Start Strengths and limitations of radiocarbon dating

Strengths and limitations of radiocarbon dating

Instrumental techniques for the analysis of component materials - Scanning electron microscopy (SEM); electron microscopy with x-ray analysis (SEM/EDX); and x-ray diffraction (XRD) SEM high resolution images of the surface of samples with magnification of up to 100,000x show the structure of the mortar.

Changes are usually made only where the existing materials have been shown to be inappropriate.

In recent decades, specialists involved in the conservation and repair of historic buildings have become increasingly concerned by the damage caused by the use of certain types of mortar on historic brick and stonework, and by the use of ordinary Portland cement in particular.

Photography is useful for documentation of condition.

Light microscopy - Binocular microscopy; polarised light microscopy; thin sections The binocular microscope equipped with incident and transmitted tungsten light, with the potential for observation of samples in cross-polars, allows determination of the mineralogy and distribution of components and their interrelationship.

Analysis is carried out with differing goals, from a simple colour match to ensure a sympathetic 'matching' repair mix, investigative assessments and performance evaluations, to academic studies that attempt to determine the precise reasons for the remarkable durability of ancient mortars.

Many analytical techniques are being employed, each with particular strengths and limitations.

The procedures pioneered by Ian Constantinides and others, based as so much was (and still is), on John and Nicola Ashurst's excellent have been replaced by various more sophisticated techniques.

Many individuals, companies, laboratories, and universities are now offering the service, and much research is being undertaken.

In some cases the hydraulic component is being assessed on the insoluble 'fines' proportion.

This is meaningless, as in the vast majority of cases where the proportion of 'fines' is high, the mortar includes unwashed clayey aggregates.

Where historic buildings are concerned, repairs should be carried out using materials and techniques which match those used originally as closely as possible.