I purchased a used GIA Duplex II refractometer. The hemicylinder was scratched. I had a Graduate Gemologist take a look at it for me. The report was that it’s usable but a little fuzzy. When I look into my lens, I see a black bar that rises and lowers as I move my head in an up/down motion. But I never see a green line, faded/fuzzy or not.

Here’s my dilemma: do I have the instrument looked at by another person, find somewhere to have the refractometer hemicylinder repaired, or purchase another refractometer in better shape?

Any advice would be most appreciated.


Removing Tarnish From A Refractometer Hemicylinder

I had a similar problem after buying a used GIA Duplex II refractometer for my business. The problem you’re experiencing is common and easily remedied. Because of the high lead content of the glass and subsequent softness, the surface of the refractometer hemicylinder will actually tarnish.

To remedy this, you’ll need to re-polish the hemicylinder. This is easier than it sounds. You’ll need some common supplies for lapidaries and about 15 minutes.

  • Mix a small amount of cerium oxide with distilled water to make a thick paste. (The