μS/cm: micro siemens per centimeter (conductivity measurement unity), SI unit is
siemens per meter
Nm: nanometer ( 1 nm = 1×10−9 m = 1×10−3 μm)
pH: measurement scale of the acidity or basicity of solutions.
Ppb: parts per billion (1 part in 1,000,000,000 or one microgram per liter)
Ppm: parts per million (1 part in 1,000,000 or one milligram per liter)
RH: Relative Humidity
Agar (agarose): a gelatinous substance, obtained from algae, used as an agent to
Algorithm: a process or set of rules to be followed in order to solve a mathematical
problem or to complete a computational process.
Amorphous: or non-crystalline is a solid that, on a molecular scale, lacks the
long-range order that characterizes crystalline solids. Amorphous materials include glass, gels, some
polymers, thin films, etc.
Anaerobic microorganism: a microorganism that does not require oxygen for growth.
Analyte: the substance or chemical component of interest in an analytical
Analytical methods: Methods used for the isolation, identification, detection, and
quantification of chemical substances.
Beta particle: subatomic particles, equivalent to electrons, ejected from certain
Biocide: a substance that kills microorganisms or inhibits their multiplication.
Biological analysis: Study of the nature and growth of micro- and macro-organisms
Bioreceptivity: the potentiality of a material to be colonized by microorganisms.
Birefringence: the optical property of materials that have different refractive
on the orientation of the crystalline lattice with respect to the incident light. These materials
Black crust: are grey-black accumulation areas of environmental deposition
damage historical buildings and are usually a result of atmospheric pollution. Black crusts contain:
gypsum, carbonaceous particles deriving from fuel combustion, fungi etc.
Cambium: layer of cells between the wood and the bark
Chemical mapping: consists in creating a visual image of components distribution by
a large number of spectra in a determined space and time.
Compound analysis: Process where a sample of some material is analyzed for its
compounds. Can be qualitative and/or quantitative.
Compound (chemical): A substance formed from two or more elements chemically united in
Coulombic: refers to Coulomb’s law, the law of physics describing the electrostatic
that occurs between electrically charged particles.
Cross section: a mm-sized sample cut out of the investigated specimen, embedded in
a resin and
polished with different grain-sized sandpapers until its surface is flat for stratigraphic
with an optical microscope. Cross sections are prepared for observing layered samples.
Crystal: a solid consisting of a symmetrical, ordered, three-dimensional
aggregation of atoms,
ions or molecules.
Crystalline structure: refers to the unique arrangement of elements* or molecules
in a crystalline
Declination: angle between the geographic north (also called « true » north) and
north of the EMT; angle between the geographic north and sample’s TRM.
De-excitation: the transition an excited system (atom, molecule or nucleus)
undergoes in order
to return to a lower energy level or to drop back to the ground state.
Dehydroxylation: is a chemical process that eliminates a hydroxyl group, -OH, from
Destructive analysis: after sampling, the sample is analyzed and destroyed
the process. Once the analysis is finished the sample cannot be used for another technique.
Detection limit: lower limit of detection, or LOD (limit of detection) is the
lowest quantity of a
substance that can be distinguished from the absence of that substance by the equipment.
Diffraction: Diffraction occurs because the wavelengths of the incident X-rays
are similar to the
spacings between the planes of the crystal. Diffraction is a constructive interference of waves (in
this case X-rays) that takes place when X-rays are scattered by atoms.
Diffraction grating: is an optical component used in monochromators or
spectrometers. It splits and diffracts light beams into different directions.
Dose: a radiation dose is the amount of energy transfer due to the ionising
absorbed dose is the quantity of energy deposition caused by the radiation to the material
Dosimeter: device (or material) which records the radioactivity.
Efflorescence: a white, crystalline or powdery deposit of water-soluble salts on
the surface of stone and other building materials due to evaporation of H2O, which migrate from the
masonry towards the surface, causing structural and aesthetic deterioration.
Element: Each of more than one hundred primary constituents of matter that cannot
be chemically interconverted or broken down into simpler substances. Each element is distinguished by
its atomic number, i.e. the number of protons in the nuclei of its atoms (see periodic table).
Elemental analysis: Process where a sample of some material is analyzed for the
chemical elements it is composed of. Can be qualitative and/or quantitative.
Eluent: The eluent is the solvent used to separate and carry the analytes
throughout the chromatographic column. In HPLC and Ion* Chromatography it is the liquid mobile phase,
whereas in Gas Chromatography it is the carrier gas. Endolithic (micro)organisms: an endolithic
(micro)organism lives inside rock cavities or in
the pores between mineral grains of rocks. Such organisms can be: bacteria, lichens, fungi,
Gilding: is the decorative method of golden-leaf coating of a material’s surface.
Grog: Grog is clay that has been finely ground after firing. It is used as
additive in ceramic
Heartwood: also duramen: older, non-living central wood of a tree
Hydraulicity index: SiO2 + Al2O3 + Fe2O3 / CaO + MgO ratio, shows the ability of a
binder to set
Hygroscopic: is called a material that attracts and retains moisture from its
Inert: does not interact chemically with the sample.
Ion: an atom or molecule with a net electric charge due to the loss or gain of one or
Ion analysis: Process that separates and quantifies ions and polar molecules.
Ionization: the process by which an electrically neutral atom or molecule acquires a
negative or positive charge by gaining or losing electrons, respectively, to form ions*.
Inclination: angle between the earth magnetic field and the local horizontal plan;
angle between the sample magnetization and the horizontal plan where it was fired.
Invasive analysis: sample from the original material is needed, so it is destructive
towards the building.
Isotropy/anisotropy: are optical properties of materials. An isotropic crystal does
not exhibit birefringence, whereas in anisotropic ones the refractive index varies with the orientation
light propagation through the crystal lattice.
KBr pellet: ionic compound* that usually does not have any peaks in the IR range,
so it does not interfere with the sample’s peaks on the spectrum. Mass-to-charge ratio: ions*
have different masses and charges and when they are subjected
to electromagnetic fields, they behave, i.e. are deflected by the electromagnetic field, differently.
Due to this physical phenomenon very fine analysis is possible.
Mesh: basic element of a grid such as the opening size of a sieve.
Micromorphology: Study at a microscopic level of the form and structure of materials or
organisms through microscopy.
Monochromator: is an optical device that separates and transmits a narrow band of
Mordant: is a mixture – usually of a siccative oil or a natural resin or both – used to
fix a metal coating on another material.
Nebulizer: a device that converts a liquid sample into an aerosol, because only
droplets of a few mm in diameter can be injected into the plasma.
Nital: a solution of alcohol and nitric acid commonly used for etching of metals.
Non-destructive analysis: after sampling, the analysis does not destroy the
sample, it remains intact and may be used for another technique.
Non-invasive analysis: direct analysis on the material in situ, without affecting it.
Nuclear: related to the atomic nucleus. In this article the term “nuclear process"
refers to any type of radioactive decay by which the nucleus of a radioactive (unstable) atom loses
energy by emitting ionizing radiation (alpha particles, beta particles, and gamma rays).
Palafitte: pile dwelling or stilt house raised on piles over the soil or a body of
Paraloid B72: an acrylic resin (organic polymer) widely used in conservation.
Particle accelerator: A particle accelerator is a device that uses electromagnetic fields
to speed up and increase the energy of a beam of particles and magnetic fields to steer and focus them
Patina: a composite layer of corrosion products, deposit materials and non-oxidized
substances on a material’s surface containing also – partially - information of the original surface
Penetrometer: a device used to test the strength of a material.
Petri dish: a shallow cylindrical plastic or glass used for cell cultures.
Petrogenic: produced by the incomplete combustion of petroleum (e.g. hydrocarbons).
Photon: a particle representing a quantum of light or other electromagnetic
Plasma: A very high-temperature ionized gas composed of electrons and positively
Pleochroism: is the optical phenomenon observed in a mineral that changes its
colour depending on its orientation under polarized light.
Preparatory ground: is the preparatory layer between the support and the paint layer.
Its purpose is mainly to smoothen the surface the paint layer will be applied on. On mural paintings
it is usually composed of slake lime and fine-grained sand.
Proton Induced Gamma-ray Emission (PIGE): PIGE is nuclear analytical technique,
which usually complements PIXE in non-invasive depth profiling of samples. It is based on nuclear
induced by MeV protons, where prompt nuclear gamma-rays are produced. PIGE is particularly
suitable for light element* analysis, such as Li, Be, B, F, Na and Al.
Qualitative: the type of analysis which focuses on the identification of the
elemental* or molecular composition of materials.
Quantitative analysis: the type of analysis that focuses on measuring the quantity
of elements* or compounds* in materials.
Raman band: the peak of a Raman spectrum, that corresponds to a specific scattered
photon and to a certain molecular bond it was scattered by.
Refractive index (n): is a dimensionless measure that describes the way light
propagates through a material compared to its propagation in vacuum. Mathematically it is expressed as:
RI=(Velocity of Light in Vacuum)/(Velocity of Light in a Material)
Sapwood: younger, newly formed outer wood where sap flows, lying between the heartwood
and the cambium*.
Sensitivity: the capability to identify low atomic number elements in a sample matrix.
Semi-quantitative: the type of analysis that gives an approximation of the quantity of
or compounds* in materials.
Spatial resolution: the minimum distance between two independently measured points that
can be distinguished.
Spectrum: of chemical elements* is the radiation energy of an excited element*
visualized in the form of lines or bands, which have characteristic wavelengths for each element*.
Stereomicroscopic examination: is a variant of optical microscopy for low magnification
observation of a sample (typically up to x100 magnification).
Structural integrity: Study of the ability of an item to hold together under a load,
including its own weight, resisting breakage or bending.
Structural methods: Physical methods used to determine of the effects of loads on
materials and their components.
TAQ=Terminus Ante Quem: chronological bound before which an event occurred: In
an architectural context, a fire or a restoration are TAQ to the building since the initial building
occurred before them.
Thermal behaviour: Study of the response of solid materials to the variation of
Thermoremanent magnetization: from thermo: "temperature", and
remanent: "which remains":
magnetization acquired when the temperature falls below a certain temperature (known as the Curie point)
during the cooling. TPQ=Terminus Post Quem: chronological limit after which an event happened.
In an architectural context, the making of the materials or the felling of the trees constitute a TPQ to
the building since they are prior to the building of the masonry structure.
Thin section: a very thin sample cut out of the investigated specimen, ground
optically flat and mounted on a glass slide in order to be examined with an optical microscope.
Trace element: an element* of a sample with concentration lower than 1000 parts per million
Vector: as a force, the EMF can be represented in any spot of the Earth surface by
a vector (an
arrow) which orientation defines the direction and the sense of action of the field and which
length represents its intensity.
Vibrational level: When molecules are excited using UV/visible radiation, an
electron residing in a low-energy atomic or molecular orbital passes to a higher-energy orbital
This transition can only occur when the energy of the UV/vis photon is exactly the same energy as
the energy difference between the 2 orbital energies. Because the electron has to absorb energy to
jump to a higher electronic level, the transition is called “electronic absorption”. But molecules
exhibit 2 additional radiation-induced transition types: vibrational transitions and
transitions. In fact, molecules vibrate and rotate at very specific energies. For each electronic
state, there are many vibrational states. And for each vibrational state, there are many rotational
Wane: rounded corner under/caused by the lack of bark Weight percent or weight -
(wt%): a measure to show the relative proportions
of an element* or compound* to the total weight of the sample . It is a dimensionless size.
X-rays: electromagnetic radiation with a wavelength range of 0.01 – 10 nm.
Z: atomic number, number of protons in an element’s nucleus. It uniquely identifies
A research project by Diadrasis, funded by the J.S Latsis Public Benefit Foundation
The sole responsibility for its contents lies with its authors.