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Author Topic: Cutting a blue on green sapphire  (Read 7098 times)

Bluey Zarzoff

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Re: Cutting a blue on green sapphire
« Reply #15 on: April 12, 2013, 09:55:39 PM »
Cindy. About time you got on here.

Pete Brown still heat treats. Bill Hagan is getting out of it I hear.

Have been told that it is sometimes better to leave a bit of silk in the stone to prove it's natural state, as long as it is not detracting on the finished product. Like Cindy said, often, this will give the stone it's indiviluality
I started out with nothing
And still have most of it left.

-----------------------------------
Women will never be equal to men until they can walk down the street with a bald head and a beer gut, and still think they are sexy.

Lefty

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Re: Cutting a blue on green sapphire
« Reply #16 on: September 02, 2015, 01:12:15 PM »
Bit of an old thread here I know but I'm finally cutting a good sized CQ sapphire. No one has ever fully explained to me the ins and outs of on table/off table. The stone I'm cutting is blue with a rather light-coloured green cross. A little projecting bit on the bottom was yellow. I cut that off (since it couldn't have been kept an a bigger stone anyway), that faceted a very pretty little stone of about a carat.

The bigger stone is still on the dop, being cut in the on-table position as recommended to me. The blue colour is starting to show more brightly looking directly at the culet, sharp point on than I expected with the pre-polish, even with the stone still attached to the dark coloured epoxy.

I'm guessing it's easier for light coming in from around the sides to penetrate the light green colour of the cross in order to enter the stone than it would be for it to light up the stone if it had to pass through deeper blue first (which would have been the case if I had cut it off table)?

Also, how do others here approach cutting sapphire? First couple I did were a bit iffy as to the final polish. The fourth one I cut (which was the last one completed) finished very nice after cutting in the facets a normal plated #3000, pre-polishing them with #8000 on copper and then giving them a final touch up using #100 000 Blakstick on a composite ceramic lap. I'm very pleased with the end result of that combo but can any more experienced sapphire cutters tell me if there is a way they think might be faster/better?

Cheers

Bucket

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Re: Cutting a blue on green sapphire
« Reply #17 on: September 02, 2015, 02:40:52 PM »
Good questions Lefty, I'm starting my first decent sapphire (nice 6 ct yellow and green) when I get home and this info would be of great assistance.
Common sense isn't exactly common

Lefty

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Re: Cutting a blue on green sapphire
« Reply #18 on: September 02, 2015, 03:58:45 PM »
Good questions Lefty, I'm starting my first decent sapphire (nice 6 ct yellow and green) when I get home and this info would be of great assistance.

Yep, the extreme hardness seems to be about the only real issue Bucket. Someone told me that they cut the facets in on #8000 - when I tried that I found it excruciatingly slow regardless of how much diamond/lubricant were on the lap and also very quiet and difficult to hear when cutting stopped.

However, after cutting in the facets on a plated #3000 (which seems just as quick with sapphire as anything else) I've found that the #8000 on copper puts a very nice pre-polish on the surface, eliminating any orange peeling without difficulty. The final #100 000 polish is then mostly just a matter of a fairly quick touch up.

But I'd like to hear from others as to how they tackle sapphire.

drft_er

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Re: Cutting a blue on green sapphire
« Reply #19 on: February 10, 2016, 06:38:25 PM »
Gday Lefty,
Was trolling for posts about my current project and found this one.
I have not had much problems with sapphire yes a stone can vary in "hardness" especially parties. I think cutting and polishing is like picking fishing lures what works for me might not suit you.
Personally I use 1200 if I have a lot to remove then I have a worn 1200 i use to cut  to meets, if I notice stone has softer areas I cut to depth using meet point indicator ( dial gauge). I then use 3000 copper for pre polish usually takes only 3 to 4 swipes and  tidy any small errors
Then 100000 on a Horst special lap - This is a white metal lap made by Horst Ricker at rubyvale harder than normal type metal excellent on those hard stones again usually only takes a couple of swipes for great polish.
I am not a fan of using smaller grits eg 3000 to cut to meets as I have had too many dropped with wax let go from heat trying to cut with to find a grit. Also speed is key when limited time available.

Cheers
I Guess Ill keep Diggin or Fishing Hmmm or Golfing. There's just not enough hours in a day!!

Lefty

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Re: Cutting a blue on green sapphire
« Reply #20 on: February 11, 2016, 06:41:33 AM »
Hey drft_er, I gave up using wax for dopping after too many mishaps which forced stones to be recut altogether. The black faceting wax I was using liquefies very suddenly at seemingly relatively low temperatures, is very brittle and only needs to be waved over an open bottle of metho and the fumes alone cause it to start breaking down.

I now use epoxy for most things. It's slower but I've only ever had one stone come off the dop (I slipped and dropped) and never had one move due to heat while polishing. I started using the red-brown wax I used for cabbing when I first joined the club - it's tougher and less brittle than the black stuff, will absorb more heat before it begins to soften and is largely unaffected by alcohol solvents. It obviously has a different chemistry altogether and I don't think I ever had a cab let go while using it. But I've had so many problems with wax previously that I still don't trust it enough to use it on anything of monetary or sentimental value and never on anything belonging to someone else.

The advantages of wax are that you can start work in literally minutes and if the rough/preform turns out to be not oriented the exact way you thought it was when you go to start, just warm up the dop and re-orient, can't do that with epoxy obviously. But after leaving overnight, epoxy is stong and I trust the bond much more than I trust wax.

I was told a little while ago that my problem was not the wax, it was the sapphire - they are excellent conductors of heat and transfer any heat buildup from friction straight to whatever is holding the stone on. Epoxy is more heat resistant.

Mal Johnson from VJ was telling me about white metal laps but I never got round to getting one.

Cheers

Navneetgems

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Re: Cutting a blue on green sapphire
« Reply #21 on: March 24, 2020, 11:57:11 PM »
Thank you all for this amazing idea on sapphires. great advices and really have good expertise here.
Navneet Agarwal
Navneet Gems

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