How do GIA/AGS lab grade fluorescence stones?

[Dancing Fire]

do they use a master set of fluorescence stones like they do with color grading?

 

[Texas Leaguer]

Yes they do use masters. There are a couple of differences in the way the two labs approach reporting on fluorescence. AGS assesses from the face up direction and they use the term Negligible to include both None and Faint in the GIA lexicon. This color grading article has a section toward the bottom with a little more info.
https://www.pricescope.com/journal/ags-laboratory-color-grading-diamonds

 

[Dancing Fire]

Thanks TL.. any pics of their master set?

 

[30yearsofdiamonds]

The GIA has been using a machine that they developed themselves for use in the labs. It was calibrated to a specific master set that was already in use in the lab for many years. The majority of stones are graded for UVF on the machine. They have been using this machine for nearly 10 years if my memory serves me right. Over the years they had refined it and improved its capabilities for larger diamonds. They still do have master sets that can be used for large diamonds and discrepancies.

 

[Dancing Fire]

Any updated informations?