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 Post subject: Polishing Woes
PostPosted: Sun Mar 14, 2021 3:38 pm 
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I decided, as my Boring Covid winter project, to learn how to facet. After a few mishaps due mainly to human error, I've managed to figure out machine and procedures and produced a few (to my eyes, absolutely brilliant) stones.

Cutting and Pre-polish are working just fine. I've found that I've developed an almost mystical reguard towards my now well worn favourite laps.

BUT Polishing!!!
I started with the Cerium oxide on a plexy lap. I eventually figured it out and got some nice polish. I then discovered Ultralaps which are much easier. So far so good.

I have now run into a citrine that resists every effort. I get a lovely polish, turn to the next facet, and find it's covered in scratches. After cleaning everything, re prepolishing, I once again get the same scratches. If I skip this facet, everything polishes in 5 seconds. I've tried light, medium and heavy pressure, I changed direction of polish, I've used lots of water, almost no water and everything in between, I've also tried every speed of the lap, no improvement. Is this a cursed stone?

I tried switching to tin oxide because that is what I used when I cut cabs a lifetime ago, but that did not help.

Do I just give up on this (actually these stones,) I gave up on the previous one too.

I have a tin alloy and a copper lap but I've not used them yet. Would diamond powder work better and get around this scratching problem?
I'm also more than a bit confused about how to prepare the laps, Mr. Google gives conflicting instructions. Some suggest scoring, others promote a bearing wheel to push in diamond, still others spray diamond on a clean lap and polish away.

How do you polish tricky quartz? I'm at my wits ends, what little there was.


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 Post subject: Re: Polishing Woes
PostPosted: Sun Mar 14, 2021 4:39 pm 
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SO, to get this right the problem is with both the Plexy (whatever that is) lap and ultra laps? Do you have a chrome ultra lap, assuming your talking about the thin film type, try that if you have one. The fact your implying it is more than one stone your getting one facet that will not facet seems odd to me. Diamond as a finish polish on quartz can be as troublesome as what your stating, but I have done it with success, but usually follow with cerium on a composite type lap afterwards.
Scoring is rather outdated with the newer laps and is more of a personal preference. The concept is that the scoring gives particles that do not breakdown a place to fall into as to help prevent the fine scratches that can occur. I have and use both scored and non-scored, and the method of scoring the lap can be done in many ways. Using a tool or bearing to press diamond into a lap is charging a lap, and you can find videos of different ways to do it on Youtube, as well Gearloose has video on charging the Batt lap on his site as well. Why give up, find out what it takes to get over the hurdle, so the next time you need to deal with, you have some technics in your knowledge bank.
There is some Quartz that has particular phenomenon, I forget right know what it is called. Maybe you have some, just a thought.

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 Post subject: Re: Polishing Woes
PostPosted: Sun Mar 14, 2021 9:27 pm 
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SO, to get this right the problem is with both the Plexy (whatever that is) lap and ultra laps? Do you have a chrome ultra lap, assuming your talking about the thin film type, try that if you have one.

The plastic lap is acrylic I think. I used it with a cerium oxide slurry on a few stones before with success. I also tried Tin Oxideslurry but I think that is an obsolete material. I switched to the ultra lap film since I could not make the acrylic work. The ultra lap had the same problem with large scratches appearing on some facets and not others. The scratches looked like what I would expect little chunks of stone had detached from the stone and rolled across the facet causing scratches. But I could not see any chipped edges.

The fact your implying it is more than one stone your getting one facet that will not facet seems odd to me. Diamond as a finish polish on quartz can be as troublesome as what your stating, but I have done it with success, but usually follow with cerium on a composite type lap afterwards.

This pattern of some facets repeatedly getting scratches happened on 2 separate stones from a same rough purchase. Natural Bahia Citrine, Purchased from a reliable source. The pieces could have been from the same material. I'm starting to think that this rough is just not good.

When you say "composite type lap" what do you mean, can you give me an example.

I used to be a volunteer stone cutting demonstrator at the Ontario Science Center. I have experience polishing cabs but faceting is new.


There is some Quartz that has particular phenomenon, I forget right know what it is called. Maybe you have some, just a thought.
Could you be thinking of Twinning?
Thanks for your help


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 Post subject: Re: Polishing Woes
PostPosted: Sun Mar 14, 2021 10:15 pm 
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I think the phenomenon that was mentioned with quartz polishing is referring to "herringbone" patterns? if I recall correctly this often occurs after a 3K diamond prepolish, but may occur under other circumstances too. I seem to recall that the "trick" here was not to pre-polish those facets. Going right from 600 grit to polish seemed to be the work-around I remember reading. Give that a shot and see if that helps.

I can't say I've ever run into the particular issue you describe on quartz that was not fixed by changing cutting directions, or speeds though.

It may also be possible that there is an invisible fracture on that part of the stone and causes tiny chips to come off when you polish. You may be able to cut past this(would likely require re-cutting that entire half of the stone though)

Another random thought here... are you SURE it's Quartz? if you have a material with a cleavage plane it can cause issues like you describe if the one facet sits parallel to the cleavage plane.

One other possibility here: perhaps you could modify your design a bit here to change the facet angle, or add an new tier of facets that cut away the problem facets. I've done this before when trying to recover a stone where I had a small chip when polishing one of the last facets. I changed it to be a "split mains" design and only had to cut/polish one more tier of facets to fix everything.


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 Post subject: Re: Polishing Woes
PostPosted: Mon Mar 15, 2021 2:15 am 
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That was what I was forgetting, "Twinning". Composite laps are like the Dark side, matrix, diamatrix, and many of the no polish needed as the polish is built in like light side, creamway etc.
If it were me right now in your situation and based just on your comments, I would make the copper lap an 8k prepolish lap. The tin alloy if new make it a 50k or 60k. Both with diamond polish powder, or paste stick whatever you plan to use for diamond polish. Repolish the stones with the 8k and then follow with the plexy charged with cerium, slightly to the dryer side and very low speed almost to where you think the the stone is grabbing the lap, just a small spritz of water is all that is needed to keep it slightly moist. Does this Plex have a shiny surface?

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 Post subject: Re: Polishing Woes
PostPosted: Wed Mar 17, 2021 12:21 pm 
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Two thoughts from my own experiences cutting lots of Bahia amethyst and citrine...

The plexiglass laps don't always do so well in their original polished state. Roughen the surface with some coarse sandpaper (I use 40 grit flint paper on a flat counter, "swirl" the lap on it), then clean well and smooth a touch with a crystal before applying polish.

I found that when quartz wanted to show scratches or odd polish patterns "no matter what I did", adding about 10-20% green chrome oxide powder to the cerium oxide powder before making the slurry worked wonders...

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 Post subject: Re: Polishing Woes
PostPosted: Wed Mar 17, 2021 6:47 pm 
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Sounds to me hat it may e a problem with the stone having microscopic inclusion that create problems in certain polishing directions.

Put it under a good quality microscope with darkfield illumination. If this does turn out to be the problem try diamond on a hard lap to polish those facets.


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 Post subject: Re: Polishing Woes
PostPosted: Thu Mar 18, 2021 4:16 pm 
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1bwana1 wrote:
Sounds to me hat it may e a problem with the stone having microscopic inclusion that create problems in certain polishing directions.

Put it under a good quality microscope with darkfield illumination. If this does turn out to be the problem try diamond on a hard lap to polish those facets.

I did this and did not see anything particularly obvious. There are very tiny bits and pieces in there though, so that's a possibility. I also tried crossed polar, and maybe, just maybe there is some twinning. It's a bit tricky with the stone still on the dop, and the reflection and not completely polished.
In the meantime I prepared and cut another citrine from another lot. Same pattern and laps so very similar conditions. It polished in seconds flat.

I think I will call this stone Experience, and move on.


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 Post subject: Re: Polishing Woes
PostPosted: Thu Mar 18, 2021 4:48 pm 
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Give the diamond/hard lap a try on that facet. It will likely fix the issue for you.


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 Post subject: Re: Polishing Woes
PostPosted: Fri Mar 19, 2021 7:26 pm 
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1bwana1 wrote:
Give the diamond/hard lap a try on that facet. It will likely fix the issue for you.

I've never used a diamond lap. I have diamond paste and a tin allow lap as well as a copper lap, but the instructions online to charge the lap, and then use them, are all over the map. Score, don't score, use water, never use water, fast, no very slow, etc.

Any reliable reference?

Another question, if the lap gets contaminated can it be cleaned.


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 Post subject: Re: Polishing Woes
PostPosted: Fri Mar 19, 2021 8:07 pm 
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Curious-George wrote:
1bwana1 wrote:
Give the diamond/hard lap a try on that facet. It will likely fix the issue for you.

I've never used a diamond lap. I have diamond paste and a tin allow lap as well as a copper lap, but the instructions online to charge the lap, and then use them, are all over the map. Score, don't score, use water, never use water, fast, no very slow, etc.

Any reliable reference?

Another question, if the lap gets contaminated can it be cleaned.


Your just to Curious George, Like Nike Just doIT already!

Go here works for any metal lap http://www.battlap.com/

These steps are not that hard to follow:
Quote:
Charging a New Metal Lap
Things we learn over time
Faster easier charging, for polish or prepolish grits:
>> Take a clean dry BATT™ or BA5T lap. (Or any metal Lap)
>> Wipe lightly with a WD-40 dampened tissue.(or any lubricant you want, or paper towel)
>> Wipe nearly dry.
>> Rub on with a clean fingertip a thin 'monolayer' of your chosen diamond powder, such as 50K for polish or 3K for prepolish. (Or use a Q-Tip if you want, a small paint brush)
>> Use a test piece of corundum to set the diamond powder...OR just start polishing. (This is charging the lap, the method to embed the diamond particles into the surface of the lap, or just start polishing your stone, it becomes the piece of corundum.)
>> When polish rate slows down, wipe off swarf and "Black Stuff" and repeat previous steps.
SWARF IS YOUR ENEMY! IT CAUSES DRAG, SCRATCHING, and HEATING!-Especially on CZ and garnets!(Remember, ALWAYS sweep the lap)


Watch the video on the same Gearloose page. http://www.battlap.com/

A simple Youtube search "Charging a metal facet lap"
results in several reliable videos, UltraTecUsa, John Baily, MoreGems. Charging a lap is as easy as buttering your toast or pouring syrup on a pancake.

Depends on the contamination, it may be able to be simply cleaned, or it may need resurfaced.

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