All of the calcite pigment layers contained significant amounts of light red-brown particles ranging up to 100 pm, and studies showed that they were all iron-stained ortho-quartzites.
Regardless of whether whewellite in pigment layers has occurred as a result of alteration processes involving local biological activity or atmospheric oxalates, the resulting changes appear to preserve the art in terms of the retention of the shape and style of the images.
Until now, the analysis had remained qualitative, because all the pigment layers
were considered simultaneously New technical advances and software have now allowed us to resolve cross-sections of the layers and to quantitatively analyze the composition and thickness of the individual pigment layers
Although O'Donoghue addressed his Passion works avowedly disinterested in their religious content, the subject matter of the Passion--seen as journey, metamorphosis, sacrifice--well suited this painter's language: the gradual building up in rich pigment layers
toward delineation of form, and the tension in reconciling the abstract values of his very sensual large colour fields (he studied Rothko and Newman) with his interest in the conceptual potential inherent in the human image.
Detail was created laboriously with fine brushes of hair from live squirrels, luster achieved from burnishing the surface, which also bonded pigment layers
to the support (2).