New Mineral Named After GIA’s John Koivula
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 Post subject: prepolish and polish dual purpose lap contamination question
PostPosted: Sat Sep 14, 2019 7:51 am 
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HI
i have bought a dominatrix lap. outside area is batt and inside area is matrix lap. yet to receive it.
Thought it would save time to polish and prepolish in a go.

However i was thinking wouldn't the two different diamond compounds contaminate each other?
as i will be using 3000 diamond compound on batt(which is outter portion of lap) and 60000 compound on matrix(which is inside portion of lap)

whats your experience , those that have used such laps.
or have i made a mistake?


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 Post subject: Re: prepolish and polish dual purpose lap contamination ques
PostPosted: Sat Sep 14, 2019 8:43 am 
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GemologyOnline has a very useful search function. Searching for "dual laps contamination" provides lots of answers.
https://www.gemologyonline.com/Forum/phpBB2/search.php?keywords=dual+laps+contamination&terms=all&author=&sc=1&sf=all&sk=t&sd=d&sr=posts&st=0&ch=300&t=0&submit=Search
I use various dual laps with no contamination problems. The only drawback is that you can't polish the girdle without turning the lap over and using the back of the Batt band, and that requires a paper or plastic mask to prevent contamination of the inner polishing band lying on the platen. I use a separate polishing lap to polish the girdle.


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 Post subject: Re: prepolish and polish dual purpose lap contamination ques
PostPosted: Sat Sep 14, 2019 1:09 pm 
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Location: San Marcos, CA
14megapixel wrote:
HI
i have bought a dominatrix lap. outside area is batt and inside area is matrix lap. yet to receive it.
Thought it would save time to polish and prepolish in a go.

However i was thinking wouldn't the two different diamond compounds contaminate each other?
as i will be using 3000 diamond compound on batt(which is outter portion of lap) and 60000 compound on matrix(which is inside portion of lap)

whats your experience , those that have used such laps.
or have i made a mistake?

Actually I believe that the inner is a diamatrix. Slightly harder version of The matrix.
The concept in using is not hard, prepolish first wipe off, then polish wipe off. When cleaning lap always start in the center and move outwards, as not to push the outter diamond onto the diamatrix section.
With all polish laps there is a chance of cross contamination, every facetor has different practices to keep this from occurring and starts with your own habits of cleanliness.

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San Marcos, CA


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 Post subject: Re: prepolish and polish dual purpose lap contamination ques
PostPosted: Sat Sep 14, 2019 3:30 pm 
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So i guess its always better to have a separate lap for polish and pre polish.
Yes working with girdle will be a problem. Will have to turn over the lap or use a separate one.


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 Post subject: Re: prepolish and polish dual purpose lap contamination ques
PostPosted: Sat Sep 14, 2019 7:21 pm 
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Tom Smith at AdamasFacet has a new lap that he is making. The outer ring is a sintered diamond cutting/prepolish and the inner ring is Matrix polishing lap. The sintered is much less likely to to contaminate the inner ring.

I have been using this lap for a little time now and it is magic. Yes, it is more expensive, but worth it in finish quality, and time saved.

I think it saves the most time for those who are good pre-formers in their workflow.

Pre-form, dop, then lay the facets on, and polish with the Twister. Super fast, and increases yield.

http://adamasfacet.com/twozone.html


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 Post subject: Re: prepolish and polish dual purpose lap contamination ques
PostPosted: Sun Sep 15, 2019 9:56 am 
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I Have been using dual charged laps for years, and have never had in issue with cross contamination. I polish the girdle with the outer lap only, for the girdle this polish is more than ok. Most commercial cutters don’t polish the girdle at all. I use 8000 diamond not 3000 for the pro polish so maybe that helps too. 8000 is enough that you can move facets but does leave a little nicer finish than 3000.
I wouldn’t want turn over the lap, that’s just one extra issue to deal with.

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www.precisiongem.com


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