Diamond Evaluation - What Lighting Do You Use?

[TooMuchInformation]

Quick question for all the appraisers and such on this list...

When you''re appraising a stone, what light do you find works best to view the stone under, where did you get your light, and is it overhead, or an adjustable light on an arm of some sort?

I''m starting to get sick of pulling lamps off of desks and using the loupe in the bathroom and such other places with "good" lighting.

 

[Garry H (Cut Nut)]

Spot light in stair well for fire, near counter for general, office kitchen style fluoro's, near window, under bed with torch, in conservatory with blinds up and down too, cafe's and everywhere except direct sunlight

Not much help is it?

 

[mdx]

Diamonds are usually graded in a purpose made “light box” fitted with day light tubes D55-65. (not sure of the USA specs) One tube (switchable) would be normal daylight and another would be free of UV so as not to stimulate fluorescence. The light box creates a working area of uniform white cold light not affected by reflections from the environment.

For home use you can purchase day light tubes in standard sizes from you local gemological supplier. Try setting up your lamp in a room with white neutral white walls and ceiling.

Place the diamond and master stones 1cm apart in a folded preferably non-fluorescing paper bent 45degrees.

The stones should be laid table down on the horizontal part of the paper. View the stones perpendicular to the pavilion facets.
Move the folded paper around under the light to change the incidence of light until you find a spot with no distracting reflections.

Hope that helps

 

[Garry H (Cut Nut)]

oops

did i miss read?
Was it color grading ?
Or judging how a stone looks?

 

[TooMuchInformation]

Yeah, just for looking at a stone and finding all the inclusions and such. I've already seen the lighting devices used for color grading. Like all the other equipement, I WANT ONE.

Thanks muchly for both of your feedback, however. Reading responses is always enjoyable.

 

[Garry H (Cut Nut)]

OK
You need like a desk fluoro and hold the stone so most of the light enters the pavilion. Spot lighting is bad.

But remember that you could get yourself into trouble with a little bit of knowledge. If you default to missing inclusions (which you will if you try to grade diamonds in store lighting) then you will be unhappy.

 

[TooMuchInformation]

Good to know! I already fear the bit of knoweldge that I have, because as you said, I'm at the point to know what to do, but I don't know what I'm doing (if that makes any sense).

I'm not trying to actually grade, stones, just getting lots of experience with the loupe and trying to spot as many inclusions as I can and that sort of thing. Just trying to teach myself at the moment - I have no financial interest in my ability (or lack there of) at this time, and nor do I plan on having one for a long time.

 

[Rhino]

Hey toomuch..




It would depend upon what phenomena I wanted to observe. When we're in our store and discussing the seperate issues of brilliance, fire & scintillation I use the following lighting.




We have a 5800 degree kelvin light display and on one half of the lighting is direct lighting. On the other half we keep a diffuser plate. When I am discussing brilliance (especially with regards to white light return and the issues of contrast as measured on the Isee2) I show the client under 5800' diffuse lighting which plainly shows the phenomena of brilliance as opposed to fire/dispersion. By simply moving the diamond away from the diffuser plate and under the direct lighting immediately the diamonds change appearance. Fire & scintillation are emphasized which is dependant upon the strength/intensity of light being returned through the crown (practical observance of B'scope results). We will also observe differneces under office lighting (generally fluorescent diffuse) and my personal favorite is ambient lighting. We'll go by the front window of our store and let natural daylight fall onto the diamonds in question and the superior cut quality will always demonstrate soft rainbows and white light. You can also see the beauty aspects of optical symmetry in ambient light excellently too although cloudy day conditions really empahsize optical symmetry best IMO.

 

[strmrdr]

When I was looking at diamonds to buy one what I would do in stores with the bright spot lights is shade it with my fingers if it danced and sparkled just from the reflected light from my hand/shirt it was a better than average one.

Same thing in bright sunlight put your back to the sun and see if it dances in the shadows.

White paper is also good for making your own light block and diffusing the light.

One b&m was fairly rude about me doing this and mall store clerks looked at me like I was nuts.
Maybe they were right but I could tell a lot more about a diamond once the lights were off it.

You will be shocked how few diamonds will look good under these conditions.

Now for color without going crazy on special lights GE reveal true white lights are great :}
You will be amazed at the difference they make on colored objects and how yellow regular light bulbs make things and how blue florecent bulbs make things compared to the reveal bulbs.
I know of a couple pro photographers that are using them instead of the outrageously expensive bulbs they used to use.
They put out a nice clean white light.
Make sure to use no reflector or as pure a white one as you can find as to not add color to the light.
They really make gemstones dance.

 

[Hest88]

Funny, but I expected one of Garry's answers to be "on a sunny beach with a beer."

 

[knowverylittle]

>>When I was looking at diamonds to buy one what I would do in stores with >>the bright spot lights is shade it with my fingers if it danced and >>sparkled just from the reflected light from my hand/shirt it was a better >>than average one.
Good advice strmrdr. I am going crazy looking in stores as they all as seem to sparkle about as much under their bright lighting. FYI: I postponed the diamond until the Summer, the ring is ordered with a CZ for now. After the postings responding to my selection of three it appeared I still know too little about diamonds... so am still researching off and on until summer. FICs are staring to appeal.