Tips For Polishing Synthetic Corundum

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PinkDiamond
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Tips For Polishing Synthetic Corundum

Post by PinkDiamond »

This is from the Gem Society and could come in handy for some of you. ;)

Tips For Polishing Synthetic Corundum
Image
Synthetic or lab-grown corundum (ruby and sapphire) has the same physical and chemical properties as natural corundum. Polishing synthetic corundum can leave pits on the gemstones. Gem cutters can avoid this problem with the right tools and techniques. “Artificial Ruby Hemisphere Under a Monochromatic light” by D.328 is licensed under CC By-SA 3.0

"Question

I’m having a problem polishing synthetic corundum. I hope you can help. I’m cutting synthetic corundum, small 4 x 4 x 4 tri. The problem is I’m leaving pits in the stone after polishing.

I’ve tried almost everything, from tri-laps, ceramic laps, 3000 NuBond, to lucite w/8000 diamond. I’ve varied the speed, used oil, used water. I’ve cut with 325 NuBond and then polished. Cut with 600 NuBond and then polished. Cut with 600 dia. lap and then polished. Tri-lap 600, tri-lap 1200, same result.

The NuBond laps are well used. Could this be the problem. The best solutions I’ve found for polishing synthetic corundum are to cut ½ degree off of finish and then polish or polish on a corner with 3000 NuBond. This works somewhat, but it’s not great.

I have 18 of these stones left to cut and polish. I’d appreciate any advice.
Answer

Polishing gemstones can be a mystery. However, what you’re experiencing is a common problem with polishing synthetic corundum. The NuBond laps are a bit gentler than nickel bonded laps but they leave pits that are almost impossible to polish out. There is a way around this, though. ..."

https://www.gemsociety.org/article/tips ... -corundum/
PinkDiamond
ISG Registered Gemologist


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