1. turn on the power and turn on the instrument.
2. cleaning gems and prisms with alcohol.
3. point a drop of contact liquid on the refractometer prism (about 2mm in diameter), and use sodium light to illuminate the shadow boundary of the oil.
The 4. biggest gem table into the prism, immersion to form good contact between the gem and the optical prism.
5. eyes close to the eyepiece, observe the shadows and bright areas, and read the readings. Keep the decimal point third.
6. turn stones in order 360 degrees, experienced stones can rotate 0 degrees, 45 degrees, 90 degrees for observation and reading.
The 7. test is completed, the gem to nudge metal table, remove the stones.
8. cleaning gems and prisms.