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 Post subject: Digital Refractometer
PostPosted: Thu Jan 05, 2017 6:10 pm 
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I'm GIA trained hemicylinder refractometer. Mine is becoming scratched. I'm considering the Gem-in-eye III digital unit to speed up things and illuminating RI liquid Is this wise? ive never used one and I'm concerned with accuracy and performance I will always have a glass unit also. Thank you


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 Post subject: Re: Digital Refractometer
PostPosted: Fri Jan 06, 2017 7:22 pm 
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Go with a another refractometer if you are going to purchase a new instrument.

You can get your hemicylindar professionally refinished or do it yourself with some cerium oxide.


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 Post subject: Re: Digital Refractometer
PostPosted: Sat Jan 07, 2017 11:04 am 
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I had the scratches taken off mine a couple years ago. http://www.gemcutting.com/
He has a holder to polish the hemisphere without taking it out of the case.

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 Post subject: Re: Digital Refractometer
PostPosted: Sun Jan 08, 2017 12:21 am 
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Thank you. I'm rather attached to my refractometer I will follow Your advice. I just liked that the digital device goes well over 1.81 and no liquid mainly because it's 90$ a bottle and I've had some moronic and expensive spills lol. Is it strange I like the smell and consider my first refractometer an old friend? Oh well


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 Post subject: Re: Digital Refractometer
PostPosted: Sun Jan 08, 2017 12:43 am 
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$90 a bottle?!? Are you using the Methylene Iodide or something else (real, toxic 1.81 RI liquid)?
You should be able to find it for a fraction of that price!


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 Post subject: Re: Digital Refractometer
PostPosted: Sun Jan 08, 2017 1:48 am 
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"Digital Refractometers" are reflectometers and mostly don't work very well.

Rather than having the unit repolished I would send it to Jeff Wildman to have a new hemicylinder put in. He charges $300.

There is an article on change in calibration by Trevor Linton in the Australian Gemologist. You can try and dig that one up for more info.


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 Post subject: Re: Digital Refractometer
PostPosted: Sun Jan 08, 2017 1:32 pm 
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Lifted from a post of yours in the past Gene:

http://www.australiangemmologist.com.au/
Volume 22, Number 10, April - June 2006
RE-SURFACING A REFRACTOMETER PRISM
Trevor Linton
Wellington Point Queensland
ABSTRACT
In this paper, the potential problems associated with repolishing the degraded soft glass surface of refractometer prisms are described. Explanations and remedies are offered for the errors that are induced in refractometer scale readings as a direct consequence of this commonly used repolishing step.


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 Post subject: Re: Digital Refractometer
PostPosted: Sun Jan 08, 2017 11:45 pm 
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Thank you I have been saving for a portalab from him. Ive only ever purchased RI liquid through GIA which is about 90$ with shipping. Being a rookie I was afraid to try other sources. what should It cost and from which sources could you recommend? thank you


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 Post subject: Re: Digital Refractometer
PostPosted: Mon Jan 09, 2017 11:44 pm 
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It has been my experience that RI liquid lasts for years.
Analogy: A pizza a year for years


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 Post subject: Re: Digital Refractometer
PostPosted: Tue Jan 10, 2017 12:47 am 
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NovaGem wrote:
Thank you I have been saving for a portalab from him. Ive only ever purchased RI liquid through GIA which is about 90$ with shipping. Being a rookie I was afraid to try other sources. what should It cost and from which sources could you recommend? thank you


It should just be Methylene Iodide with Sulfur dissolved in it, probably a saturated solution. It's not rocket science.
I haven't had to buy any yet, but last i saw, some folks were buying it in the $30-36 range or even less...
Will go through the information to see if I can find a supplier for you.


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 Post subject: Re: Digital Refractometer
PostPosted: Wed Jan 11, 2017 5:27 am 
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There is more than sulfur dissolved in it. There are two forumulations one based on Tin Oxide and one based on acetylene tetrabromide or something similarly unobtainable.

The supplier is www.cargille.com


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 Post subject: Re: Digital Refractometer
PostPosted: Wed Jan 11, 2017 1:10 pm 
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Thanks, Gene. I was trying to remember cargille, and went blank.
Excellent source.


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 Post subject: Re: Digital Refractometer
PostPosted: Thu Jan 12, 2017 10:51 am 
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The RI liquid from GIA is also from Cargille but they mark it up to ridiculous prices so you might as well go to the source if you're in the states. The shipping from Cargille is incredibly high overseas

By the way the current price from Cargille is

Item# 19160
Gem Refractometer Liquid
nD = 1.810 +/- 0.005 @ 25°C 10 grams
$57.75

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 Post subject: Re: Digital Refractometer
PostPosted: Thu Jan 12, 2017 7:33 pm 
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thank you for the info. it sounds like a better option. Veteran advice is much appreciated.


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