iron bolt; one image produced by secondary electrons (SEI) and the other by
back-scattered electrons.
Energy Dispersive X-ray Spectroscopy and Wavelength Dispersive Spec-
troscopy. Another useful signal collected from interactions of the primary
beam with the sample surface are the X-rays generated within the sample.
These can be analyzed both as a function of their energy (EDS) or their wave-
length (WDS). EDS collects a range of energy signals, typically in the
0–10 KeV or 0–20 KeV range with a multi-channel SiLi detector. Each elem-
ent in the sample produces a characteristic energy that can be collected and
displayed on a monitor (see Figure 7).
EDS is a fast technique that can produce qualitative elemental informa-
tion within a few minutes. Although the computer will process results in a
Methods in Conservation 21
(a)(b)Figure 6Scanning electron micrograph of a corroded iron bolt (a) SEI and
(b) back-scattered electron image