretty much cut in any direction down to 1/8 of an inch without any problems. Top grade Jades cut with VERY crisp edges and that is the first thing I look for when buying a piece of Jade. 
The problems arise with lower quality Jade.  These usually show indications such as "chips" along already cut edges and in lines in the Jade running like the grain in a piece of wood.  If you have a Jade piece with lines in it you need to cut with the length run of the grain.  If you cut across the grain the Jade will crumble.  You also need to cut the Jade thicker than usual to ensure you do not get separation between the layers.  These layers do not always show in the Jade and it is referred to as "schistosity".  I and many others refer to it as "croissant" Jade. 

It is a bit weird in that these "croissant" Jades once cut and polished are VERY tough and will not easily chip or crack and some take a glossy polish too.  This is just one of the mysteries of Jade.

Sanding Jade -

I recommend NEVER using a metal grinding wheel to shape Jade of any quality.  Jade will "bruise" as it has a felt like composition.  The first evidence you will see of "bruising" is tiny white spots showing as these are spots fibers are pulling out or compressing and developing flakes.   In fact, Jade will sand much faster than grinding and sands very quickly with practically worn out sanding wheels specifically ones sold by Eastwind.   I do most of my shaping with worn 120 and 300 grit Eastwind drums.  Worn belts on sanding drums are next best while NOVA wheels are the slowest.

When you get past the 300 grit shaping the NOVA wheels produce the best results.  I think they have a harder flexible surface and give the smoothest surface with the least amount of texture.  It is very important to change the direction you are sanding every 10 to 15 seconds by at least 90 degrees.  This cuts down on orange peel and on swirling structured Jades it cuts down on undercutting.  Neither undercutting or orange peel can be eliminated on many different Jade's, you can just minimize the issue.  The final 330 and 600 grit sanding pattern would be similar to this pattern:  /////\\\\\/////\\\\\/////\\\\\/////\\\\\  This same pattern is used in all of the polishing stages.
Polishing Jade -
Jade can be difficult to get a good polish on due to the structure and nature of the stone.  It has a highly textured structure of intertwined mineral fibers that are both tough and they often run in many directions if the Jade has a swirling structure.   Most Jade is not the very fine grained Jade that will take a mirror polish so the real challenge is to bring the best polish possible to the Jade being used.

I have found that it helps to get the best polish possible by ensuring that each stage in the sanding process is completed to the point that removes enough Jade to get all of the texture removed that was disturbed in the previous sanding stage. I do this by marking the Jade being polished with an aluminum marking stick at the 600, 1200 and 3000 grit stages and sanding to ensure every bit of the marking is removed before going on to the next stage.  Once the marks are removed I continue to sand for about the same amount of time it took to remove the markings.  I use NOVA sanding wheels and sand and polish up to 14K for nearly all stone I work including Jade that does not start to show signs of “orange peeling” or undercutting at the transitions layers in swirling Jade.  I refer to the undercutting as “texture” in the stone. I check the Jade piece after each sanding grit to look for worsening texture or orange peel. If I see either has developed I drop back to the previous grit and get the Jade sanded to the point it looks its best but polish to at least 3000 grit even if texture is showing.

Most Jade polishes well on high dome pieces on nearly worn out 1200 and 3000 grit NOVA wheels. You sand to 1200 grit as normal with a wheel that is not nearly worn out and then change over to your nearly worn out wheel(s). Turn the water drip on the sanding wheel REALLY low and polish by starting in the slightly wet area of the wheel and moving to the pretty much dry area and use light pressure until the wheel starts to "grab"/"scuff" and then repeat until you get a fairly shiny polish on the 1200 wheel. Go to the 3000 wheel and repeat until you have a good polish and then try 8000, or 14K to see if the Jade will take a glass like polish. With flatter and wider pieces this does not work easily as the belts do not drape well onto the nearly flat areas.  Jade polishes significantly differently between well domed pieces and nearly flat pieces.
For lower grades of Jade you will find it is not possible to get a glossy polish and that the Jade wants to develop a surface similar to that on an orange.  This is called "orange peel".  These lower quality Jade pieces will take a good shine even if they will not take a nice polish.  I have found that ZAM and Fabulustre give me the best results on these more large grained, difficult to polish Jade's.  Once you finish getting the best polish possible with the worn NOVA 1200 or 3000 grit wheels you switch over to Fabulustre and ZAM.   You do not need more than 5 minutes between both wheels with probably three short passes on each one alternately. For Jade, the Fabulustre is usually the only buffing compound I use but I have the wheels on the same buffer and if I think the stone might improve a bit I go from the Fabulustre to the ZAM and if it does improve, I go back and forth until I can see no further improvement. Fabulustre seems to work best for lower quality big grained Jades. The buffing is done VERY lightly, almost like you are trying to dust the piece off. At most a few ounces of pressure should be used and if any of either the ZAM or the Fabulustre start to stick to the piece you are buffing, you are using too much pressure.

I use a Sears Craftsman variable speed 6 inch grinder at its high speed for the buffing. 8 inch buffing wheels will fit on the 6 inch machine. It is set up with both a ZAM and a Fabulustre wheel. Buffers can be very dangerous so extreme care must be taken to ensure you do not catch an edge of the piece you are working on the wheel while buffing.

"Secrets"
* Eastwind Diamond sells a flat lap they refer to as "Diamond Dot Disks".  These have a magnetic backing.  These disks can be safely used to "grind" most Jade without causing harmonic vibration issues. 

* Often I use spit for the very last scuff polishing on Jade!  That is kind of my "secret" stage to Jade polishing....


Jade general information –

Both nephrite and jadeite often have veins (Jade root), flakes (feathers), blemishes (black Magnetite spots etc.) and streaks running through them, though these natural structures are not usually considered to be regarded as flaws. On the contrary, some of these patterns and structures are considered to be particularly valuable. In both jadeite and nephrite, the way the color is distributed varies a great deal. These internal characteristics in highly translucent Jades such as Polar and Siberian Nephrite Jades can refract light reflected from the metal of the knife along the spine, blade well and bolsters and show the transitional zones of color. Refraction is the change in direction of a wave due to a change in its speed. This is most commonly observed when a wave passes from one medium to another at an angle other than 90°. Refraction of light is the most commonly observed phenomenon. Refraction is also responsible for other better known phenomena such as rainbows and for the splitting of white light into a rainbow-spectrum as it passes through a glass prism. I believe that the actual sawing of the slabs of Jade pulls out some fibers which can contribute to the occasional refraction show along the points where the Jade sits against the metal. This is a specific issue only with the use of highly translucent Jades on knives as bangles and jewelry Jade works do not have the metal of the knife along the spine, blade well and bolsters to refract the light through these nearly transparent Jade structures. 

If you closely examine your Jade, you may be concerned that it's not "perfect". Jade is a natural stone and has characteristics that you might think are flaws, but they are naturally occurring characteristics that help gemologists identify genuine Jade and Jadeite. There are always variations in Jade. If your Jade is "perfect", it might be an artificial, imitation stone or even glass "Jade", not a genuine Jade. The only true flaw in Jade is a crack line, see definition below.

Clarification or Cleaving Veins: interior crystal irregularity of the interlocking fibrous structure, may appear as a crack that runs through the width of a Jade art piece. These are not considered to be cracks or damage. Se also jelai below.
Chime: Jade chimes like a bell when struck with a chiming instrument. The finer the grain , the higher the chime.  Chime is one of the tests to determine quality of Jade and Jadeite. Also see "stone lines" below.

Cui: In the Jade trade, called "wings of flies".. Naturally occuring tiny structures that resemble the wings of flies. The more coarse the Jade, the more "cui" will be visible.

Crack line: Caused by a direct hit, geological deformation and mining.  This is really a crack. It is seen on the surface of the Jade and can be felt on a polished piece.

Grains: Intergranular cracks in the fibrous structure of genuine Jade or Jadeite. Not considered to be cracks or damage, a natural occurrence in Jade.

Fei Cui: The green color that is the classic color of Jade.  In a lot of Jade you can also see "Water Jade' - A near colorless translucent streak sometimes known as "Glass" Jade.

Gem Quality: Jewelry grade Jade that is evenly colored and with no blemishes or flaws easily visible. Inclusions: the natural Jade pattern you can see inside Jade which may look like streaks and spots. Commercial Jade is often bleached to remove inclusions that are not attractive, like Magnetite black spots. I do not buy or sell bleached Jade and the inclusions are considered to show that natural-ness of the Jade.

Jade: The term "Jade" in this article refers to Burmese Jadeite and Nephrite Jade. Jadeite is also called "Jade".

Jadeite: Jadeite is a gemological term for Jade that is mined in Burma (Myanmar) and is also called "Jade". There are also small deposits of Jadeite in other countries, include the USA and Canada.

Jade root: Looks like tree root, a natural occurring formation in Jade. These lines absorb color during the formation of Jade. Sometimes they look like cracks, can be seen unmagnified, and you might be able to feel it with your fingernail if it is on the surface. This characteristic gives Jade beautiful coloring and is not considered to be a flaw.

Je lai: natural imperfection in Jade stone, may appear as a crack and sometimes you can feel it, but it is not considered to be a crack, but rather proof it is genuine Jade. See also Clarification or Cleaving veins above.

Geological pressure during Jade development causes the structure of the Jade to be different throughout. You can see this in all Jade under 10x magnification, and you can often see it without any magnification. It looks similar to cracks in ice or “feathers” and might look like a crack, but is not a crack. It is naturally formed. "Fine grained" Jade has fewer of these stone lines, and the "chime" if finer grade Jade, is higher. See "chime" above. 

There are many articles written about “cracks” that can be seen in Jade. You can use a bright light and see what looks to be cracks in most translucent Jade. These are NOT cracks. They are called je lai, part of the natural appearance of the Jade. These are also called Jade root, or hairline root, and are not considered to be cracks.

A crack is considered to be a crack if you can feel it with a finger nail on a polished piece. While I acknowledge that these hairline root-je lai are part of natural Jade, I know that some customers may see them as cracks and don't like to see these.

If you use a flash light to look at Jade you will certainly see something. There is a Chinese saying: "The carver always leaves something behind."  Jade art pieces and jewelry are hand made, and you may see nicks, scratches and even small internal pressure cracks, but these are considered to be part of the beauty of Jade and the uniqueness of owning a hand crafted item. They don't affect the durability. The less expensive art works will have more of these, while the more expensive ones have fewer.
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Jhon P

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Re: Art In Stone - Cutting, sanding and polishing Jade tutorial
« Reply #1 on: March 15, 2018, 07:20:55 AM »

Thanks, for sharing your knowledge. Always helpful
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Orrum

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Re: Art In Stone - Cutting, sanding and polishing Jade tutorial
« Reply #2 on: March 15, 2018, 10:36:06 AM »

Great info!   Maybe I will try jade again by this tutorial. Jade hates me but I love the finished colors and patterns others achieve!
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Jhon P

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Re: Art In Stone - Cutting, sanding and polishing Jade tutorial
« Reply #3 on: March 16, 2018, 08:01:17 AM »

You inspired me to pull out some pieces of jade and play around with them. Do a little experimenting.
California , Wyoming, British Colombia and Guatema jadeite
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