Colourimetric Measurements Research Articles

Superhydrophobicity, Photocatalytic Self-Cleaning and Biocidal Activity Combined in a Siloxane-ZnO Composite for the Protection of Limestone.

The erosion phenomena of the natural stone in cultural heritage are induced by various sources. Consequently, the development of multifunctional protective materials that combine two or more useful properties is an effective strategy in addressing the synergistic effects of various erosion mechanisms. A multifunctional coating, consisting of a silane-based precursor and zinc oxide (ZnO) nanoparticles (NPs), is produced and tested for the protection of limestone. The hybrid coating combines the following three properties: superhydrophobicity, including water-repellency, photocatalytic self-cleaning and biocidal activity. The relative concentration of the NPs (0.8% w/w), used for the suggested composite coating, is carefully selected according to wetting studies, colourimetric measurements and durability (tape peeling) tests. The non-wetting state is evidenced on the surface of the composite coating by the large contact angle of water drops (≈153°) and the small contact angle hysteresis (≈5°), which gives rise to a physical self-cleaning scenario (lotus effect). The photocatalytic chemical self-cleaning is shown with the removal of methylene blue, induced by UV-A radiation. Moreover, it is shown that the suggested coating hinders the incubation of E. coli and S. aureus, as the inhibitions are 94.8 and 99.9%, respectively. Finally, preliminary studies reveal the chemical stability of the suggested coating.

Preliminary Study of Stone Sawing Sludges-based Alkali Activated Materials (AAMs) for the Conservation of Archaeological Ceramics

This paper presents research into the feasibility of using stone sawing sludge-based Alkali Activated Materials (AAMs) for conservation of Cultural Heritage. Sawing sludges are a stone processing waste product resulting from the mixing of rock powder with the water used to cool down the cutting blades. The chemical composition of the sawing sludges, when aluminosilicatic, is suitable for acting as a precursor to produce AAMs. AAMs are known for their low environmental impact and versatility since their existence is drawn from recycling waste materials. One of their possible applications is in the conservation of Cultural Heritage objects. This work presents a preliminary investigation into three sawing sludge-based AAMs with different mineralogical compositions and contributes to formulating guidelines for applying them as fillers on modern and archaeological ceramic pottery based on the evaluation of their workability, appearance and physical properties over time from the moment of application and up to 30 days. Dynamic Vapor Sorption and X-Ray Diffraction results provided an overview of the structural and mineralogical changes under high RH conditions, where the tested AAMs showed a type II isotherm curve, as expected for concrete-like materials, as well as disappearance of thermonatrite after one isothermal cycle. Ultrasonic Pulse Velocity test demonstrated the general homogeneity of the AAMs despite the lower velocity exhibited by one of the formulations, probably due to its internal pore distribution and possible presence of microstratification. The Oddy tests, application tests and colourimetric measurements evidenced the advantages and weaknesses of the AAMs, with overall encouraging results ensuing investment in further in-depth studies of these innovative conservation materials in view of their future use in the field of conservation of Cultural Heritage as a result of a circular economy model.

PH-Responsive textile with anthocyanin-laden hydrogel yarns: a colorimetric and feasibility study

Abstract Responsive materials can transform their visual appearance in reaction to environmental stimuli. One example of such responsiveness involves the use of plant-based anthocyanins as pH-mediated allochroic pigments. Despite the increasing interest and applications of this pigment, its applications in urban contexts are very limited. By using pH-mediated colour change as a phenomenon to trial a colourimetric quantitative framework, this study seeks to bridge smart material design with colour science approaches to enable future scale-up applications. The colour values of anthocyanins immobilised in sodium alginate-based hydrogel discs and yarns were measured in response to varying pH values. The colourimetric measurements in CIELAB colour space provided a device for setting independent colour values that demonstrated a clear pattern across the pH range of 1–12. The colour difference (ΔE00) of mean colour values was perceivably different across the pH scale, with a minimum value of 2.7. Key variables of the process have been summarised, and their relationships have been discussed. Finally, a proof-of-concept small-scale textile prototype encompassing anthocyanin-laden hydrogel yarns was developed. The findings of this study contribute towards the integration of non-destructive means of colour measurement as a quantitative tool for biochemical process evaluation.

Characterization of fortified compound milk chocolate with microcapsulated chia seed oil

Fortified compound milk chocolates were prepared by adding different percentages (5%, 10%, and 15% w/w) of microcapsules containing chia seed oil (CSO). Sensory evaluation showed that the presence of the microcapsules did not have a significant effect (P > 0.05) on taste, texture and overall acceptance compared to the control. After storage for 120 days, sensory evaluations showed lower scores, which were not significant. Physicochemical properties of the fortified chocolates containing 10% of microcapsule were investigated at fresh and stored (120 days). Water activity and moisture of the chocolates were obtained in the range of 0.25–0.40 and 0.9–0.7%, respectively. According to the texture analysis hardness of fortified chocolate was less than control, however, it not significant. Thermal analysis showed that melting behavior of the fortified chocolate was affected by the wall material of microcapsules but not with CSO. Surface topographic and colourimetric measurements revealed the significant blooming of stored chocolate compare to control. The results indicated that the fortified chocolates can preserve their characteristics in comparison with the control chocolate.

Esthetic performance of thermochromic pigments in cataphoretic and sprayed coatings for outdoor applications

AbstractThis study aims to assess the aesthetical performances of thermochromic coatings for outdoor applications. In details, this work focuses on the efficiency of thermochromic pigments inside cataphoretic and sprayed primers, evaluating the possible synergic effect of a protective transparent topcoat. The structure of thermochromic pigments is examined by optical microscope, and their color‐changing behavior is evaluated by colourimetric measurements. Colourimetric analyses are also carried out to monitor the thermochromic performances of the coatings during exposure to an aggressive NaCl solution and UV‐B radiations, and to assess the protective role of the top‐coat. In addition to that, wet‐ and dry‐abrasion tests are carried out to define the suitability of these coatings for outdoor applications where good resistance to mechanical damage is required. Thus, this work evidences the better aesthetical features of the cataphoretic primer, which, however, particularly suffers from chemical–physical degradation processes. Nevertheless, the application of the transparent topcoat allows to maintain the integrity of the cataphoretic primer. The double‐layer coating exhibits a remarkable color‐changing behavior even when subjected to degradation phenomena due to exposure to aggressive environments.

Accelerated Ageing Procedures to Assess the Stability of an Unconventional Acrylic-Wax Polymeric Emulsion for Contemporary Art.

This research evaluates the stability of an aqueous emulsion of acrylic copolymers and waxes. Edelwachs, generally applied on wood, has been recently used as an unconventional medium in contemporary painting. Through Pyrolysis–Gas Chromatography–Mass Spectrometry (Py-GC-MS) and Fourier Transformed Infrared Attenuated Total Reflectance (FT-IR-ATR) analyses, the composition of Edelwachs was defined as a mixture of acrylic polymers (MA, MMA, nBA, nBMA), Carnauba and microcrystalline waxes and additives. Mock-ups-obtained mixing Edelwachs with titanium white, zinc white and ultramarine blue were subjected to UV, high temperatures, and high relative humidity accelerated ageing. The effect of the ageing procedures was evaluated through optical microscopy, colourimetric measurements, FT-IR-ATR, Thermogravimetry and Differential Scanning Calorimetry (TG-DSC) and wettability measures. FT-IR-ATR spectra do not show significant variations in terms of chemical stability, indicating a fair stability of Edelwachs as a painting binder. UV and high temperature treatments show the most relevant effects in terms of colorimetric changes (increasing of b*) and thermal stability. The TG-DSC highlights the influence of the pigments (specifically zinc white) mainly on the thermal behaviour of the acrylates. The unexpected decrease of wettability of the paint films, registered after ageing, may indicate a possible phase separation among acrylates and waxes.

Hydrophobic Zinc Oxide Nanocomposites for Consolidation and Protection of Quartzite Sculptures: A Case Study

Quartzite sculptures are considered some of the most impressive and informative archaeological remains which have been found in the most of Egyptian archaeological sites. Regrettably, quartzite sculptures suffer from many deterioration aspects such as granular disintegration, scaling, cracking, efflorescence, soiling, microbiological colonization. Water is the main aggressive deterioration factor of stones and stone-based monuments, as in addition to its direct role in deterioration mechanisms, it plays as a catalyst in the physicochemical and microbiological deterioration processes.During the last two decades, polymer nanocomposites have widely been applied in the field of cultural heritage conservation due to their unique physical and chemical characteristics. Zinc oxide nanoparticles are among the most important semiconductive nanomaterials that have been applied in the fabrication of nanocomposites. They have been demonstrated to improve the physicochemical and mechanical properties of polymers. In addition, zinc oxide nanoparticles were mixed with polymers in order to fabricate superhydrophobic and self-cleaning protective materials.The aim of this paper is to evaluate the efficiency of zinc oxide nanocomposites, in order to select the best of them for the consolidation and protection of a colossal quartzite statue of Ramesses II. The properties of the treated quartzite samples were comparatively examined by colourimetric measurements, static water contact angle, compressive strength, and scanning electron microscope.

Nanomaterials for Combined Stabilisation and Deacidification of Cellulosic Materials-The Case of Iron-Tannate Dyed Cotton.

The conservation of textiles is a challenge due to the often fast degradation that results from the acidity combined with a complex structure that requires remediation actions to be conducted at several length scales. Nanomaterials have lately been used for various purposes in the conservation of cultural heritage. The advantage with these materials is their high efficiency combined with a great control. Here, we provide an overview of the latest developments in terms of nanomaterials-based alternatives, namely inorganic nanoparticles and nanocellulose, to conventional methods for the strengthening and deacidification of cellulose-based materials. Then, using the case of iron-tannate dyed cotton, we show that conservation can only be addressed if the mechanical strengthening is preceded by a deacidification step. We used CaCO3 nanoparticles to neutralize the acidity, while the stabilisation was addressed by a combination of nanocellulose, and silica nanoparticles, to truly tackle the complexity of the hierarchical nature of cotton textiles. Silica nanoparticles enabled strengthening at the fibre scale by covering the fibre surface, while the nanocellulose acted at bigger length scales. The evaluation of the applied treatments, before and after an accelerated ageing, was assessed by tensile testing, the fibre structure by SEM and the apparent colour changes by colourimetric measurements.

Crypsis Decreases with Elevation in a Lizard

Predation usually selects for visual crypsis, the colour matching between an animal and its background. Geographic co-variation between animal and background colourations is well known, but how crypsis varies along elevational gradients remains unknown. We predict that dorsal colouration in the lizard Psammodromus algirus should covary with the colour of bare soil—where this lizard is mainly found—along a 2200 m elevational gradient in Sierra Nevada (SE Spain). Moreover, we predict that crypsis should decrease with elevation for two reasons: (1) Predation pressure typically decreases with elevation, and (2) at high elevation, dorsal colouration is under conflicting selection for both crypsis and thermoregulation. By means of standardised photographies of the substratum and colourimetric measurements of lizard dorsal skin, we tested the colour matching between lizard dorsum and background. We found that, along the gradient, lizard dorsal colouration covaried with the colouration of bare soil, but not with other background elements where the lizard is rarely detected. Moreover, supporting our prediction, the degree of crypsis against bare soil decreased with elevation. Hence, our findings suggest local adaptation for crypsis in this lizard along an elevational gradient, but this local adaptation would be hindered at high elevations.

A novel method for the analysis of particle coating behaviour via contact spreading in a tumbling drum: Effect of coating liquid viscosity

Spray coating is a common method of distributing liquids over powders, especially in the pharmaceutical, detergent and food industries. During this process, liquid drops are deposited on the surface of particles. Liquid is then transferred between particles via particle collisions, in a process called liquid contact spreading. This contact spreading process facilitates inter-particle coating, in which wetting, de-wetting, mixing and drying are occurring simultaneously. This work presents the first experimental study of the mechanism of liquid contact spreading. In this work, a novel experimental method has been developed to investigate the mechanism of contact spreading, incorporating a newly developed image analysis technique, based on colourimetric measurements, to quantitatively determine coating behaviour via contact spreading.Here, experiments designed to isolate the contact spreading coating mechanism were performed in a tumbling drum using a model material system; alumina particles and dyed polyethylene glycol solutions of varying viscosities. The coating uniformity was quantified by the variation in inter-particle coating; the coefficient of variation (CoV). For all systems, the uniformity of the coating increased with time until the CoV decreased to an asymptotic value. The rate of the decrease in the CoV was successfully fitted using an exponential decay function.The viscosity of the coating solution had a significant effect on the rate of liquid transfer; the lower the viscosity the faster the contact spreading process. This effect is attributed to differences in the formation and stability of liquid bridges between the particles, influencing the extent of liquid transfer. The results also show that in most cases examined here, viscous forces play a main role in the contact spreading process, and the contribution of capillary forces are minimal. This understanding could assist with the design and scale up of wet coating processes.

Reflectance colourimetry as a method for estimating the approximate quantity of non-carbonate components in limestones: A case study in the Mokrá Quarry (Czech Republic)

This paper demonstrates the applicability and usefulness of colourimetry as a fast and simple tool to assess the quality of limestones for cement and lime industry raw materials, a field where colourimetric measurements have not yet been applied. The results of the colourimetric analysis in a large sample set from the Mokrá Quarry in the Moravian Karst (NE from Brno, Czech Republic) and comparisons with the results obtained by other methods are presented here. The studied samples belong to two lithologically different series of strata: the Macocha Formation and the Líšeň Formation. Limestones of these formations differ in structure, the contents of their non-carbonate components and, therefore, in colour as well. The samples were prepared in four ways for the purposes of colourimetric measurements: i) unpolished bulk samples (fracture planes were measured), ii) polished sections, iii) powder in a plastic bag, and iv) uncovered powder. Each of these four ways led to different results, which were expressed using the CIE L*a*b* colour space. The L* (specific lightness) value gives an approximate estimate as to the amount of non-carbonate components. The specific lightness value can be used for assigning a sample to a lithostratigraphic member and, in many cases, possibly also to a correlation among members.

Lighting Design for Energy Sustainability, Information, and Perception. A Museum Environment as a Case Study

The aim of our research is to investigate the physical connection between light, perception, and information by means of an integrated methodological approach. The proposed method was used for sustainable lighting design aiming at light efficacy and quality, visual perception, communication, and energy saving. Three types of synergic measurement were carried out: photometric, colourimetric, and perception measurements. Starting from the results and the post-processing of photometric and colourimetric measurements on different light sources and fresco surfaces, by applying the eye-tracking technique for eye movement analysis of a people sample, entropy calculations were carried out. The results of observer perception and preferences, patterns of their visual scanning due to different LED (Light Emitting Diode) sources, were quantified by means of Shannon entropy calculation and, consequently, the information content of images that each light source can transmit. A new lighting proposal, based on the use of LED sources characterized by a spectral emission of light in strong compliance with surface colour and relevant transmission image content information was suggested and checked by transient simulations. Our proposal was based on sustainability because this concept is linked to developing perception and visual wellbeing, information, light communication, and lower energy consumption for maintenance, but especially for preventive conservation and the protection of works of art by means quality of light.

Classification and compositional characterization of different varieties of cocoa beans by near infrared spectroscopy and multivariate statistical analyses

Effective and fast methods are important for distinguishing cocoa varieties in the field and in the processing industry. This work proposes the application of NIR spectroscopy as a potential analytical method to classify different varieties and predict the chemical composition of cocoa. Chemical composition and colour features were determined by traditional methods and then related with the spectral information by partial least-squares regression. Several mathematical pre-processing methods including first and second derivatives, standard normal variate and multiplicative scatter correction were applied to study the influence of spectral variations. The results of chemical composition analysis and colourimetric measurements show significant differences between varieties. NIR spectra of samples exhibited characteristic profiles for each variety and principal component analysis showed different varieties in according to spectral features.

Heat-induced alteration of glauconitic minerals in the Middle Stone Age levels of Blombos Cave, South Africa: Implications for evaluating site structure and burning events

In this paper we conduct geochemical and colourimetric measurements of glauconite grains in micromorphological thin sections from the Middle Stone Age site of Blombos Cave, South Africa, to investigate the formation, internal structure and reworking of heat-exposed cave deposits that are related to prehistoric burning events. Controlled heating experiments were first carried out on glauconite-rich loose sediments and block samples, both of which were collected from the Blombos Cave bedrock. The control samples were then subjected to Fourier transform infrared spectrometry (FTIR), microscopic Fourier transform infrared spectrometry (micro-FTIR) and petrographic-colourimetric analyses. The control experiment shows that glauconitic minerals undergo a gradual and systematic colour change when temperatures reach higher than c. 300–400 °C, primarily due to dehydration and iron oxidation. They also undergo clear structural changes when temperatures reach higher than c. 550 °C due to dehydroxylation and mineral transformation. By assessing the nature and degree of heat-induced optical and molecular alteration in glauconitic minerals, we demonstrate how glauconite grains in thin sections can be classified by the temperature to which they were exposed (20–400 °C, >400 °C, >600 °C and >800 °C). To assess the archaeological relevance of our controlled heating experiment, we applied this glauconite classification scheme to >200 grains found in three micromorphological thin sections of a Middle Stone Age (MSA) combustion feature. These grains were individually geo-referenced within the local coordinate system of Blombos Cave, through a thin-section-based GIS mapping procedure. With improved spatial control, we were able to study both the general distribution of non-altered and heat-altered glauconite grains in their original sedimentary context, as well as to calculate heat distribution models that cover the entire sampled section. This combined geo-chemical, optical and spatio-contextual approach provides insights into more elusive aspects of MSA site structure and burning events, such as heat intensity, burning frequency, temperature distribution, internal hearth structure and post-depositional reworking. The workflow we propose may easily be implemented and adapted to other archaeological contexts and to analogous sedimentary materials that show comparable heat-induced alteration patterns.

Facile Method to Prepare Superhydrophobic and Water Repellent Cellulosic Paper

Silica nanoparticles (7 nm) were dispersed in solutions of a silane/siloxane mixture. The dispersions were applied, by brush, on four types of paper: (i) modern, unprinted (blank) paper, (ii) modern paper where a text was printed using a common laser jet printer, (iii) a handmade paper sheet detached from an old book, and (iv) Japanese tissue paper. It is shown that superhydrophobicity and water repellency were achieved on the surface of the deposited films, when high particle concentrations were used (≥1% w/v), corresponding to high static (θS ≈ 162°) and low tilt (θt < 3°) contact angles. To interpret these results, scanning electron microscopy (SEM) was employed to observe the surface morphologies of the siloxane‐nanoparticle films. Static contact angles, measured on surfaces that were prepared from dilute dispersions (particle concentration <1% w/v), increased with particle concentration and attained a maximum value (162°) which corresponds to superhydrophobicity. Increasing further the particle concentration did not have any effect on θS. Colourimetric measurements showed that the superhydrophobic films had negligible effects on the aesthetic appearance of the treated papers. Furthermore, it is shown that the superhydrophobic character of the siloxane‐nanoparticle films was stable over a wide range of pH.

Honey characterization using computer vision system and artificial neural networks

This paper reports the development of a computer vision system (CVS) for non-destructive characterization of honey based on colour and its correlated chemical attributes including ash content (AC), antioxidant activity (AA), and total phenolic content (TPC). Artificial neural network (ANN) models were applied to transform RGB values of images to CIE L∗a∗b∗ colourimetric measurements and to predict AC, TPC and AA from colour features of images. The developed ANN models were able to convert RGB values to CIE L∗a∗b∗ colourimetric parameters with low generalization error of 1.01±0.99. In addition, the developed models for prediction of AC, TPC and AA showed high performance based on colour parameters of honey images, as the R2 values for prediction were 0.99, 0.98, and 0.87, for AC, AA and TPC, respectively. The experimental results show the effectiveness and possibility of applying CVS for non-destructive honey characterization by the industry.

Study of archaeological underwater finds: deterioration and conservation

This study is aimed at an assessment of the methodologies, instruments and new applications for underwater archaeology. Research focused on study of the various kinds of degradation affecting underwater finds and stone materials aged in underwater environment, efficiency evaluation of various surface cleaning methods and study and mixing of protective products with consolidating resins and antimicrobial biocides to be applied to restored underwater finds. Transmitted light optical microscopy and scanning electron microscopy (SEM) were used to study surface biofilms and the interactions with samples of different stone materials such as brick, marble and granite immersed in the submarine archaeological area of Crotone (South of Italy). Surface cleaning tests were performed with application of ion exchange resins, EDTA, hydrogen peroxide and ultrasound techniques. Capillary water absorption, simulated solar ageing and colourimetric measurements were carried out to evaluate hydrophobic and consolidant properties; to assess biocidal efficacy, heterotrophic micro-organisms (Aspergillus niger) were inoculated on agar plates and growth inhibition was measured.

A new diquat derivative appropriate for colourimetric measurements of biological materials in the presence of paraquat.

A new colourimetric method is described for the quantification of diquat using a yellow-coloured derivative produced by heating diquat in alkaline solution at 80 degrees C. The absorption maximum of the yellow derivative is 420 nm and the molar absorption coefficient is 2.76 x 10(4) (0.15 in 1 microgram diquat/ml with 1 cm light path). The absorption at 420 nm shows a linear concentration dependence in the range 0.1-10 micrograms/ml and fading of the colour is about 5% after 1 h. Under the same conditions, paraquat does not produce any coloured products. The concentration of diquat in the solution containing both diquat and paraquat can be determined by the absorption of diquat derivative at 420 nm without interference from paraquat. By adding sodium dithionite to the solution the concentration of paraquat can be determined by the absorption of paraquat radicals at 600 nm without interference from diquat, because the yellow derivative does not react with dithionite. This yellow diquat derivative can be extracted completely with cyclohexanol by saturating the solution with Na2SO4. The absorption maximum in cyclohexanol shifts to 440 nm with the same molar absorbance and the same half-band width as in water. Fading of the colour is less than 5% after 24 h in cyclohexanol. Perchloric acid (3%) and trichloroacetic acid (4.5%) which are often used for deproteinization of tissue homogenates, do not inhibit production of the coloured derivative at pH 13.5 or extraction of the derivative with cyclohexanol. This method is suitable for a quick determination of small amounts of diquat in tissues, since the extraction with cyclohexanol not only concentrates the derivative rapidly but also quite efficiently eliminates the coloured substances in tissue homogenates. The detection limit of diquat is 0.02 microgram/ml for blood and 0.05 microgram/g for liver when 1 ml or 1 g is used for analysis. In three human cases of fatal intoxication, both paraquat and diquat were quantified using 50 microliters of serum. In non-toxic dosing of diquat to rats for 14 days, the diquat level was highest in the spleen followed by the kidneys.

A new diquat derivative appropriate for colourimetric measurements of biological materials in the presence of paraquat

A new diquat derivative appropriate for colourimetric measurements of biological materials in the presence of paraquat

Muscle pigmentation changes during and after spawning in male and female rainbow trout,Oncorhynchus mykiss, fed dietary carotenoids

The dynamics of astaxanthin and canthaxanthin were studied through an 11-month feeding experiment by following carotenoid deposition in male and female rainbow trout muscle, during and after spawning. Carotenoids were analysed by chromatography (HPLC), muscle colour was measured by a colourimeter and visual rank evaluation. In both sexes, a decrease in the muscle carotenoid content was observed at spawning time. The recovery of the muscle pigmentation differed between females and males, but seemed not to be influenced by the type of carotenoid additives in feed. The carotenoid content of the female muscle increased rapidly after spawing, while in the male this increase was slower. Eighteen weeks after spawing, carotenoid concentrations in the muscle of females corresponded to those before spawning, while in males they reached only one third of that amount. Significant correlations were found between chemical analysis, colourimetric measurements and visual rank evaluation.