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Fixing contaminated laps?

Gem Related Discussion
#1

My fairly new Greenway polishing lap is contaminated. I thought I was dealing with leftover scratches or subsurface damage, so I started a new stone and both preformed and faceted the pavilion entirely with a 600 NuBond lap (big stone, took forever). The finish was a lovely uniform matte surface. I washed the Greenway again (just dishsoap and water, no scrubber of any kind), put it on the platen and laid down a girdle facet. Boom, two not just scratches but gouges immediately dug into that lovely surface.

Is there anything I can do to get the contamination out of the surface, or is it trashed forever? I didn’t even cut but a few stones with it but I left it out unprotected in a room that was then used by a bunch of people for gardening tasks. There are more than just a couple of places I can mark and avoid, I can’t find any area that doesn’t have at least one scratch. The first stone it scratched up was a citrine, the new one that I preformed and faceted on the Nubond 600 is a beautiful synthetic alexandrite.

#2

https://photos.google.com/photo/AF1QipPVQKz_5ZftgsTVi6Nlit2ucV41fJ77SKRNBAiI
Here’s the synthetic alexandrite before I dug two giant gauges out of the girdle on one side.

#3

Update, the scratches were across the sharpie marker but didn’t scratch with chrysoberyl (mohs 8.5). So probably the contamination is quartz instead of loose diamond from a cutting lap? It did cause scratches on the citrine I was trying to polish earlier. Anyway, question remains, how to clean a contaminated polishing lap.

#4

Hi Willowdale, Best thing to do is contact Gearloose the creator of the lap. Ask him about having it resurfaced. It should be able to be done.
Good luck,
Michael

1 Like
#5

You didn’t mention the type of lap that has contamination. An experienced gem cutter gave me a tip for your problem on a BATT lap. This has worked three times and nothing of the sort has happened since. Get a package of the fine steel wool. With water dripping and wheel speed on low rub the steel wool across the circumference for 15-30 seconds. Remove it and wash it thoroughly with soap and water. At first I tried scrubbing it in both direction, but that required some break-in after. I find it is wise to work the surface for a bit, wash it again and off you go.
As for care and feeding of laps, especially polishing laps for Cerium oxide or Alimina A, dry them thoroughly, buff the surface with linen towel to remove the black oxide firmly adhered tot he surface to produce a nice sheen. Then store them in a plastic lap container. Rock Peddler sells them. Since managing the laps the way I describe, I have had absolutely no problem with scratches, even with large tables.
Good luck!

#6

The problem with a resurface of a dual ring lap is that the coated inner surface would then not be at the same level as the outer ring and that’s why you use one, to save time. If the resurface is only slightly lower than the inner polish surface, you could on a graduated mast machine just go up by a certain amount each time you switch, but this gets tedious.

In the old days, people would use a piece of synthetic and polish in various rings until the ring where the contamination occurred was located. Then it would be a matter of stopping the lap and trying the piece of synthetic over various places until the scratching was located at one point on the lap…then you dig out the contaminating particle. If you have several, you do this over and over. You will have places on the lap which are faults, but if you are careful, they can be very small.

All of this said, it would probably be better to just return the lap to Gearloose for salvage of the metal and get a new one…less trouble and restored convenience. I love my Greenway, it polishes so darn quick!
royjohn

#7

Thank you, I though I’d heard this trick before and this is what I’ll do. It was a Greenway, and hopefully it’s not embedded and I can loosen it off with the steel wool.

I’ve been trying to polish now with 60k diamond on a brand new Batt lap and on a brand new Darkside lap and I cannot succeed with either one. I’m so frustrated. I know I’m not the first beginning faceter to have trouble polishing but I try everything and nothing works. I got a good prepolish on my stone with 8000 on a Tin+ (Gearloose), then when I went to 60k it frosted the facets!!! The 8k prepolish was beautiful, to go backwards to frosted, on a new lap, using a new 60k gealoose stick, when I had cleaned everything like a crazy person - machine, stone, table, myself - was maddening. This was a synthetic alexandrite (chrysoberyl not corundum). I never did get the barion facets to a 10x flawless finish.

I wish I could go to a club and have someone watch me for five minutes, I’m sure it’s something with me using too much or not enough diamond, too heavy or too light a touch, who knows.

I know this is newbie pain / dues paying, but it’s so frustrating!

#8

Royjohn, I’m hoping as BRitchie suggested that I can break it loose with steel wool. I hate to admit that I messed up a new lap within an hour of use. And I’ve now had trouble polishing with a Batt and Darkside - no big scratches, just “frosting”. I don’t think I’ve contaminated them, I’m just not loading or using them right.

#9

Steve L.

My feelings say that the laps needed to be conditioned before polishing facets. On the greenway lap I’ve used green scotch bright with medium pressure mild speed and lots of water to remove contamination. Than use a flat piece of quartz for conditioning the lap.

#10

Thanks. I’m going to try the steel wool or scotch brite treatment.

#11

NEVER, NEVER use Scotch Bright kitchen pads. The ones with a yellow sponge and a green, coarse net plastic back. The manufacturer doesn’t like to talk about this, but the tip-off is when they tell users NOT to use them on aquarium glass. Very suspicious! It took me a while to find the data, but on one web page I found that the green back contains Alumina. Of course it had to be there to work so well for kitchen cleaning. The step wool works well.