The hyphenated thermal analysis-mass spectrometry
technique (TA-MS) was applied for the investigation of the thermal behavior
of reference and aged parchment samples. The kinetic parameters of the process
were calculated independently from all recorded TA and MS signals. The kinetic
analysis showed the distinct dependence of the activation energy on the reaction
progress. Such behavior is characteristic for the multistage mechanism of
The comparison of the kinetic parameters calculated
from the different signals i.e. TG, DSC, MS for H2O,
NO and CO2, however, indicated that they were differently
dependent on the aging of the sample. For the parchment samples, the aging
almost does not change the kinetics of the decomposition calculated from the
DSC data: the influence of aging seems to be too negligible to be detected
by these techniques. On the other hand, the much more sensitive mass spectrometric
technique applied to the kinetic analysis allowed monitoring of visible changes
in the thermal behavior of the parchment samples due to the aging process.
The influence of aging was especially visible when the MS signals of water
and nitric oxide were applied for the determination of the kinetic parameters.
The applied method of the kinetic analysis allowed also the prediction
of the thermal behaviour of reference and aged parchment samples under isothermal
and modulated temperature conditions. Presented results have confirmed the
usefulness of thermoanalytical methods for investigating behaviour of such
complicated systems as leather or parchment.
Summary Thermomagnetometry has been applied to mineralized archaeological iron samples and samples from accelerated corrosion tests. It has successfully quantified the degree of corrosion, measured by the loss of iron, as well as the amount of magnetite formed and water held in the corrosion and adhered soil layers. Thermomagnetometry, thermogravimetric analysis and differential scanning calorimetry have been applied to the reported corrosion products from archaeological iron. Fourier transform infra-red and Raman spectroscopies and X-ray diffraction analyses were undertaken on the residues and at intermediate heating stages, where the thermal analyses indicated, to identify the reaction products.
The degradation of art objects is caused by the combination of all indoor environmental factors. To investigate the deterioration processes in paintings and at the same time to design a risk assessment system, chemical sensors based on artist's materials are developed. Therefore standard paint films of egg yolk tempera with lead white 2PbCO3·Pb(OH)2, azurite 2CuCO3·Cu(OH)2 or smalt were investigated. With accelerated ageing experiments the simulation of natural degradation processes is aimed. First markers for chemical changes were found in the FTIR and TG/DSC measurements.
This article provides a short review of mineral-based pigments used in paintings with examples drawn from technical studies of selected historic paintings. Pigments such as azurite, natural ultramarine, orpiment, and clay earth pigments have been identified. Some examples will also be given of particular case studies which describe the alteration of selected pigments and consequences of these interactions. The second theme shows how use has been made of such interactions in evaluating the effects of environmental impact on paintings and reference is made to previous studies and the application of paint films as dosimeters. Accelerated ageing and site exposure studies are reported, and results provide information on pigment binder interactions. Dynamic mechanical analysis (DMA) and thermogravimetric analysis (TG) have been used to characterise the behaviour of pigments in binding media and to assist in characterising samples from wall paintings. Reference is also made to the occurrence of iron-oxide based minerals present as corrosion products in archaeological iron objects. Examples are given of objects from two archaeological sites in England, the Anglo-Saxon burial site Sutton Hoo in Suffolk, and the burial site in Wetwang, East Yorkshire. It will be shown that post excavation changes occur in the objects and this information is used to inform preventive conservation of these objects, in storage and in display.
Prior to treatment, letters dating from 1665–66 were characterised using SEM, FTIR, ESCA or XPS, TG, TMA and DLTMA. All three
papers were similar in composition and were basically cellulosic materials. Two which had been sent from Lisbon contained
trace amounts of Fe and Cu; these impurities were also present in a letter sent from Dublin. All three letters had been written
with iron gall ink. The letter from Dublin had an additional feature in the ink in the form of small bright specks of mica.
The papers were examined after conservation treatment using the above same techniques in an attempt both to determine and
quantify any changes which had occurred during the treatment process. Scanning electron micrographs showed that propounced
changes had occurred to the surfaces of the treated papers. With XPS it was possible to measure the change in the surface
composition of the papers which occurred on treatment. It was also found that the treatment reduced the thermal stability
of the papers in all three cases.
Thermogravimetric analysis of silica gel has shown that the loss in weight between 30° and 910°C can be quantitatively explained
on the basis of water being lost from three distinct and different populations of sites on the silica gel surface. The results
indicate that the site energies of the three different populations are randomly distributed and, consequently, the resulting
weight loss steps from each population can be described by the integral of a simple normal distribution with temperature.
The calculated weight loss obtained by assuming three different site-groups having randomly distributed adsorption energies
is, within experimental error, coincident with the experimental data. It is also shown that the water evolved from the second
population of sites originates from strongly bound water and may also contain water generated by the condensation of (geminal)
silanol groups contained in the overlapping and neighbouring population.
Authors:G. Hedley, M. Odlyha, A. Burnstock, J. Tillinghast, and C. Husband
Mechanical and surface properties of paint films treated with organic solvents and water have been investigated using a range of thermomechanical and dielectric techniques together with Fourier transform infrared spectroscopy and scanning electron microscopy. Changes in the nature of the surface after treatment were observed. The effect of water, propan-2-ol and propanone (acetone) immersion for 24 hours, and swabbing for a few minutes, on naturally aged 12 years old samples of lead white/linseed oil and burnt sienna/linseed oil could be measured directly in terms of change in the shear modulus of the paint films together with the accompanying change in the ratio of viscous to elastic components present in each system. Generally, the solvent-treated films became harder and showed reduced viscous components, whereas the water-treated samples became softer. There was a change in the dielectric properties of the leached films which pointed to the polar nature of the leachings. FTIR diffuse reflectance spectra supported this conclusion.