Joined: Tue Apr 05, 2016 7:58 pm Posts: 1424 Location: San Marcos, CA
What have you experienced or found that makes irradiated topaz harder to polish than other topaz? I have cut and polished my share of topaz of all varieties and from most to all commonly known locations as well as treated. I am curious why you say that about irradiated.
I use Diamond on all types of Topaz without issues. What makes it hard to polish is missing on orientation and getting a facet too parallel to the direction of cleavage. Usually people get the table in this orientation because the cleavage tends to make what looks like a perfect place to put the table in the rough.
Joined: Tue Apr 05, 2016 7:58 pm Posts: 1424 Location: San Marcos, CA
jleb wrote:
The neutron irradiation apparently makes some varieties brittle and hard to get past the microscratches.
What laps do you use and what polishing agent?
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topaz-preforms.jpg [ 230.46 KiB | Viewed 773 times ]
I have to ask know what power magnification your using to establish a micro-scratch. Not in my experience do I find any topaz per say to be brittle.
8" 360 Electro Plated and a 6" German Sintered 600 arbor wheels for preforming work on a Harbor Freight Tools Bench Grinder setup.
8" 600 Solid Import PolyPro and 600 Sintered Crystallite, I find the solid leaves a nicer finish on smaller rough and the sintered is more aggressive on larger.
3k Diamond powder with WD40 on a Batt, but have found the Tin+ is a better choice for topaz and harder gems.
8k Ameritool Grease Syringe believe it or not, 60k Waterbased PolyCrystalline Stiks (Gearloose) not sold anymore and I do use water, I guess you can use the new PAN Polycrystalline stiks, I just haven't needed to yet. This is done using a ZINC+/BA5T Dual zone Gearloose lap. I use this lap on pretty much everything except quartz and softer gems. It leaves very sharp facet edges, you need to break in the BA5T by just using it. I have another just BA5T lap that I use with WD40, have tried the other lubes but always go back to Wd40. It is easy to clean swarf from the dual lap with the combo water and oil, just remember to pull from the center outward with a water damp paper towel right across the 8k, then a wet wd40 paper towel from the edge of the 8k/60k joint outwards.
Typically the 8k isn't really needed just there if a facet needs a little bit of adjustment, and you don't have to change out the lap a reset the mast for lap height variances, etc.
Topaz is probably one of my favorites to cut, just doesn't get the big bucks.
Here are some preforms all irradiated material, with the electric swiss and london I process the rough differently as it is more cost effective.
Also I run an automated machine for calibrating cutting for jewelry accent stones. Then it is 600 sintered, Batt laps 3, 8, 13, 50k all with diamond powder and wd40. Smaller stones 8k then 50k, larger 3k then 13k with 50k table only. This is commercial cutting, why I asked how you classify a micro-scratch.
Probably more than you wanted to know.
Agreed identifying the cleavage can save a lot of headaches when your at the table stage, sometimes doing the table first can help if your comfortable at faceting that way.
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