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Author Topic: Quartz, cutting and polishing  (Read 1938 times)

RoughCreations

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Quartz, cutting and polishing
« on: May 04, 2023, 01:35:00 PM »
A bit of a rambling post - I cut a lot of quartz, mostly bigger smoky quartz. I find some parts of the process challenging, and other aspects fairly straightforward and repeatable.
I find the Darkside with CeO works for me, I have a Creamway lap, used with extra ZrO via a Battstik, however I find it polishes very slowly for me compared to CeO on a Darkside, which is contrary to how its supposed to work. I haven't tried diamond on a tin lap, pewter lap or Battlap with water, but if I get a stone that doesn't behave itself using my usual process, those methods are next on my 'to try' list.
Recently I have been cutting some 'Pixel' cuts in smoky quartz, aka opposed bar cuts. These types of cuts have a sharp keel, meaning quartz can often chip along the keel facets due to its brittle nature, especially during the polishing stage.
I found in the past that this chipping in quartz could be prevented by polishing with the leading edge of the keel facing the direction of rotation of the lap. However, the smoky quartz I am cutting at the moment (design: Andrew Brown Glitter Bar Vol. 4) refused to behave, and only stopped chipping when I polished with the keel edge parallel to the direction of rotation. My strong belief is that the quartz crystal axis orientation with respect to the cut is a factor in this chipping. This perhaps could also explain some polishing problems many people have with other non-quartz stones, and also certain facets in a given stone.
Apparently quartz is one of the few minerals that has different hardnesses in different directions (see below). It would logically follow then, that the physical process of polishing would be influenced by this anisotropic hardness property of quartz. Thoughts anyone?
RC


Graph taken from: Some Fundamentals of Mineralogy and Geochemistry
L. Bruce Railsback, Department of Geology, University of Georgia, Athens, Georgia 30602-2501 U.S.A.
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Faceting Frank

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Re: Quartz, cutting and polishing
« Reply #1 on: May 04, 2023, 08:47:06 PM »
I Don’t cut many quartz stones these days, used to cut a lot decades ago. I polish quartz using the method in AFG facet talk 246 page 11. This method is using cerium oxide powder mixed with water on a lucite lap, applied with an artists paint brush at about 250rpm. It works very well polishing quickly from a 3k diamond pre-polish on a BATT lap. Will also polish directly from a 1200 grit diamond lap. Advantages, no drip to wash all the cerium off the lap. Disadvantages, constantly having to use the brush to keep the lap wet.
Never tried cutting quartz with narrow edges or pointed facets, so have no experience with that. Thrown away all my Battsticks, cerium, 60k diamond and can’t remember the name of the other one. Blaming them for scratches, probably caused by drying out over age.
So read page 11 and give it a go.

Bucket

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Re: Quartz, cutting and polishing
« Reply #2 on: May 05, 2023, 11:10:19 AM »
These days I'm cutting a lot of quartz, I use a similar method to Frank, but I apply the cerium (white one) in a very milky mix via a dripper (2-3 drops) with a light spritz of water if the lap gets a bit dry. Speed is a very low setting. The lap is a pewter one and seem to work very well.  I've not had any real problems with chipping and I pre polish on a very well worn 1200 lap. The facets are clean and sharp and it polishes very well. I don't seem to get a lot of build up but do wash the lap on occasion. I currently have no reverse switch on my Facetron but haven't had the cause to use it. I have one to fit when I return home. Reason for this is I bought a Chinese made speed controller, without a reverse switch, before Wyatt Yaeger got Facetron up and running again. I will be getting a genuine when this one blows, which I don't expect it to last long at less than $40!
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RoughCreations

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Re: Quartz, cutting and polishing
« Reply #3 on: May 05, 2023, 12:13:13 PM »
I Don’t cut many quartz stones these days, used to cut a lot decades ago. I polish quartz using the method in AFG facet talk 246 page 11. This method is using cerium oxide powder mixed with water on a lucite lap, applied with an artists paint brush at about 250rpm. It works very well polishing quickly from a 3k diamond pre-polish on a BATT lap. Will also polish directly from a 1200 grit diamond lap. Advantages, no drip to wash all the cerium off the lap. Disadvantages, constantly having to use the brush to keep the lap wet.
Never tried cutting quartz with narrow edges or pointed facets, so have no experience with that. Thrown away all my Battsticks, cerium, 60k diamond and can’t remember the name of the other one. Blaming them for scratches, probably caused by drying out over age.
So read page 11 and give it a go.
Thanks Frank, seems like now is a good opportunity for me to join the Australian Facetors Guild.
RC
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RoughCreations

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Re: Quartz, cutting and polishing
« Reply #4 on: May 05, 2023, 12:16:52 PM »
These days I'm cutting a lot of quartz, I use a similar method to Frank, but I apply the cerium (white one) in a very milky mix via a dripper (2-3 drops) with a light spritz of water if the lap gets a bit dry. Speed is a very low setting. The lap is a pewter one and seem to work very well.  I've not had any real problems with chipping and I pre polish on a very well worn 1200 lap. The facets are clean and sharp and it polishes very well. I don't seem to get a lot of build up but do wash the lap on occasion. I currently have no reverse switch on my Facetron but haven't had the cause to use it. I have one to fit when I return home. Reason for this is I bought a Chinese made speed controller, without a reverse switch, before Wyatt Yaeger got Facetron up and running again. I will be getting a genuine when this one blows, which I don't expect it to last long at less than $40!
Sounds pretty much like the same technique as me, except substituting a pewter lap for a Darkside lap. I don't use the reverse switch on my Facetron, just use a different quadrant of the lap.
RC
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RoughCreations

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Re: Quartz, cutting and polishing
« Reply #5 on: May 05, 2023, 02:31:26 PM »
Regarding cutting big quartz stones, I read this article recently: http://ctminsoc.org.za/articles/an-unconventional-way-of-pre-forming-%E2%80%9Cdoorstops%E2%80%9D-. There are lots of other interesting articles on this site if you rummage around, too.

The author used diamond-encrusted pads to quickly preform his quartz "door stops". I found some of these pads on an Australian website, and there are also plenty on Ebay etc:

https://diamach.com.au/shop/diamond-polishing-pads-drums-sheets-and-blocks/velcro-backed/150mm/diamach-150mm-5-x-7mm-copper-bond-diamond-floor-polishing-pad-200/
These are used widely in the industry to polish granite floors or counter tops etc, so the scale of use means they are often cheaper than lapidary disks which have a much smaller user base. Has anyone tried these types of diamond pads? I am a little scared that they would be like using a jackhammer on quartz - inducing all sorts of micro-fractures, but always interested in trying a new approach.
RC
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MakkyBrown

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Re: Quartz, cutting and polishing
« Reply #6 on: May 07, 2023, 06:31:33 PM »
RC, How about giving pewter lap a go?  I'd still pre-polish with your 800 from Bert. I'm finding my Chinese resin 800 gives a good preploish or maybe a 1200 on pewter.

RoughCreations

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Re: Quartz, cutting and polishing
« Reply #7 on: May 08, 2023, 09:19:19 AM »
RC, How about giving pewter lap a go?  I'd still pre-polish with your 800 from Bert. I'm finding my Chinese resin 800 gives a good preploish or maybe a 1200 on pewter.
Yeah, OK, I would give pewter a go. Always useful to have an open mind and test another approach.
RC
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MakkyBrown

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Re: Quartz, cutting and polishing
« Reply #8 on: May 08, 2023, 07:24:53 PM »
Regarding cutting big quartz stones, I read this article recently: http://ctminsoc.org.za/articles/an-unconventional-way-of-pre-forming-%E2%80%9Cdoorstops%E2%80%9D-. There are lots of other interesting articles on this site if you rummage around, too.

The author used diamond-encrusted pads to quickly preform his quartz "door stops". I found some of these pads on an Australian website, and there are also plenty on Ebay etc:

https://diamach.com.au/shop/diamond-polishing-pads-drums-sheets-and-blocks/velcro-backed/150mm/diamach-150mm-5-x-7mm-copper-bond-diamond-floor-polishing-pad-200/
These are used widely in the industry to polish granite floors or counter tops etc, so the scale of use means they are often cheaper than lapidary disks which have a much smaller user base. Has anyone tried these types of diamond pads? I am a little scared that they would be like using a jackhammer on quartz - inducing all sorts of micro-fractures, but always interested in trying a new approach.
RC
You can get those pads cheap from china. I have 4 inch and 6or7inch, in a range of grits. I was using them to polish agates when I first started with lapidary.
MB

Bucket

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Re: Quartz, cutting and polishing
« Reply #9 on: May 08, 2023, 08:49:06 PM »
RC, just for your info the two pewter laps I have were made by one of our members by melting down mugs etc. He then milled them on a lathe and are amongst the flattest laps I have. They are thick enough to be refaced and as a result are reasonably heavy, but they work a treat. I use one for cerium and the other for 50K diamond, but only use that on rare occasions like topaz or the odd sapphire.
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Faceting Frank

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Re: Quartz, cutting and polishing
« Reply #10 on: May 12, 2023, 11:56:34 AM »
Just as a point of interest, baby oil has a refractive index of 1.45. I put some on quartz with a paint brush when preforming to check for flaws.

Ghost

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Re: Quartz, cutting and polishing
« Reply #11 on: May 12, 2023, 09:06:45 PM »
The RI of Aniseed Oil is 1.554, and I like the smell much better.

RoughCreations

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Re: Quartz, cutting and polishing
« Reply #12 on: May 14, 2023, 04:52:06 PM »
Just as a point of interest, baby oil has a refractive index of 1.45. I put some on quartz with a paint brush when preforming to check for flaws.

That's about the RI of eucalyptus oil, too.
For smoky, I like using a bright LED torch shone sideways through the stone, but viewed from above using my Optivisor. I rotate the stone slowly, and any veils, cracks or other inclusions present will reflect the light upwards and stand out nicely at a particular angle of rotation.
RC
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