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 Post subject: Are Americans the only ones cutting pavilion first?
PostPosted: Fri Aug 18, 2017 9:13 pm 
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It's just occurred to me that in all my travels and conversations, I've never met anyone who isn't American or cutting on an American style machine to start with the pavilion. Is this true and if so when did Americans start cutting this way?

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 Post subject: Re: Are Americans the only ones cutting pavilion first?
PostPosted: Sat Aug 19, 2017 2:33 am 
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It's typically the way you are taught here in Australia. I'm not sure that I've ever actually done a crown first.


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 Post subject: Re: Are Americans the only ones cutting pavilion first?
PostPosted: Sat Aug 19, 2017 3:31 am 
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I always cut pavilion first and don't understand the benefit in cutting crown first. Cutting the crown last allows the crown to be dropped if your running out of room, without greatly sacrificing the performance of the stone. Try that with the pavilion and you may exceed the critical angle, potentially causing the stone to window.

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 Post subject: Re: Are Americans the only ones cutting pavilion first?
PostPosted: Sat Aug 19, 2017 5:07 am 
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Hi Justin,
sounds very strange to me,since i've never met anyone who would Cut the crown first, be it in Sri Lanka,India, Europe as well as the few cutters i know in Thailand.As mentioned before,there is nothing to win in crown first although there might be a rare case when orienting for a nice inclusion or zoning etc. you might want to show up.
best wishes
Gemse


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 Post subject: Re: Are Americans the only ones cutting pavilion first?
PostPosted: Sat Aug 19, 2017 7:19 am 
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I learnt to do pavillion first - but at first that's just because the book told me to do it that way back in January...

For an optical perspective it's obvious to do the pavillion first, because I have much less room to freestyle the angles on that side; crown can easily be cut with lower angles if required (or higher). Play around with pavillion angles like that and things can go very wrong. So if it's 'precision' cut for optical performance, the pavillion first makes much more sense.

Is there an advantage in cutting the crown first if the goal is primarily weight retention? Maybe cut the crown to have an aesthetically pleasing look (just facet layout), or just uniform look stone to stone, and then cut the pavillion to maximize weight retention? Pretty clearly the optical performance would likely suffer, by if that isn't the driving goal then the pavillion bulge/curve etc can be adjusted more easily if it's cut last maybe?


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 Post subject: Re: Are Americans the only ones cutting pavilion first?
PostPosted: Sat Aug 19, 2017 12:07 pm 
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Swiss cutter cut table first. The Germans I've seen on traditional machines cut table first. I took a class on traditional Thai cutting a few weeks ago and the woman cut crown first. I suspect the traditional French was is similar to Germans. I don't cut crown first because to me it doesn't make sense. My girlfriend, an ex cutter for the Swiss industry tells me crown first is for getting maximum yield of weight and because the top of the stone is more important than the bottom and has to be perfect compared to the pavilion. The pavilion can be hidden and the crown can't. To me that still doesn't make sense and we have weekly battles about this topic

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 Post subject: Re: Are Americans the only ones cutting pavilion first?
PostPosted: Sat Aug 19, 2017 12:12 pm 
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I think you've found the reason. Heavier and shinier brings more money, especially if it's not shown beside a well-cut stone. Some expert cutters, by the way, do cut and polish the table first, then dop to it and cut the pavilion.


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 Post subject: Re: Are Americans the only ones cutting pavilion first?
PostPosted: Sat Aug 19, 2017 1:54 pm 
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I always cut the table first to establish the reference surface. I then decide if I want to cut the crown or the pavilion. I don't think it matters if you have a plan and preform in accordance with your plan.

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 Post subject: Re: Are Americans the only ones cutting pavilion first?
PostPosted: Sat Aug 19, 2017 6:19 pm 
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I would consider the pavilion the most important part since it is entirely responsable for the effect we see in a properly faceted gem, if it's incorrect we have a fisheye. By what you're saying, it sounds like cutting pavilion first is mostly something done in English-speaking countries :?

As noted by others here, if you have mis-judged how much material you have, the crown is usually more forgiving as you can lower the angles to accommodate by a degree not possible with the pavilion.

Depends what material you're cutting as well - while things have an optimum culet angle, I could get away with lowering the pavilion angles a little for say, a zircon. Try doing it to the same degree with an amethyst and you will fisheye it.

Like Tom says, it probably doesn't really matter as long as you've inspected and planned carefully and know what you're doing.


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 Post subject: Re: Are Americans the only ones cutting pavilion first?
PostPosted: Sat Aug 19, 2017 8:02 pm 
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My first 8 or 10 stones were taught to me by a Slovakian gentleman and all were cut pavilion first. He learned the craft while living in Africa if that helps


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 Post subject: Re: Are Americans the only ones cutting pavilion first?
PostPosted: Sun Aug 20, 2017 10:54 am 
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Justin, there are two very strong schools of thought, each completely different.

For "traditional" cutting, the goal is to absolutely maximize yield, and there isn't necessarily a flawless rigid adherence to optics or angle recommendations. If you cut the table and/or crown first, and make those look decent, you can fudge the crap out of the pavilion. Big bellies, way long keels, etc; since there's no real stigma against (some amount of) windowing in traditional cutting styles, you can cut a shallow crown and then just maximize your yield in the pavilion. Also, for the average consumer who doesn't know shit about gems, they'd never notice the difference between traditional and precision cutting unless you showed them the two stones side by side.

In precision cutting, the goal is to maximize optics, even if that's at the expense of yield. Since the pavilion has a significantly greater contribution to optical performance of the finished stone, that's cut first, to ensure that you actually get the optical performance you want - the crown can then be scaled up or down to accommodate for how much rough you have left.

Does that make sense?


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 Post subject: Re: Are Americans the only ones cutting pavilion first?
PostPosted: Tue Aug 22, 2017 6:38 pm 
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for decades, I have cut the pavilion first by dopping to a finished polished table. The table makes a good window to look inside the stone for flaws, etc., and is usually the worst facet to polish, so it makes sense to me.

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 Post subject: Re: Are Americans the only ones cutting pavilion first?
PostPosted: Tue Aug 22, 2017 11:01 pm 
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Yes thanks everyone I understand and knew most of this. I'm wondering when did this shift happen. Faceting machines were in the States by the 1890's and being mass produced by the 1940s. From what I've learned so far, most of the American knowledge and wisdom was self taught because the earliest faceting books in the states are essentially a collection of this experimental wisdom, very different that the handed down traditions of old Europe. Do you think in the American pioneering days of faceting, it occurred to someone in North America that cutting pavilion first made more sense? And since then everyone cutting in an American style has learned this way?

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 Post subject: Re: Are Americans the only ones cutting pavilion first?
PostPosted: Wed Aug 23, 2017 12:39 pm 
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justinkprim wrote:
Yes thanks everyone I understand and knew most of this. I'm wondering when did this shift happen. Faceting machines were in the States by the 1890's and being mass produced by the 1940s. From what I've learned so far, most of the American knowledge and wisdom was self taught because the earliest faceting books in the states are essentially a collection of this experimental wisdom, very different that the handed down traditions of old Europe. Do you think in the American pioneering days of faceting, it occurred to someone in North America that cutting pavilion first made more sense? And since then everyone cutting in an American style has learned this way?


I don't know of any manufacturer in the U.S. who "mass produced" faceting machines. Faceting machines are manufactured in small lots, not hundreds or thousands.
I don't think any cultural belief exists that cutting the pavilion must be done first.

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 Post subject: Re: Are Americans the only ones cutting pavilion first?
PostPosted: Wed Aug 23, 2017 12:46 pm 
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There is no cultural belief that Gravity sucks downward, either. It just does.

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