Take a look at what our heritage types are made of
These four samples of Chinese heritage type are ready to be placed into a scanning electronic microscope (SEM). SEM analysis will help determine the chemical composition of the metal alloy, as well as show the types at higher magnifications.David Flynn, EM technician at the School of Chemical and Physical Sciences, puts the prepared samples into the SEM.The SEM is a kind of electron microscope that produces images of a sample by scanning it with a focused beam of electrons.The heritage type samples are examined in low vacuum, as this setting copes better with the inclusion of organic matter than high vacuum. We capture information about the samples’ surface topography as well as composition.Analytical software visually maps out the chemical composition of a sample. Each coloured layer corresponds to one chemical element – in this map, red shows carbon, green shows antimony, and light blue shows tin.The surface of a type sample transforms into an awe-inspiring moonscape at 350 times magnification.A periodic table is useful to have on hand when interpreting compositional scan images: the brightness of an area gives clues about the element’s atomic weight. The brighter an area, the heavier its atomic weight and vice versa. In our samples, bright areas show metallic materials and dark areas show organic matter. Given these samples were recovered from an onion shed, the organic debris can be anything from dust, to fertilisers, or even to a piece of insect!Scratches, pockmarks, and textures of the printing surfaces become visible even at low levels of magnification (30 times). These marks and imperfections record an impressive accumulation of use over twenty years, printing the New Zealand Chinese Grower’s Monthly Journal (1952-1972).At 3000 times magnification, this surprisingly organic-looking scan shows minute cracks in the surface oxidisation and beads of lead chloride – handle with care!
