Methods and techniques

Nanomachining with a focused ion beam (FIB) - Back

Nanomachining is a fairly new method of preparing paint samples for Transmission Electron Microscopy (TEM). This technique involves a focused ion beam (FIB). An ion is an atom or molecule which has an electrical charge because of the electrons in it. A beam of ions can be used to carve out a paint sample with great precision. This enables much greater control of the exact location from which a paint sample is taken, as well as of the thickness of the section, which can be controlled to within a couple of nanometres (a nanometre is one-millionth of a millimetre). Nanomachining avoids problems that can accompany traditional methods of preparation, such as crumbling of the paint sample. This technique reveals details of the morphology (form), chemical structure and composition of pigments and binders in the paint at a nearly atomic level.

The accompanying photo is a FIB section of the original paint sample from Van Gogh’s Bridge in the rain (1887). It was prepared from a cross-section of the original sample from the ground layer of Bridge in the rain. In the first photo (an SEM micrograph), the place from which the cross-section was taken is circled. The second photo, made with TEM, shows the entire section. The third photo is a TEM image of the area circled in the second photo, with a high concentration of the pigment animal black.