Pigments and Mixtures Identification by Visible Reflectance Spectroscopy

Conceição

et al. 2014

J Raman Spectroscopy

The first archaeological evidence reported for tile production in Portugal was discovered in Santo António da Charneca (SAC), late 15th or early 16th centuries' pottery kiln, south riverside of Tagus River. Samples from this kiln were studied with the use of non‐invasive spectroscopies, namely, μ‐Raman, ground‐state diffuse reflectance absorption, Fourier transform infrared and particle‐induced X‐ray or X‐ray fluorescence emission. These results were compared with the ones obtained for coeval tiles produced in Seville, Spain, originated from Portuguese archaeological sites, because it is well know that the Portuguese King Manuel the First imported in 1498 significant quantities of those tiles to decorate several palaces. The obtained results provided new spectroscopic insights, used to establish similarities but also clear differences regarding the SAC and the coeval Seville tiles found in Portugal. White glaze from both tiles gave evidence about the use of tin oxide as whitening agent and lead oxide as glassy agent. Cobalt oxides were also used as blue pigments in the two production centres. The brown and amber pigments in the samples from SAC derive from the manganese oxides dispersed in the lead–tin glaze, and kentrolite crystals were identified by μ‐Raman in these tiles. In the arista and cuerda‐seca tiles from Seville, diopside was detected. Divalent copper also exists in the green glaze matrix but in small amounts, which did not allow the Raman detection of the copper compound's microcrystals. However, diffuse reflectance measurements point to malachite green as responsible of green coloration. The Seville pastes contain calcium carbonate, although the SAC pastes do not evidence significant amounts of that compound in its composition. All the SAC pastes evidenced a high silica level, and quartz and anatase were clearly detected in the paste and possibly kaolinite. The Raman signals of orthoclase and calcium carbonate were detected in the Seville tiles. Copyright © 2014 John Wiley & Sons, Ltd.

Section: Resultsmentioning

confidence: 99%

Portuguese 16th century tiles from Santo António da Charneca's kiln: a spectroscopic characterization of pigments, glazes and pastes

Conceição

et al. 2014

J Raman Spectroscopy

“…It is interesting to note that the HSI equipment used in this study has a spectral resolution of 0.67 nm which is more than sufficient [54,55] to discern such peaks and troughs as may be present in the reflectance spectra involved and may even lead to data redundancy [55]. This would slow down any computational work done on the reflectance spectra (as the computer would carry out calculations on all the data regardless of its redundancy).…”

Section: Hyperspectral Imagingmentioning

confidence: 99%

Comparing the effectiveness of hyperspectral imaging and Raman spectroscopy: a case study on Armenian manuscripts

et al. 2018

There is great practical and scholarly interest in the identification of pigments in works of art. This paper compares the effectiveness of the widely used Raman Spectroscopy (RS), with hyperspectral imaging (HSI), a reflectance imaging technique, to evaluate the reliability of HSI for the identification of pigments in historic works of art and to ascertain if there are any benefits from using HSI or a combination of both. We undertook a case study based on six Armenian illuminated manuscripts (eleventh-eighteenth centuries CE) in the Bodleian Library, University of Oxford. RS, and HSI (380-1000 nm) were both used to analyse the same 10 folios, with the data then used to test the accuracy and efficiency of HSI against the known results from RS using reflectance spectra reference databases compiled by us for the project. HSI over the wavelength range 380-1000 nm agreed with RS at best 93% of the time, and performance was enhanced using the SFF algorithm and by using a database with many similarities to the articles under analysis. HSI is significantly quicker at scanning large areas, and can be used alongside RS to identify and map large areas of pigment more efficiently than RS alone. HSI therefore has potential for improving the speed of pigment identification across manuscript folios and artwork but must be used in conjunction with a technique such as RS.

Color Research & Application

Section: Introductionmentioning

confidence: 99%

“…A literature survey revealed that fiber optic reflectance spectroscopy is also studied for pigment quality analysis and a method for measuring undertone (tint tone) is based on the ratio of absorbance measurements of a dilute slurry of TiO 2 at 400 and 700 nm. [8][9][10][11][12] Tunstall 13 discloses a method in his patent for measuring the mean particle size and/or SD of particles that involves illuminating a suspension of the particles with three beams of radiation of wavelengths R 1 , R 2 , and R 3 , and measuring the beam intensities passing through the suspension. The results are compared with those of the liquid medium free of particles and attenuation ratios (reduction in the intensity of radiation beam) of the beams at wave lengths R 1 and R 3 and at R 2 and R 3 are compared with previously calculated values for these ratios 13 .…”

Section: Introductionmentioning

confidence: 99%

A spectroscopic method for quick evaluation of tint strength and tint tone of titania (rutile) pigment and factors affecting them

Sharafudeen

2018

Titanium dioxide (TiO2) manufacturing industries measure optical properties such as brightness, colour, tint strength, tint tone, gloss, scatter coefficient, and others to ensure the quality of the product. Product characterization and process control generally focus on the optical properties, which determine its quality. In this work, titania rutile pigment with varying tint strength and tint tone is analyzed and a correlation is established between particle size and the optical properties such as tint strength and tint tone. It is observed that optical properties of titania pigment depends on the particle size as well as particle size distribution. A relatively faster evaluation of tint strength and tint tone can be made using the reflectance and particle size measurements. Analytical samples were prepared by ultrasonic dispersion of pigment in water containing calgon as dispersing agent. To verify the accuracy of the method, pigment tint strength and tint tone obtained from this study are compared with those resulting from traditional analysis. The results showed that the new method is viable.