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Electrochemistry for Heritage Group

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DataBase / About ElcHer DataBase

ABOUT THE ElcHer VOLTAMMOGRAM DATABASE INITIATIVE

The HelcHer V Voltammogram Database is a dynamic compilation of reference voltammograms of cultural heritage materials contributed by the members of the Group Electrochemistry for Heritage. The database currently contains over 100 voltammograms of minerals, inorganic and organic pigments, mixtures and unclassified materials. In a number of cases the voltammogram is accompanied of IR spectrum, visible spectrum, X-Ray spectrum, light microscopy photograph and electron microscopy photograph.

Voltammograms are formatted with a customized format to incorporate graph. Each file is an independent record.

Voltammograms are publicly viewable, keyword searchable and printable. Digital file downloads of all spectra are available to not-for-profit institutions and individuals.

ElcHer COMMITTEE

Chair

  • Prof. Dr. Antonio Doménech-Carbó, Dpto. Química analítica. Universitat de València, Burjassot, Spain
  • Prof. Dr. María Teresa Doménech-Carbó, Instituto Universitario de Restauración del Patrimonio, Universitat Politècnica de València, Valencia, Spain.

Current members

  • Dr. Laura Osete-Cortina, Instituto Universitario de Restauración del Patrimonio, Universitat Politècnica de València, Valencia, Spain.

INSTRUMENT AND ANALYSIS DETAILS

Voltammetry of microparticles

Electrochemical experiments were performed at 298 K in a three-electrode cell after 10-15 min bubbling of Ar. Square wave voltammograms (SQWVs) and complementary cyclic voltammograms (CVs) were obtained with a CH 660I equipment. Paraffin-impregnated graphite working electrodes were dipped into the electrochemical cell so that only the lower end of the electrode was in contact with the electrolyte solution. This procedure provides an almost constant electrode area and reproducible background currents. A AgCl (3 M NaCl)/Ag reference electrode and a platinum-wire auxiliary electrode completed the conventional three-electrode arrangement. 0.50 M acetic acid plus sodium acetate aqueous buffer (pH 4.75) and 0.10 M HCl were used as electrolytes.

Square wave voltammograms at pigment-modified graphite bars (Alpino, Masats SL, Spain) immersed into 0.25 M HAc/NaAc aqueous solution at pH 4.75. Negative-going scan.  Potential step increment 4 mV; square wave amplitude 25 mV; frequency 5 Hz.

Square wave voltammograms at pigment-modified graphite bars (Alpino) immersed into 0.10 M HCl aqueous solution. Potential step increment 4 mV; square wave amplitude 25 mV; frequency 5 Hz.

 

 FTIR spectroscope

FTIR-1

The IR spectra in the ATR mode of the powdered samples were obtained using a PerkinElmer, model Spectrum BX, program Spectrum Fourier-transform infrared spectrometer with an FR-DTGS (fast recovery deuterated triglycine sulphate) temperature-stabilised coated detector and a MKII Golden Gate Attenuated Total Reflectance (ATR) accessory. A total of 32 scans were collected at a resolution of 4 cm-1 and the spectra were processed using the OPUS/IR software. 

FTIR-2

The IR spectra in the ATR mode of the powdered samples were obtained using a Vertex 70 Fourier-transform infrared spectrometer with an FR-DTGS (fast recovery deuterated triglycine sulphate) temperature-stabilised coated detector and a MKII Golden Gate Attenuated Total Reflectance (ATR) accessory. A total of 32 scans were collected at a resolution of 4 cm-1 and the spectra were processed using the OPUS/IR software.

UV-Vis spectrophotometer

Diffuse reflectance spectra in the UV and visible regions of the samples finely powdered were obtained using a Perkin Elmer Lambda 1,050 recording double-beam spectrophotometer with a special back-scattering configuration. Reflectance measurements were carried out in the range from 200 to 850 cm−1. The device allows a 1 nm wavelength resolution and a precision on the reflectance factor equal to 0.1%.

In order to perform the reflectance measurements, a few micrograms of sample were homogenized with a drop of nujol oil in a small agate mortar. The paste formed was applied as a thin film on a disk of paper Wathman 42 with the help of a scalpel. Thus, a circular surface ( Æ = 5 mm)  was covered of a homogeneous layer of pigment ready for measuring. A second disk in which pure nujol oil was applied was used as blank for subtracting to the samples and thus suppressing the contribution of the nujol used as binder to the reflectance spectrum.

 

Scanning electron microscope-x-ray microanalysis

Chemical composition of the minerals was obtained using a Jeol JSM 6300 scanning electron microscope operating with a Link-Oxford-Isis X-ray microanalysis system. The analytical conditions were: 20 kV accelerating voltage, 2x10-9A beam current and 15 mm as working distance. Samples were carbon coated to eliminate charging effects. Quantitative microanalysis was carried out using the ZAF method for correcting interelemental effects. The counting time was 100 s for major and minor elements. Element percentages were generated by ZAF software on the Oxford-Link-Isis EDX with INCA software.

 

Light microscope

Polarized light microscope Leica DM2500 P (Leica Microsystems. Heidelberg, Germany). Leica Digital FireWire Camera (DFC) with Leica Application Suite (LAS) sotftware has been used for acquiring and processing the digital images.

ABOUT THE SEARCH

Keyword(s) search is a full search of all text fields in the database. Please note that keyword(s) may appear in the filename, common name, supplier, material type or data type field.

The search provides the voltammograms of the selected materials. Complete view of the voltammogram is obtained by clicking on the voltammogram. Details of sample, such as chemical name and working conditions are provided as figure caption. In most materials a list of accompanying spectra and photographs is included at the bottom of the voltammogram. These graphs and images can be also accessed by clicking on the miniaturized figure.

 

HelcHer Data Base General Format

Filename

 Common name of the material followed by two digits in order to distinguish materials of the same chemical composition and different provenance or supplier and followed by the acronym of the data type (vide infra). For example: Ochre yellow 01_SQWV (French), Ochre yellow 02_SQWV (Italian)

Common name

 Common, generic or mineral name of the material are provided in English and Spanish language. For example: Smalt, esmalte, azul esmalte.

Supplier

Provenance or manufacturer of the material. For example: Kremer, Windsor & Newton

Material type

The materials included in the data base are classified in the following types:

Inorganic pigments: natural or synthetic elemental substances, oxides, salts or clayey minerals used as pigments.

Organic pigments: metallic complexes and organic compounds used as pigments or dyes.

Mineral: natural inorganic minerals rarely used as pigments and corrosion products occurring as salts of organic and inorganic acids.

Mixtures: Materials with constituents from multiple classes (such as paint films and composites) and commercial products and formulations. For exam

Data type

Other details of interest such as chemical name, trade names; material sources or working conditions are provided as figure captions.

In the HelcHer database: square wave voltammogram (SQWV), cyclic voltammogram (CV), (IRS) Infrarred absorption spectrum, (UVS) Visible spectrum, (XRS) x-Ray spectrum, (XBEP) backscattered electron photograph,  (XEP) secondary electron

 

List alphabetical of pigments and minerals

Anglesite

Atacamite

Atramentum

Azurite

Bavatian green earth

Brochantite

Burnt green earth

Burnt umber

Carpathian gold ochre

Celadonite green earth

Cerussite

Chrome orange

Chrysokolla 

Cinnabar

Cotunnite

Cuprite

Egyptian blue

Epidote

French ochre

Gold ochre

Green earth

Han blue

Iron glimmer

Iron oxide red

Lead tin yellow

Lead White

Limonite Litharge

Madder

Malachite

Manganese black

Manganese grey

Mars orange

Mars yellow

Massicot

Minium

Naples yellow

Natural sienna

Persian red

Ploss blue

Pyrite

Raw Sienna

Raw umber

Red clay

Red earth

Red ochre

Smalt

Translucent brown-orange

Vagone green earth

Venetian red

Verdigris

Verona green earth

Vesuvianite

Vivianite

White lead

 

 

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Licencia de Creative Commons
ElcHer - 2014 Universitat Politècnica de València, Universitat de València by María Teresa Doménech Carbó, Antonio Doménech Carbó is licensed under a Creative Commons Reconocimiento-NoComercial-SinObraDerivada 4.0 Internacional License.

© 2014 Universitat Politècnica de València - © 2014 Universitat de València

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