Cling film is commonly encountered in forensic investigations as a wrapping for drugs of abuse. The evidential value of a match between a known and a questioned piece of cling film is directly related to the level of the chemical variation both within and between samples. However, little is known about the chemical variation in cling film. To address this, attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) was used to quantitatively assess the chemical variation in food grade low-density polyethylene (LDPE) cling film. Following acquisition of full scan IR spectra between 4000 and 650 cm⁻¹, a spectral region of potential discrimination between 1560 and 1200 cm⁻¹ was identified. The complex series of weak, overlapping absorption bands in this region were deconvoluted and peaks fitted. Bivariate plots comparing each pair of normalised peak areas showed significant overlap of the data points for the different samples, indicating no between-sample chemical variation. Further, the same plots demonstrated that the extent of within-sample chemical variation was at least as great as that between samples. Thus, in the sample set evaluated in this study, it was not possible to discriminate between food grade LDPE cling films using ATR-FTIR spectroscopy due to a lack of quantifiable chemical variation. The study therefore highlights the possibility of false positive matches in the analysis of LDPE cling films and provides a methodology to evaluate the extent of chemical variation in a relevant reference population prior to undertaking casework.

Pigments from paint palettes and a grindstone excavated from the pharaonic town of Amara West (c. 1300–1050 BCE), which lies between the Second and Third Cataracts of the Nile, were examined using polarized light microscopy, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction, and scanning electron microscopy with energy dispersive X-ray spectroscopy. Most of the pigments were consistent with the typical ancient Egyptian palette, but the greens and some blues were unusual. Two types of green pigment were identified, chlorite (varieties clinochlore and penninite) and copper chloride hydroxide (atacamite type). The former constitutes a type of green earth which has only rarely been identified in pharaonic Egyptian contexts and may be more widespread than is currently reported. The majority of the blue pigment samples were Egyptian blue, but some were found to be a blue earth, the main component of which being sodic amphibole riebeckite. The use of this mineral as a pigment has not previously been reported in any Nile Valley context. These results prompt questions around local and potentially indigenous practices within an ancient colonial context, and highlight avenues for future research.

Prismatic lead white was first described by Walter C. McCrone in 1983 when it was identified via polarised light microscopy in three paintings by Edouard Manet. It is characterised by crystals in the shape of bullets or pills (i.e. prism-shaped, hence ‘prismatic lead white’). McCrone attributed the formation of these crystals, morphologically distinct from those of ‘normal’ lead white, to processing conditions characteristic of precipitated lead white. These ‘prismatic’ crystals have subsequently been identified as cerussite (orthorhombic lead carbonate, PbCO₃). Their presence has been tentatively used to date artworks painted from the nineteenth century onwards. The article will show, through reproducing historic pigment recipes of post-treatments, that prismatic lead white can also be formed in the stack lead white process and so its presence should not be used as a criterion for dating. This article investigates the formation of these prismatic crystals in the context of the manufacture and history of lead white.