Art Conservation and Turkey Red Dyeing

In studies of material culture, one must first determine the “material.” In textiles, these materials include fibers, fabrics, dyes, and finishes. As a conservation scientist at the Harvard Art Museums, Dr. Julie H. Wertz synthesizes chemistry and historical knowledge to answer the question “what is it made of?” Her research specialty is turkey red dyeing, specifically in Glasgow where it occurred from 1785 to 1936

Authenticating Turkey Red Textiles through Material Investigations by FTIR and UHPLC

Nineteenth-century Turkey red, a cotton textile dyed by a peculiar and unique process, is found in many collections around the world. It was known for its bright colour and remarkable fastness to light exposure and washing. Light fading is a significant concern in the display of historical textiles, and understanding more about the properties of these objects may increase the accessibility of collections. This research explored the identification of historical Turkey red through non-invasive Fourier transform infrared (FTIR) spectroscopy to detect the presence of oil – a necessary step in the process – on the fibres. Around 1869, Turkey red dyers began to transition from using madder and garancine to synthetic alizarin, which was investigated through ultra-high-performance liquid chromatography (UHPLC). The chemical profiles of 19th-century samples and references of known dye source were used to predict whether Turkey red of unknown date was dyed with natural or synthetic dye

How do first-year engineering students experience ambiguity in engineering design problems: The development of a self-report instrument

Citation: Dringenberg, E., & Wertz, R. E. H. (2016). How do first-year engineering students experience ambiguity in engineering design problems: The development of a self-report instrument.Design is widely recognized as a keystone of engineering practice. Within the context of engineering education, design has been categorized as a type of ill-structured problem solving that is crucial for engineering students to engage with. Improving undergraduate engineering education requires a better understanding of the ways in which students experience ill-structured problems in the form of engineering design. With special attention to the experiences of first-year engineering students, prior exploratory work identified two critical thresholds that distinguished students' ways of experiencing design as less or more comprehensive: accepting ambiguity and recognizing the value of multiple perspectives. The goal of current (work-in-progress) research is to develop and pilot a self-report instrument to assess students' relation to these two thresholds at the completion of an ill-structured design project within the context of undergraduate engineering education. The specific research questions addressed in this study are 1) if the piloted self-report instrument can be used to identify discrete constructs, and 2) how these constructs align with prior qualitative research findings. The objective of this study was addressed using a quantitative exploratory research design. Items for the self-report Likert-scaled instrument were designed to distinguish student experience that either accept or reject the presence of ambiguity and the value of multiple perspectives. The instrument was disseminated to a total of 214 first-year engineering students. Exploratory factor analysis was used to identify the constructs that emerge from the self-report data, and these constructs were checked for alignment with the previously identified thresholds. The results of this investigation will be used to help advance progress towards an easily administered instrument able to assist engineering educators with the identification of students in need of intervention or explicit instruction related to critical aspects of learning engineering design. The instrument could also be used to track student growth over time, and, with further development, to provide evidence for ABET student outcomes. © American Society for Engineering Education, 2016

VLT/SPHERE robust astrometry of the HR8799 planets at milliarcsecond-level accuracy Orbital architecture analysis with PyAstrOFit

HR8799 is orbited by at least four giant planets, making it a prime target for the recently commissioned Spectro-Polarimetric High-contrast Exoplanet REsearch (VLT/SPHERE). As such, it was observed on five consecutive nights during the SPHERE science verification in December 2014. We aim to take full advantage of the SPHERE capabilities to derive accurate astrometric measurements based on H-band images acquired with the Infra-Red Dual-band Imaging and Spectroscopy (IRDIS) subsystem, and to explore the ultimate astrometric performance of SPHERE in this observing mode. We also aim to present a detailed analysis of the orbital parameters for the four planets. We report the astrometric positions for epoch 2014.93 with an accuracy down to 2.0 mas, mainly limited by the astrometric calibration of IRDIS. For each planet, we derive the posterior probability density functions for the six Keplerian elements and identify sets of highly probable orbits. For planet d, there is clear evidence for nonzero eccentricity ($e \simeq 0.35$), without completely excluding solutions with smaller eccentricities. The three other planets are consistent with circular orbits, although their probability distributions spread beyond $e = 0.2$, and show a peak at $e \simeq 0.1$ for planet e. The four planets have consistent inclinations of about $30\deg$ with respect to the sky plane, but the confidence intervals for the longitude of ascending node are disjoint for planets b and c, and we find tentative evidence for non-coplanarity between planets b and c at the $2 \sigma$ level.Comment: 23 pages, 14 figure

Turkey red prints: Identification of lead chromate, Prussian blue and logwood on Turkey red calico

In this research, printed Turkey red calico from the 19th c. is analysed using conservation-based techniques to identify the materials used in their manufacture. Turkey red production was a significant industry in Scotland, and the textiles found in archives and collections are a valuable part of Scottish heritage and material history. Turkey red prints were produced via a unique dyeing process followed by discharge printing, and the analysis in this paper using SEM-EDX, FTIR, UHPLC, and microscopy confirms they were made as documented in the literature. Here, we show that lead chromate, Prussian blue, and logwood were used to create the distinctive prints. These results are useful to develop material-specific guidelines for storage and display for improved conservation and collection accessibility

Characterisation of oil and aluminium complex on replica and historical 19th c. Turkey red textiles by non-destructive diffuse reflectance FTIR spectroscopy

This work investigates historical and replica Turkey red textiles with diffuse reflectance infrared (DRIFT) spectroscopy to study the coordination complex between cellulose, fatty acids, and the aluminium ions that form the basis of the colour lake. Turkey red was produced in Scotland for around 150 years, and is held in many museum and archive collections. The textile was renowned for its brilliant red hue, and for its fastness to light, washing, rubbing, and bleaching. This was attributed to its unusual preparatory process, the chemistry of which was never fully understood, that involved imbuing cotton with a solution of aqueous fatty acids and then aluminium in the following step. Here we show, for the first time, a characterisation of the Turkey red complex on replica and historical textiles. The development of techniques for non-destructive and in situ analysis of historical textiles is valuable for improving understanding of their chemistry, hopefully contributing to better conservation and display practices. The results show the fatty acids condense onto the cellulose polymer via hydrogen bonding between the Cdouble bond; length as m-dashO and OH of the respective compounds, then the aluminium forms a bridging complex with the fatty acid carboxyl. This contributes to an improved understanding of Turkey red textiles, and shows the useful application of handheld diffuse FTIR instruments for heritage textile research

Optical bistability in a GaAs based polariton diode

We report on a new type of optical nonlinearity in a polariton p-i-n microcavity. Abrupt switching between the strong and weak coupling regime is induced by controlling the electric field within the cavity. As a consequence bistable cycles are observed for low optical powers (2-3 orders of magnitude less than for Kerr induced bistability). Signatures of switching fronts propagating through the whole 300 microns x 300 microns mesa surface are evidenced.Comment: 5 pages 3 figure