What causes the "crushed ice" look?

[Garry H (Cut Nut)]

David it is much simpler.
The stones in the lower right have opposing pavilion main facets (across the short axis) and when you look in through the table the ray goes out through the table back and hits you in the head (BAM).
The stone on the upper right does not have opposing pavilion mains, so this style of cutting stops that (and creates smaller virtual facets = more crushed ice).

For the 1,000th time, take a piece of copy paper, poke a pen sized peep hole in the center, and you will see the bowtie goes away when you peek at the marquise pear or oval. Cut the paper smaller and smaller until your head begins to appear and (not being bright) the bow tie will appear and get worse as the paper gets smaller.

 

[Rockdiamond]

David it is much simpler.
The stones in the lower right have opposing pavilion main facets (across the short axis) and when you look in through the table the ray goes out through the table back and hits you in the head (BAM).
The stone on the upper right does not have opposing pavilion mains, so this style of cutting stops that (and creates smaller virtual facets = more crushed ice).

For the 1,000th time, take a piece of copy paper, poke a pen sized peep hole in the center, and you will see the bowtie goes away when you peek at the marquise pear or oval. Cut the paper smaller and smaller until your head begins to appear and (not being bright) the bow tie will appear and get worse as the paper gets smaller.

HI All,
Garry, I tried your experiment.
It did not work- for on thing, it's impossible to see anything clearly through a little hole in a piece of paper- I can't focus properly on the diamond with one eye.
But when I brought the diamond very close, and could see it, the bowtie was still there.
The whole point is kind of ridiculous anyway- either we need to have people with no heads looking at the diamonds, or they need to walk around with pieces of paper to alleviate the bow tie, if that actually worked, which it does not.
The Bow tie is a part of the cut.

The facet designs I showed above neither eliminate, or create bow ties in every case. Even the facet design on the upper right- without opposing pavilion mains will sometimes have a bow tie. There are other factors, such as pavilion/crown angle that come into play- but the difference in facet size seems to be a large factor..

 

[Garry H (Cut Nut)]

David it is much simpler.
The stones in the lower right have opposing pavilion main facets (across the short axis) and when you look in through the table the ray goes out through the table back and hits you in the head (BAM).
The stone on the upper right does not have opposing pavilion mains, so this style of cutting stops that (and creates smaller virtual facets = more crushed ice).

For the 1,000th time, take a piece of copy paper, poke a pen sized peep hole in the center, and you will see the bowtie goes away when you peek at the marquise pear or oval. Cut the paper smaller and smaller until your head begins to appear and (not being bright) the bow tie will appear and get worse as the paper gets smaller.

HI All,
Garry, I tried your experiment.
It did not work- for on thing, it's impossible to see anything clearly through a little hole in a piece of paper- I can't focus properly on the diamond with one eye.
But when I brought the diamond very close, and could see it, the bowtie was still there.
The whole point is kind of ridiculous anyway- either we need to have people with no heads looking at the diamonds, or they need to walk around with pieces of paper to alleviate the bow tie, if that actually worked, which it does not.
The Bow tie is a part of the cut.

The facet designs I showed above neither eliminate, or create bow ties in every case. Even the facet design on the upper right- without opposing pavilion mains will sometimes have a bow tie. There are other factors, such as pavilion/crown angle that come into play- but the difference in facet size seems to be a large factor..

Want to try this experiment again RD and see if you can see what everyone else does?
And in your very first photo - note that the part of the stone that would be blue in ASET is showing your hand (the pink) and it is the dark zone area on each side of the stone.

 

[Rockdiamond]

\
Here's the aset for the diamond I used as an example in my first post in this thread. There is indeed a small amount of blue in the aset.
When holding the stone perfectly still there are small dark zones at 3 and 9 o'clock- but they disappear with even a slight tilt.

Garry- in terms of experiments and what everyone sees......What is the point of the experiment?
If a stone has a bowtie, and it's visible when looked at by a person- what value do we get from verification that obstruction is causing this as opposed to any other cause of a dark zone?

 

[Garry H (Cut Nut)]

\
Here's the aset for the diamond I used as an example in my first post in this thread. There is indeed a small amount of blue in the aset.
When holding the stone perfectly still there are small dark zones at 3 and 9 o'clock- but they disappear with even a slight tilt.

Garry- in terms of experiments and what everyone sees......What is the point of the experiment?
If a stone has a bowtie, and it's visible when looked at by a person- what value do we get from verification that obstruction is causing this as opposed to any other cause of a dark zone?

Just one thing - Knowledge.

That is why consumers come here, for helpful expert knowledge.

e.g. I predicted the blue in the zone where your pink hand shows up. That dark zone will go away when you peek thru a hole in a piece of copy paper.

 

[Rockdiamond]

We have an entirely different approach Garry. Which, in itself is educational. With regards to obstruction versus leakage etc: I don't think experiments like this add a positive educational experience.
If a stone has dark zones, that's important. If we need to put on a mask to eliminate the dark zones, it's totally irrelevant to most people looking to learn what they need to for a purchase.

Trying to read aset on stones like this seems to be more frustrating than informational for people looking to learn about fancy shapes, and buy one.

 

[Garry H (Cut Nut)]

We have an entirely different approach Garry. Which, in itself is educational. With regards to obstruction versus leakage etc: I don't think experiments like this add a positive educational experience.
If a stone has dark zones, that's important. If we need to put on a mask to eliminate the dark zones, it's totally irrelevant to most people looking to learn what they need to for a purchase.

Trying to read aset on stones like this seems to be more frustrating than informational for people looking to learn about fancy shapes, and buy one.

I thought it might be easier to educate the vendors so they can buy better. But I can only take a horse to water. It really is much easier to educate the enthusiast consumers to advise others. Shame really.

 

[Rockdiamond]

It would be a shame if every vendor and cutter was going for the same look.
What you call education Garry, I call your opinion.

From what have seen first hand of aset and crushed ice stones, the aset is not providing any meaningful info to me, as a buyer. The only way to correlate anything the aset shows us is to look at the actual stone- which is how I decide if I like it- by looking at it. The aset results are not consistent in a way that's helpful.

If the aset is not providing me with anything meaningful even after I've looked at the stone first hand, I feel doubly that it won't help consumers.

 

[ChunkyCushionLover]

We have an entirely different approach Garry. Which, in itself is educational. With regards to obstruction versus leakage etc: I don't think experiments like this add a positive educational experience.
If a stone has dark zones, that's important. If we need to put on a mask to eliminate the dark zones, it's totally irrelevant to most people looking to learn what they need to for a purchase.

Trying to read aset on stones like this seems to be more frustrating than informational for people looking to learn about fancy shapes, and buy one.

I thought it might be easier to educate the vendors so they can buy better. But I can only take a horse to water. It really is much easier to educate the enthusiast consumers to advise others. Shame really.

Garry I beleive some vendors(probably a LOT of vendors) would rather call all cushions beautiful and downplay the differences. I'd like to say their sales of cushions depends on doing this.

One cushion cut from 3 Carats of rough.
The other from 2.6 Carats of Rough.

Both of them yield a 1 carat cushion and obviously the price per carat fo the vendor to purchase each is different between the two.
Vendor sells them both as equally beautiful, I wonder which one this vendor makes a higher margin on?

Is it a personal preference or is one side brighter than the other with greater potential for fire?

http://www.youtube.com/watch?v=vh0ad6dsDRk&feature=channel
http://www.youtube.com/watch?v=4UuzoMQl6Oc&feature=channel

 

[Rockdiamond]

Your yield projections are seriously off.
Each stone presents opportunities for the cutter.
Each possibility has it's cost.
In some cases there are far more limited possibilities.
So, it's not always possible to cut an 8main cushion brilliant from the same rough that might be used to cut a cushion modified brilliant.
Then, there are cutters specializing in utilizing rough other cutters can't, or won't use.

I don't think all cushions are beautiful.

 

[ChunkyCushionLover]

Here is another video.

http://www.youtube.com/watch?v=dQNw426b1k4&feature=channel

Spread and Weight Retention Versus Brightness & Fire

All diamonds simulated from sarin scans and Diamcalc.
They all use the same lighting, same tilt, same observer, same full environment and all normalized to 1 Ct.

Ugh almost time to fast