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Author Topic: New polish lap for oxides on softer stones.. garnet etc ??  (Read 740 times)

ianRobinson

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New polish lap for oxides on softer stones.. garnet etc ??
« on: September 20, 2018, 05:56:02 AM »
Hi
I have just finished cutting the pavilion on my first rhodolite when I realized I need to polish with oxides.
Presently I use
Copper   25,10,6  micron
Batt      3 micron  (accidentally contaminated polish lap)
Zinc  0.5 micron
Ceramic   0.25 micron
and a corian for oxides but this seems to cause too much heating.

I am likely to be doing a lot of cutting this year esp. of softer stones such as garnet so probably worth buying a lap.
Pure tin has been recommended. I have looked at gearloose's laps such as the darkside but am getting lost in a world of choice.

Can anyone recommend a good long lasting lap for these slightly softer stones?

Thanks

ian
« Last Edit: September 20, 2018, 06:06:33 AM by ianRobinson »

Gem Ranger

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Re: New polish lap for oxides on softer stones.. garnet etc ??
« Reply #1 on: September 20, 2018, 10:19:43 AM »
Hi Ian,

The most commonly used (and effective) polishing laps are the 'type metal' (alloy) laps. Pure tin is too soft. Your prepolishing lap should be copper. Don't 'score' either lap, but a touch up sanding with 240 grit wet & dry is advised if the laps are too shiny.
I use a vaseline / kerosene / diamond powder mix as the prepolish & polishing compounds - 3,000 to 6,000 diamond for the prepolish, 60,000 for the polish. Add a bit more diamond to the mix when faceting harder gems like topaz & sapphire. There are premixed compounds & sprays available if you prefer. Use small chamois squares to distribute the media on to the laps. Keep each well separate to avoid cross contamination.
Garnets polish easily and I'm sure you'll achieve the outcomes your after.

slomoshun

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Re: New polish lap for oxides on softer stones.. garnet etc ??
« Reply #2 on: September 20, 2018, 01:36:34 PM »
The Gearloose Darkside lap with their 60K Diastik should do a fine job. Jon has said it will polish anything. I've used the combination to replace Cerium oxide. Don't irrigate the lap. Instead, mist it with a spray bottle and run it almost dry.  Apply just a couple of dabs of the crayon at a time, and refresh as needed.  It polishes fast, you can jump to it from a 1200.

When new the Darkside's surface seems too rough, but other than being noisy at that stage it works fine.  After a couple of stones it will smooth nicely.

FlashGP

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Re: New polish lap for oxides on softer stones.. garnet etc ??
« Reply #3 on: September 22, 2018, 10:46:18 AM »
My 1st polishing lap is a Darkside and I was supplied 50k diamind powder.  Bob Boddington told me to apply a tiny amount on the tip of a toothpick to the lap, add a couple of drops of diamond extender, make a slurry, spread this over the lap then wipe off with a tissue,  what's left behind is used for polishing. 

It works even on quartz, but oxides are faster with quartz. Here I use Al Oxide, Zirconia and Cerium Oxide Bat Sticks.

The Darkside is my go to lap for comp work, but now I use makeup removal wipes and home made 50k diamond spray, sprayed onto the face wipe,  4 drops of snake oil instead of diamond extender and wipe on lap.  This way stray diamond does not find its way into the faceting machine mast or bearings.

the trick is to use so little diamond you can't see it.

Yours Sincerely
Flash (Gordon)

ianRobinson

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Re: New polish lap for oxides on softer stones.. garnet etc ??
« Reply #4 on: November 15, 2018, 05:01:46 AM »
Hi

thanks for all your advice. i got a Darkside lap and am impressed. It worked well on garnet and also Lithium tantalate both of which failed on zinc, ceramic and corian.

Rather impressed -  easier to use on sapphire than my ceramic.

ian

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