The epoxy was formed from two components,
these being an epoxy resin (Ciba-Geigy Araldite
LC177B) and a hardener (Ciba-Geigy Araldite
LC177). These two components were individually
degassed in a glass vacuum desiccator using a
Dynavac model rotary pump to remove entrapped
air. A Rotaflo-type stopcock was employed to
ensure that a desirable degassing rate was achieved.
The two components were added together and
mixed vigorously in a 5:1 weight ratio either with a
palette knife or in a heavy-duty mixer, depending on
the quantity that was to be mixed. To make the
composite the barytes (Commercial Mineral Ltd,
standard grade), which had an average particle size
of 63/xm, was added up to the required weight
fraction in 5 g steps while mixing continued. Once
mixing was complete with the barytes completely
incorporated, the composite was poured into a
mould, which was returned to the vacuum desiccator
so that the composite could be degassed before it
was cured. This technique ensured that no air was
trapped in the composite, which would have decreased
the X-ray attenuation.