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Polishing rainbow obsidian


#1

Hi! What do I use to polish rainbow obsidian? How do I polish
rainbow obsidian? I noticed that polishing obsidian on a leather
with super cerium oxcide or linde A scratches the stone. I also read
that a wet polish is better than a dry polish. Thanks for your help
in the matter.

Anne


#2

Anne, The standard for polishing any obsidian is cerium oxide on
FELT…not leather. Obsidian is, after all, glass albeit natural
glass, is a member of the silica family and thus polishes perfectly
with cerium. The medium should be kept moist…not wet as the stone
will slip across the surface and little polishing will occur.
Conversely, if left to dry, the powder will clump and scratch the
stone.

If you MUST use leather, be sure to keep it moist as well but,
leather dries out more quickly than felt and can be a problem. Linde
A is not needed.

Cheers from Don in SOFL.


#3

I’ve always used cerium on leather to polish obsidian, but it’s
tricky.

It is all in technique; the polish only happens for me during the
brief time as the leather dries out.

Moisten the leather a little and apply a thin slurry of polish, work
the stone pressing fairly hard, as the leather starts to dry it will
drag on the stone harder, it is during this increased dragging that
the polishing occurs.

Stop polishing before the leather gets too dry, the heat can easily
crack your stone, also as you have found, the dry cerium can scratch
as well.

Re-moisten the leather and start again. You may have to repeat the
process many times but check your work as you go, you will probably
find polished spots and dull spots showing you where you need to
work.

It’s tedious but worth the effort.

Have fun and good luck!
Mark


#4

My standard method for polishing this material is using a slow
turning, large diameter wheel covered with a piece of office style
carpet. It is about 1/4" thick. The wheel is 12" in diameter and
turns at 400 rpm. I use Cerium Oxide almost exclusively for my
cabbing activities which includes doing a lot of Obsidian. I like the
carpet because the ideal not-too-dry, not-too wet condition lasts
about 5 minutes before you have to rewet the wheel with a spray
bottle filled with water and a few drops of liquid hand dishwashing
detergent. You can see examples of the polish that I achieve in an
article that I wrote on Catseye Obsidian in the July 2010 issue of
Lapidary Journal - Jewelry Artist magazine. The Catseye obsidian cabs
are made from Davis Creek Rainbow Obsidian. I’ve used the
carpetpolishing wheel method for over 30 years.

Bob Rush


#5

I do hope you have seen Bob Rush’s polished obsidian, it is
remarkable, luster, it pop’s and watch for his work in all lapidary
arts. Amazing lapidary master.


#6

Bob, Thanks for your input which I am sure will answer this question
for many people. I previously had mentioned using a felt pad with
cerium oxide to polish obsidian as well as any of the stones of the
silica family. Our two ideas are basically the same as, assuming you
are using woolen carpet, which is also what felt is made of. The
possible difference is that the carpet has been made into threads
which might hold the moisture a bit longer than felt. I also agree
regarding the slow speed. I rarely turn my polishing wheels at over
200-400 rpm unless polishing jades and certain other stones when I up
it to 900 rpm and use either tin oxide or Linde A.

Cheers from Don in SOFL.


#7

Hi, I use a coarse felt and cerium oxide. I use carpet for polishing
with my vibro lap. Last longer than felt pads and cheaper as well.

Nick Royall


#8

Don, Actually I use the thin (1/4" thick) office type carpet. I’m not
sure what the fibers are made of (Nylon?) but they have small 1/8"
high loops that retain the polish and water for a long time. I
usually dumpster dive for left over scraps from office remodels. I’m
sure they are not wool, though.

Bob


#9

Interesting. Wasn’t aware that other types of material would work so
well. I’ve used leather, wood, and other polishing mediums on various
stones but only wool when it comes to obsidian. Always learning
something new!

Thanks
Bob. Cheers from Don in SOFL.