Richard Newman

Some Applications of Infrared Spectroscopy in the Examination of Painting Materials

Infrared spectroscopy has been used successfully in the characterization of several types of painting materials. Although most often employed with organic materials, the technique can also yield valuable structural information on many inorganic compounds. Several applications of infrared spectroscopy to inorganic pigments are reviewed, the theoretical bases for the spectra of these materials considered, and characteristic spectra presented. The materials discussed include chrome greens, green earths, and chromium oxide and viridian. Synthetic organic pigments can also be readily identified by infrared spectroscopy and one example (phthalocyanine blue) is discussed. All spectra were obtained from minute samples comparable in size to those often available from art objects, and were recorded using a Fourier transform IR spectrometer.

THE INFLUENCE OF DEACIDIFICATION ON THE DETERIORATION OF PAPER

The influence of calcium carbonate deacidification on the rates of deterioration of commercial rag and newsprint papers at 90°C and 100% R.H. has been examined. Evidence is presented to show that the decreased rate of deterioration resulting from deacidification cannot be accounted for in terms of a decrease in the acid-catalyzed hydrolysis process alone. Atmospheric oxidation, shown to play an important role in the deterioration of the paper samples, is also retarded by deacidification.

MOPA MOPA: SCIENTIFIC ANALYSIS AND HISTORY OF AN UNUSUAL SOUTH AMERICAN RESIN USED BY THE INKA AND ARTISANS IN PASTO, COLOMBIA

Abstract A native South American phenolic resin commonly called mopa mopa was used for many centuries in two cultural contexts, by artisans in the region of Pasto, Colombia (where it is still used), and by the Inka in Peru, where it was used to decorate ceremonial drinking cups known as qeros. It was softened to a rubbery state by heating in water, mixed with colorants, stretched into thin layers and applied as inlay to decorate wooden surfaces of various kinds of objects. The resin comes from trees of the genus Elaeagia, which grows in mountainous regions of western South America from Colombia to Ecuador. Botanical specimens from the two species that are the most likely sources of mopa mopa, Elaeagia pastoensis and Elaeagia utilis, were analyzed along with samples from colonial period objects made in Pasto and samples from Inka qeros. Species-specific identification of the resin is often possible, with E. pastoensis being utilized in Pasto and (probably) E. utilis by the Inka. This conclusion has important implications for the possible connection between the use of mopa mopa in the two widely separated areas.

Characterization of Yellow and Red Natural Organic Colorants on Japanese Woodblock Prints by EEM Fluorescence Spectroscopy

As part of a project designed to systematically identify colorants on Japanese woodblock prints, excitation–emission matrix (EEM), or three-dimensional, fluorescence spectroscopy, equipped with a fiber optic probe, was used to characterize natural yellow and red organic colorants on 18th-century Japanese prints without taking samples. This analysis technique collected emission spectra in the visible region for a sequence of excitation wavelengths at 10 nm steps from 250 to 600 nm. The resultant data set provided characteristic excitation/emission patterns that were used to identify several natural colorants, including safflower, madder, sappanwood, gamboge, flavonoids, berberines, and turmeric. In combination with other non-sampling methodologies, including x-ray fluorescence and fiber optic reflectance spectroscopy, most colorants on the prints were quickly and non-destructively characterized. Based on examination of 213 prints, several patterns of colorant use were observed. The prints often contained more than one yellow, red, or blue colorant. From 1781 to 1801, considered the Golden Age of the Japanese print, it was common to find multiple types of yellows, reds, and blues on a single print. The colorant madder was identified on many of the prints, while gardenia and berberine-containing dyes were found on none. This paper presents the theory, experimental parameters, and limitations of the EEM fluorescence technique. The technique is illustrated using the analysis results of four Japanese woodblock prints.

The occurrence of a titanium dioxide/silica white pigment on wooden Andean qeros: a cultural and chronological marker

A white pigment found on a sub-set of polychromed wooden Andean ritual drinking cups called qeros has been characterized by X-ray diffraction, X-ray fluorescence spectroscopy and Raman spectroscopy as consisting principally of cristobalite (SiO2), anatase (TiO2), and α-quartz (SiO2). This unexpected assemblage of minerals is like that reportedly found in an exposed titanium ore body in southern Peru, an area once part of the Inka Empire. The ore is a close match in color and composition to the white pigment found on the qeros and offers a possible candidate for the geological source of this material. The temporal horizon for the use of this pigment appears to be ca. 1532–1570, correlating with what we refer to here as the Transitional Inka/Early Colonial period, although production of polychromed qeros may have begun before this time and certainly continued well into the eighteenth century or later. Not long after the arrival of the Spanish, this titanium dioxide/silica pigment was replaced by lead white, a result of Spanish influence. We suggest that white pigments on qeros offer material evidence for establishing a chronology for these ritual vessels and that the titanium dioxide/silica pigment on this group of qeros constitutes a previously unidentified, naturally occurring white pigment indigenous to the southern Andes, the first use of which probably dates to the Pre-Columbian period.

Cellulose Nitrate Coatings on Furniture of the Company of Master Craftsmen

Abstract This paper describes the development and use of cellulose nitrate coatings on wood surfaces through a study of clear cellulose nitrate coatings on furniture of the Company of Master Craftsmen, a New York-based company producing furniture between 1926 and 1942. The first patents in this field, as well as published recipes, are compared to results of material analyses. The studys emphasis is on the analysis of cellulose nitrate coatings and changes in their appearance as they age, and types of damage and their causes. Different methods of consolidation, loss compensation, and saturation of the degraded coating were tested. Limits to the known treatment solutions are discussed.

The Methods and Materials of Martin Johnson Heade

Abstract This article presents the results of a study of paintings by the 19th-century American artist Martin Johnson Heade. The project was conducted at the Museum of Fine Arts, Boston, which houses the largest public collection of Heades paintings. Every major period of painting in Heades career is represented here: portraiture, genre, landscape, landscape–still life, and still life. The study included complete photodocumentation and technical examinations of 50 paintings, most from the permanent collection. Paint and ground layers including pigments of 21 paintings of this group were analyzed. Supports, grounds, and paint layers are described in an attempt to follow the progression of the artists style through the years, including the influences of Heades contemporaries. Photomacrography and cross sectional analysis were used to confirm and clarify Heades application of ground and paint layers. Painting methods and materials and a variety of brush strokes and colors are also considered. Particular emphasis is given to pigments, with detailed analytical results presented in tabular form.

Judgment Day for the Turin Shroud

It is a matter of some relief that in the last Newsletter that I gave Professor Harry Goves book Relic, Icon or Hoax? a mainly very warm and positive review, even though it was adverse to the Shrouds authenticity. For one of the great difficulties raised by Dr. Walter McCrones Judgement Day for the Turin Shroud is that if anyone reviews it as a Very Bad Book, then this will simply be lumped in with all the other abuse that its author tells us he has received from Shroudies over the years. A problem being that some of this abuse does not make for good company.