Carbon Coating Thickness

Dr. Norman Charnley, Department of Earth Sciences, University of Oxford

Procedure:

Using a piece of polished brass, they give a table of carbon coating thickness (in Angstroms) against interference colour:

150 - Orange
200 - Indigo red
250 - Blue
300 - Bluish green
350 - Greenish blue
400 - Pale Green
450 - Silver Gold

We have successfully used this technique in our laboratory for the last 20 years or so, and it's quite easy to judge the thickness to within about 25 Angstroms.

References

D.M.Kerrick, L.B.Eminhizer & J.F.Villaume, "The role of carbon film thickness in electron microprobe analysis", American Mineralogist (1973), 58, 920-925