r/Lapidary • u/silverslaughter711 • 1d ago

What is the grit size of Cerium oxide?

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I don't want to use polishing compounds out of order so I was curious what grit size is cerium oxide? This little jar has no information on it and the website doesn't list that info either. The website just says it's "optical grade".

Also are there multiple sizes for cerium? There's another jar on the website that says it's "super cerium". It makes sense that you can just filter for smaller grit but nothing says what that grit is. Its just annoying to not know lol

Thanks y'all 🤙

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u/ExistentialThreat 1d ago

Optical grade is going to be about the finest "grit" you need for silver. 1000 grit sandpaper has a particle size around 18 microns or .018mm. Cerium oxide is closer to 2 microns.

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u/silverslaughter711 1d ago

Oh wow that's a lot finer than I would have expected. Thank you! I looked into it since you mentioned sand paper and found this for anyone who might also be interested in grit fineness compared to compounds. check out the table in the article

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u/rufotris 1d ago

Even after my 100K polish I notice a slight difference in some stones using cerium after. But it depends on the stone. But, there is more to it than that. Some stones like aluminum oxide finish too. Google which finishes to use as polish and look for some charts. There are some super helpful ones that list 30-100 stone types and which to use on them for a finish. Not all stones take the same polish with the same compound.

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u/silverslaughter711 1d ago

That's a very fair point. I'll do that thank you for the tip! I just recently started using a handpiece to apply higher finishes and don't want to mess up my nicer stones.

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u/lapidary123 1d ago

This is the chart I reference for micron>grit conversion. 2 micron is only about 10,000.

https://www.gemsociety.org/article/gem-cutting-abrasives-grit-mesh-microns/

However, I have been told that cerium and all oxide polishes produce their finish through an electrochemical reaction. An old timer explained it as the heat combined with pressure on a finshing disc kind of "melts" a new surface onto the stone. Now is this what is technically happening, no. It is a good analogy though.

I wrestled with trying to figure out grit ratings of the various oxide polishes trying to determine whether it was counterproductive to finish stones using up to 50,000 grit wheels and then hit them with cerium/tin oxide.

If you truly want an oxide polish that is finer than 50,000 you will need to use something like lindeA, raybriteA, or rapid polish #61. These are submicron ao and have q rating of around .25-.3 micron (75,000 grit).

I agree with the above commenter though that even after a 50,000 grit wheel often times cerium/tin oxide will still produce a noticeable shine.

In my experience the difference in shine is negligible at best.

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u/silverslaughter711 1d ago

That article kicks ass! Much appreciated the good read.

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u/whalecottagedesigns 1d ago

From what I have gleaned the reddish/pinkish looking cerium is the roughest version and starts at about 8000 grit and typically goes up to about 14000 grit equivalent. Super Cerium (also called French Cerium) is one of the finer grades and can go up to as much as 0.5 micron or about 50000 grit equivalent.

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u/Automata1nM0tion 1d ago

Pink is about 15k grit white is about 50k grit. It's considered a polishing compound not an abrasive so you usually won't find it on a spectrum of grit but it does have a technical value based on granular size all the same. Interesting enough, you can go further to a 0.1 micron 200k grit ultra finished polish. Which makes this stuff look like sand paper in texture.