EN 16682:2017

Conservation of cultural heritage - Methods of measurement of moisture content, or water content, in materials constituting immovable cultural heritage

This European Standard is aimed to inform and assist users in the choice and use of the most appropriate method to obtain reliable measurements of the moisture content, or water content, in wood and masonry (including brickwork, stonework, concrete, gypsum, mortars, etc.) in the specific case of the built cultural heritage.
It provides a basic framework to take and interpret this kind of measurements on the above cultural heritage materials that have undergone weathering, pest attack, salt migration or other transformations over time.
It specifies four absolute methods (i.e. gravimetric, Karl Fischer titration, azeotropic distillation and calcium carbide); explains their characteristics, pros and cons, and gives specifications for the transformation of readings into the same unit to make measurements taken with different methods comparable.
It specifies the three principal relative methods (i.e. electrical resistance, capacitance, and relative humidity in equilibrium with the material), pointing out their characteristics and uncertainties when used in the field of cultural heritage.
In addition, it provides an informative overview of ten other relative methods, their characteristics, pros and cons.
It gives specifications for the calibration of the various methods. It also compares the above methods in relation to their accuracy, sampling requirement, sample size, laboratory or field use, and other problems encountered in the field of cultural heritage to prevent instrument misuse, reduce uncertainties and avoid reading misinterpretation.

Erhaltung des kulturellen Erbes - Verfahren zur Bestimmung des Feuchte- bzw. Wassergehalts in Materialien des unbeweglichen kulturellen Erbes

Diese Europäische Norm dient der Information und Unterstützung von Anwendern bei der Auswahl und Anwendung des geeignetsten Verfahrens zur Durchführung verlässlicher Messungen des Feuchte- oder Wassergehalts in Holz und Mauerwerk (einschließlich Ziegel- und Steinmauerwerk, Beton, Gips, Mörtel usw.) speziell des gebauten kulturellen Erbes.
Sie bietet einen grundsätzlichen Rahmen für die Durchführung und Auslegung solcher Messungen an den o. g. Materialien des kulturellen Erbes, die im Laufe der Zeit Verwitterung, Schädlingsbefall, Salzmigration und anderen Veränderungen ausgesetzt waren.
Sie legt vier absolute Verfahren fest (Gravimetrie, Karl-Fischer-Titration, azeotropische Destillation und Calciumcarbidverfahren), erklärt deren Merkmale, Vor- und Nachteile und gibt Vorgaben für die Umrechnung von Ablesewerten in eine gemeinsame Einheit, um mit unterschiedlichen Verfahren gewonnene Messwerte vergleichbar zu machen.
Sie legt die drei hauptsächlichen relativen Verfahren fest (d. h. elektrischer Widerstand, Kapazität und relative Gleichgewichtsfeuchte mit dem Material) und weist dabei auf deren Merkmale und die Unsicherheiten ihrer Anwendung auf dem Gebiet des kulturellen Erbes hin.
Außerdem bietet sie einen informativen Überblick über zehn weitere relative Verfahren, deren Merkmale sowie Vor- und Nachteile.
Sie enthält Spezifikationen für die Kalibrierung der verschiedenen Verfahren. Außerdem vergleicht sie die oben genannten Verfahren bezüglich ihrer Genauigkeit, der Anforderungen an die Probenahme, des Probenumfangs, der Labor- oder Praxisanwendung und anderer Probleme im Zusammenhang mit dem kulturellen Erbe, um den falschen Gebrauch von Messinstrumenten zu verhindern, Unsicherheiten zu reduzieren und die Fehlinterpretation von Ablesewerten zu vermeiden.

Conservation du patrimoine culturel - Méthodes de mesurage de la teneur en humidité, ou teneur en eau, de matériaux constituant un patrimoine culturel immatériel

La présente Norme européenne vise à informer les utilisateurs et à les aider à choisir la méthode qui convient le mieux pour obtenir des mesurages fiables de la teneur en humidité, ou teneur en eau, des structures en bois et de la maçonnerie (y compris les ouvrages en briques ou en pierres, le béton, le gypse, le mortier, etc.) dans le cas particulier du patrimoine culturel bâti.
Elle fournit un cadre de base pour la réalisation et l’interprétation de ce type de mesurages sur les matériaux du patrimoine culturel précédemment cités ayant subi une altération due aux conditions climatiques, à une attaque de parasites, à une migration de sels ou à d’autres transformations survenues au fil du temps.
Elle définit quatre méthodes absolues (à savoir la méthode gravimétrique, le titrage Karl Fischer, la distillation azéotropique et le test à la bombe à carbure), en expliquant leurs caractéristiques, leurs avantages et leurs inconvénients. Elle donne des explications détaillées pour la conversion des mesures dans la même unité afin de permettre la comparaison des mesurages avec les résultats d'autres méthodes.
Elle définit les trois principales méthodes relatives (à savoir la méthode résistive, la méthode capacitive et la méthode de l’humidité relative d’équilibre avec le matériau), en attirant l’attention sur leurs caractéristiques et leurs incertitudes lorsqu’elles sont utilisées dans le domaine du patrimoine culturel.
Elle fournit, en outre, à titre informatif, une description succinte de dix autres méthodes relatives, avec leurs caractéristiques, leurs avantages et leurs inconvénients respectifs.
Elle donne des indications précises concernant l’étalonnage des différentes méthodes. Elle établit également une comparaison entre les méthodes susmentionnées, passant en revue leur exactitude, les exigences en matière d’échantillonnage, la taille des échantillons, l’utilisation en laboratoire ou sur site, ainsi que d’autres problèmes rencontrés dans le domaine du patrimoine culturel, pour empêcher une mauvaise utilisation des instruments, réduire les incertitudes et éviter une mauvaise interprétation des mesures.

Ohranjanje kulturne dediščine - Navodilo za merjenje vsebnosti vlage v materialih sestavov premične in nepremične kulturne dediščine

Ta evropski standard so navodila, ki določajo ustrezne metodologije za merjenje vsebnosti vlage v materialih sestavov premične in nepremične, zunanje ali notranje kulturne dediščine za namene ohranjanja. Namenjen je za pomoč uporabnikom pri izbiri najustreznejšega sistema za pridobivanje zanesljivih meritev za potrebe ohranjanja. Navaja, kako se lahko vsebnost vlage meri neposredno ali posredno, t.j. razlikovanje med brezstičnimi in stičnimi, neinvazivnimi in invazivnimi, neporušitvenimi in porušitvenimi metodologijami, kdaj so metodologije sprejemljive in kdaj niso (z vidika ohranjanja). Prikazane so prednosti in slabosti posameznih merilnih sistemov. Za vsak merilni sistem so predstavljeni negotovosti in dejavniki, ki lahko vplivajo na odčitke in njihovo razlago. Ta evropski standard bo zagotovil nasvete in podporo pri zahtevnejših zadevah.

General Information

• Status: Published
• Publication Date: 28-Feb-2017
• Withdrawal Date: 29-Sep-2017
• ICS: 97.195 - Items of art and handicrafts. Cultural property and heritage
• Technical Committee: CEN/TC 346 - Conservation of cultural property
• Drafting Committee: CEN/TC 346/WG 7 - Specifying and measuring Indoor/outdoor climate
• Current Stage: 9093 - Decision to confirm - Review Enquiry
• Start Date: 15-Nov-2022
• Completion Date: 14-Apr-2025
• Ref Project: SIST EN 16682:2017 - Conservation of Cultural Heritage - Guide to the measurements of moisture content in materials constituting movable and immovable cultural heritage

Overview

EN 16682:2017 - Conservation of Cultural Heritage is a European guide for measuring moisture content (water content) in materials that make up movable and immovable cultural heritage. The standard helps users choose and apply appropriate measurement methods for wood and masonry (brick, stone, concrete, gypsum, mortars, etc.) affected by weathering, pest attack, salt migration or aging. It explains how to obtain reliable, comparable readings and how to interpret results in conservation contexts.

Key Topics and Requirements

• Scope and definitions: clear distinction between moisture content and water content, and between gravimetric (mass-based) and volumetric modes.
• Absolute methods (specified):
  • Gravimetric (oven or alternative drying procedures)
  • Karl Fischer titration (volumetric, coulometric, oven-vaporization variants)
  • Azeotropic distillation
  • Calcium carbide test
    The standard explains characteristics, pros/cons and procedures for each absolute method.
• Relative methods (specified):
  • Electrical resistance / conductance
  • Capacitance / dielectric methods
  • Relative humidity in equilibrium with the material (drilled cavity, external sealed box)
    The document also provides an informative overview of ten other relative techniques (e.g., microwave, evanescent-field dielectrometry, time-domain reflectometry, NMR, near-infrared spectroscopy, ultrasound, thermography).
• Calibration and comparability: procedures to calibrate instruments, transform readings into common units, and reduce measurement uncertainty so results from different methods are comparable.
• Sampling and handling: guidance on sampling strategy, sample size, and handling for both laboratory and field work to avoid misuse and misinterpretation.
• Performance comparison: assessment of accuracy, sampling requirements, laboratory vs. field suitability, and typical problems encountered in built heritage.

Practical Applications and Users

EN 16682:2017 is intended for:

• Conservators and conservation scientists conducting condition assessments and treatment planning.
• Heritage engineers and building surveyors diagnosing moisture-related decay, salt migration and structural risks.
• Analytical laboratories selecting appropriate absolute measurement techniques.
• Facilities managers and contractors monitoring moisture during conservation, restoration or environmental control work.

Common uses include moisture mapping, monitoring drying treatments, checking compatibility of repair materials, and supporting decisions about ventilation, dehumidification or remedial interventions.

Related Standards (if applicable)

The standard recommends using existing European standards for modern building materials where appropriate and aligns methods and terminology to enable interoperability with other EN guidance on building materials and moisture measurement. For project-specific work, consult relevant EN standards and national norms that address sampling, laboratory methods and instrument calibration.

Standards Content (Sample)

SLOVENSKI STANDARD
01-maj-2017
2KUDQMDQMHNXOWXUQHGHGLãþLQH1DYRGLOR]DPHUMHQMHYVHEQRVWLYODJHYPDWHULDOLK
VHVWDYRYSUHPLþQHLQQHSUHPLþQHNXOWXUQHGHGLãþLQH
Conservation of Cultural Heritage - Guide to the measurements of moisture content in
materials constituting movable and immovable cultural heritage
Erhaltung des kulturellen Erbes - Leitfaden zu Messungen des Feuchtegehalts in
Materialien des beweglichen und unbeweglichen kulturellen Erbes
Conservation du patrimoine culturel - Guide relatif aux mesures de la teneur en eau de
matériaux constituant un patrimoine culturel matériel et immatériel
Ta slovenski standard je istoveten z: EN 16682:2017
ICS:
97.195 8PHWQLãNLLQREUWQLãNLL]GHONL Items of art and handicrafts.
.XOWXUQHGREULQHLQNXOWXUQD Cultural property and
GHGLãþLQD heritage
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 16682
EUROPEAN STANDARD
NORME EUROPÉENNE
March 2017
EUROPÄISCHE NORM
ICS 97.195
English Version
Conservation of cultural heritage - Methods of
measurement of moisture content, or water content, in
materials constituting immovable cultural heritage
Conservation du patrimoine culturel - Méthodes de Erhaltung des kulturellen Erbes - Verfahren zur
mesurage de la teneur en humidité, ou teneur en eau, Bestimmung des Feuchte- bzw. Wassergehalts in
de matériaux constituant un patrimoine culturel Materialien des unbeweglichen kulturellen Erbes
immatériel
This European Standard was approved by CEN on 25 December 2016.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 16682:2017 E
worldwide for CEN national Members.

Contents Page
European foreword . 5
Introduction . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 8
4 Symbols and abbreviations . 13
5 Moisture and water content in materials . 14
5.1 Moisture content . 14
5.1.1 General . 14
5.1.2 Dry versus wet mode . 14
5.1.3 Gravimetric versus volumetric mode . 15
5.2 Water content . 15
5.3 Comparison between moisture content and water content . 15
6 Absolute and relative methods . 16
6.1 Absolute methods . 16
6.2 Relative methods . 16
6.3 Comparison between absolute and relative methods . 17
7 Taking and handling samples . 18
8 Calibration . 18
8.1 General . 18
8.2 Instrument calibration . 19
8.2.1 General . 19
8.2.2 Calibration for moisture content . 19
8.2.3 Calibration for water content . 19
8.3 Reproducibility . 19
8.3.1 Instruments for absolute measurements . 19
8.3.2 Instruments for relative measurements . 19
8.3.3 Comparison between absolute and relative methods . 19
9 Use of existing European Standards concerning modern building materials . 20
10 Test report . 20
Annex A (normative) Absolute methods . 22
A.1 Generalities . 22
A.2 Gravimetric method . 22
A.2.1 General . 22
A.2.2 Apparatus . 23
A.2.3 Procedure. 23
A.3 Drying procedures in the gravimetric method. 23
A.3.1 General . 23
A.3.2 Oven drying . 24
A.3.2.1 General . 24
A.3.2.2 Apparatus . 24
A.3.2.3 Drying procedure . 24
A.3.3 Vacuum drying . 25
A.3.3.1 General . 25
A.3.3.2 Apparatus . 25
A.3.3.3 Drying procedure . 25
A.3.4 Compressed-air drying . 25
A.3.4.1 General . 25
A.3.4.2 Apparatus . 25
A.3.4.3 Drying procedure . 26
A.3.5 Adsorption drying . 26
A.3.5.1 General . 26
A.3.5.2 Apparatus . 26
A.3.5.3 Drying procedure . 26
A.3.6 Thermo-gravimetric analysis (TGA) . 27
A.3.6.1 General . 27
A.3.6.2 Apparatus . 27
A.3.6.3 Procedure . 27
A.4 Karl Fischer titration . 28
A.4.1 General . 28
A.4.2 Apparatus . 28
A.4.3 Procedure . 29
A.4.4 Volumetric KF titration (V-KFT) . 30
A.4.4.1 General . 30
A.4.4.2 Apparatus . 30
A.4.4.3 Procedure . 30
A.4.5 Coulometric KF titration (C-KFT). 31
A.4.5.1 General . 31
A.4.5.2 Apparatus . 31
A.4.5.3 Procedure . 31
A.4.6 Oven-vaporization KF titration (OV-KFT) . 32
A.4.6.1 General . 32
A.4.6.2 Apparatus . 32
A.4.6.3 Temperature . 32
A.4.7 KF titration of selected materials . 33
A.5 Azeotropic distillation . 34
A.5.1 General . 34
A.5.2 Apparatus . 34
A.5.3 Procedure. 35
A.6 Calcium carbide test . 35
A.6.1 General . 35
A.6.2 Apparatus . 36
A.6.3 Procedure. 36
Annex B (normative) Relative methods . 41
B.1 Generalities . 41
B.2 Electrical resistance (conductance) . 41
B.3 Capacitance (dielectric) . 42
B.4 Relative humidity in equilibrium with the material . 43
B.4.1 General . 43
B.4.2 Drilled cavity . 43
B.4.3 External sealed box (ESB) . 44
B.4.4 Apparatus . 44
B.4.5 Procedure. 44
Annex C (informative) Other relative methods . 49
C.1 Generalities . 49
C.2 Microwave . 49
C.3 Evanescent-field dielectrometry . 50
C.4 Time-domain reflectometry . 50
C.5 Nuclear magnetic resonance . 51
C.6 Near-infrared spectroscopy (NIRS) . 51
C.7 Ultrasound pulses . 52
C.8 Thermography . 52
Annex D (informative) Methods with special safety requirements . 57
D.1 Generalities . 57
D.2 X-ray . 57
D.3 Gamma rays . 58
D.4 Neutron scattering . 58
Bibliography . 61
European foreword
This document (EN 16682:2017) has been prepared by Technical Committee CEN/TC 346
“Conservation of Cultural Heritage”, the secretariat of which is held by UNI.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by September 2017, and conflicting national standards
shall be withdrawn at the latest by September 2017.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
Introduction
The specific field of cultural heritage is characterized by particular needs and in most cases the existing
standards devised for normal materials cannot be applied. The moisture content, or the water content,
in materials is of primary relevance for the preservation of cultural heritage. High content can be very
damaging (e.g. salt dissolution and mobilization, fungal infestation, corrosion, swelling) as well as low
content (e.g. salt crystallization, shrinkage, wood cracking) or alternating high/low content. It is
therefore important to determine and control this variable to assess the risk of damage and take
preventive conservation measures.
Different methods exist to measure moisture content, or water content, in modern building materials,
based on different physical or chemical principles but most of them are not applicable to cultural
heritage and need to be adapted to this aim.
Generally, non-destructive methods are recommended but their accuracy may be limited. In turn, the
most accurate methods require sampling and can only exceptionally be used. Readings taken with non-
destructive methods may not be comparable especially because they are expressed in different units.
The interpretation of measurements may be obscured by a number of factors (e.g. material, salts,
temperature) to which the methods are subject.
This European Standard considers and specifies characteristics, operative methodologies, pros and cons
of all methods of measurements and establishes a uniform presentation of data and units. It is
addressed to anyone who needs to measure or interpret readings of moisture content, or water content,
in building materials (particularly masonry and wood), and in general to whoever is responsible for the
preservation and maintenance of heritage buildings.
1 Scope
This European Standard is aimed to inform and assist users in the choice and use of the most
appropriate method to obtain reliable measurements of the moisture content, or water content, in
wood and masonry (including brickwork, stonework, concrete, gypsum, mortars, etc.) in the specific
case of the built cultural heritage.
It provides a basic framework to take and interpret this kind of measurements on the above cultural
heritage materials that have undergone weathering, pest attack, salt migration or other transformations
over time.
It specifies four absolute methods (i.e. gravimetric, Karl Fischer titration, azeotropic distillation and
calcium carbide); explains their characteristics, pros and cons, and gives specifications for the
transformation of readings into the same unit to make measurements taken with different methods
comparable.
It specifies the three principal relative methods (i.e. electrical resistance, capacitance, and relative
humidity in equilibrium with the material), pointing out their characteristics and uncertainties when
used in the field of cultural heritage.
In addition, it provides an informative overview of ten other relative methods, their characteristics,
pros and cons.
It gives specifications for the calibration of the various methods. It also compares the above methods in
relation to their accuracy, sampling requirement, sample size, laboratory or field use, and other
problems encountered in the field of cultural heritage to prevent instrument misuse, reduce
uncertainties and avoid reading misinterpretation.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
EN ISO 374-1, Protective gloves against chemicals and micro-organisms - Part 1: Terminology and
performance requirements
EN 420:2003+A1:2009, Protective gloves - General requirements and test methods
EN 455-1:2000, Medical gloves for single use - Part 1: Requirements and testing for freedom from holes
EN 772-10:1999, Methods of test for masonry units - Part 10: Determination of moisture content of
calcium silicate and autoclaved aerated concrete units
EN 837-1:1996, Pressure gauges - Part 1: Bourdon tube pressure gauges - Dimensions, metrology,
requirements and testing
EN 1428:2012, Bitumen and bituminous binders - Determination of water content in bituminous
emulsions - Azeotropic distillation method
EN 13183-1:2002, Moisture content of a piece of sawn timber - Part 1: Determination by oven dry method
EN 13183-2:2002, Moisture content of a piece of sawn timber - Part 2: Estimation by electrical resistance
method
EN 13183-3:2005, Moisture content of a piece of sawn timber - Part 3: Estimation by capacitance method
EN 15758:2010, Conservation of Cultural Property - Procedures and instruments for measuring
temperatures of the air and the surfaces of objects
EN 15898:2011, Conservation of cultural property - Main general terms and definitions
EN 16085:2012, Conservation of Cultural property - Methodology for sampling from materials of cultural
property - General rules
EN 16096:2012, Conservation of cultural property - Condition survey and report of built cultural heritage
EN 16242:2012, Conservation of cultural heritage - Procedures and instruments for measuring humidity
in the air and moisture exchanges between air and cultural property
EN ISO 10304-1:2009, Water quality - Determination of dissolved anions by liquid chromatography of
ions - Part 1: Determination of bromide, chloride, fluoride, nitrate, nitrite, phosphate and sulfate (ISO
10304-1:2007)
EN ISO 11461:2014, Soil quality - Determination of soil water content as a volume fraction using coring
sleeves - Gravimetric method (ISO 11461:2001)
EN ISO 13130:2011, Laboratory glassware - Desiccators (ISO 13130:2011)
EN ISO 14911:1999, Water quality - Determination of dissolved Li+, Na+, NH4+, K+, Mn2+, Ca2+, Mg2+,
Sr2+ and Ba2+ using ion chromatography - Method for water and waste water (ISO 14911:1998)
EN ISO 15512, Plastics - Determination of water content (ISO 15512)
ISO 760:1978, Determination of water — Karl Fischer method (General method)
ISO 3567:2011, Vacuum gauges — Calibration by direct comparison with a reference gauge
ISO 5272:1979, Toluene for industrial use — Specifications
ISO 5280:1979, Xylene for industrial use — Specification
ISO 7183:2007, Compressed-air dryers — Specifications and testing
ISO 11465:1993, Soil quality — Determination of dry matter and water content on a mass basis —
Gravimetric method
ISO 16979:2003, Wood-based panels — Determination of moisture content
ISO Guide 34:2009, General requirements for the competence of reference material producers
ISO/IEC Guide 98-3:2008, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty
in measurement (GUM:1995)
EN ISO/IEC 17025:2005, General requirements for the competence of testing and calibration laboratories
(ISO/IEC 17025:2005)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 15898:2011 and the following
apply.
3.1
absolute method/measurement
measuring method whose readings can be expressed in terms of SI units
3.2
active sensor
sensor that needs some electrical power supply to operate
3.3
atmospheric pressure
barometric pressure
pressure is the force per unit area exerted by the air column above the measuring point
Note 1 to entry: This is expressed in hPa (hectopascal).
[SOURCE: EN 16242:2012, 3.2]
3.4
bound water
in masonry: water molecules physically or chemically bound to the material; bound water cannot
dissolve soluble substances. In wood: water bonded in the cell walls; it is responsible for
shrinkage/swelling
3.5
crystallization water
hydration water
water molecules that are part of a hydrated crystal or molecule
3.6
desiccator
equipment in which a desiccant is used to maintain the air as close as possible to the absolutely dry
condition
[SOURCE: EN 322:1993, 4.3]
3.7
desiccant drying
method in which drying is obtained with a continuous flow of dry air (from compressed air), or with
moisture absorption from a highly hygroscopic substance used as desiccant
[SOURCE: EN 322:1993, 4.3]
3.8
destructive
causing destruction or damage to cultural heritage materials
3.9
dew-point hygrometer
instrument for measuring the temperature at which a cooled parcel of air becomes saturated with
water vapour
[SOURCE: EN 16242:2012, 3.4]
3.10
dew-point temperature
temperature to which air is cooled at constant pressure and constant water vapour content in order for
saturation to occur
Note 1 to entry: This is expressed in degrees Celsius (°C).
[SOURCE: EN 15758:2010, 3.6]
3.11
dry air
atmospheric air without water vapour
[SOURCE: EN 16242:2012, 3.6]
3.12
dry matter
whole of the substances which do not volatilize under the conditions of drying specified in this standard
[SOURCE: ISO 1026:1982, 2.1]
3.13
equilibrium moisture content
EMC
moisture content at which a material neither loses nor gains moisture from the surrounding
atmosphere at given relative humidity and temperature levels
Note 1 to entry: This is expressed in g/kg as the ratio of the mass of water contained in the material and the dry
mass of the same material.
[SOURCE: EN 16242:2012, 3.8]
3.14
external sealed box
ESB
box with five thermally insulating and impermeable faces and one missing face, fixed to the surface of a
material to create an air pocket in hygrometric equilibrium with the material
3.15
fibre saturation point
moisture content at which no free water is present in wood, while the cell walls are saturated with
bound water
3.16
free water
in masonry: liquid water inside pores. In wood: water contained in the cell cavities. It can dissolve
soluble substances
3.17
hygrometer
instrument measuring relative humidity
Note 1 to entry: It generally comprises a sensor, which is set in equilibrium with the air, and a system that
transforms the signal from the sensor into humidity readings.
[SOURCE: EN 16242:2012, 3.11]
3.18
invasive
requiring the entry of a probe, or other instrument into a cultural heritage material, for diagnostic
purposes
3.19
irreversible relative humidity sensor
sensor in which reached relative humidity levels remain permanently marked
3.20
minimally destructive
minimally invasive
damage caused, or the sample taken, are very small and not easily recognizable, so that it can be
considered acceptable, or justified in view of the advantages expected from the analysis
3.21
moisture content
MC
amount of water in the material, as determined in accordance with a gravimetric method specified in
this European Standard; the method may include the volatile organic compounds that may be lost when
the material is heated at moderate temperatures
Note 1 to entry: The MC is expressed as a mass fraction in percent (%).
3.22
oven drying
drying method obtained with a ventilated oven at temperature 103°C ± 2°C
[SOURCE: EN 322:1993, 4.2]
3.23
passive sensor
sensor that does not need any electrical power supply to operate
3.24
proxy
material or a specimen that is a substitute or a replacement for something else, under the assumption of
identical behaviour of the material under investigation
3.25
relative humidity
RH
ratio of the actual vapour pressure of the air to the saturation vapour pressure
Note 1 to entry: The RH is expressed in percent (%).
[SOURCE: EN 15757:2010, 3.9]
3.26
relative method
relative measurement
measuring method whose readings cannot be expressed in terms of SI units and should be expressed in
relation to something else, kept as a reference
Note 1 to entry: The scale depends on the specific choice of the reference; it can also be expressed as a fraction
of a given value.
3.27
sample
portion of material, ideally representative, removed from the cultural property for scientific
investigation
[SOURCE: EN 16085:2012, 3.2]
3.28
temperature
temperature read on a thermometer which is exposed to air in a position sheltered from direct solar
radiation or other energy sources
Note 1 to entry: The temperature is expressed in degrees Celsius (°C).
[SOURCE: EN 15758:2010, 3.1]
3.29
thermometer
instrument to measure temperature which comprises a sensor which is placed in thermal equilibrium
with the air (if it measures the air temperature) or the surface, sometimes a probe that contains and
protects the sensor, and a system that transforms the input from the sensor into an output expressed in
degrees Celsius (°C)
[SOURCE: EN 15758:2010, 3.20]
3.30
vacuum drying
drying method obtained by vacuum pumping to lower the atmospheric pressure to 4 ± 2 hPa in the
drying chamber
3.31
vacuum gauge
instrument for measuring gas or vapour pressures that are less than the prevailing atmospheric
pressure
[SOURCE: ISO 3529-3:2014, 2.1.2]
3.32
water content
WC
amount of water in the material, as determined in accordance with the Karl Fisher titration specified in
this European Standard; this method may include crystallization water
Note 1 to entry: The WC is expressed as a mass fraction in percent (%).
4 Symbols and abbreviations
EFD Evanescent-Field Dielectrometry
EMC Equilibrium Moisture Content
ESB External Sealed Box
IAEA International Atomic Energy Agency, Vienna
KF Karl Fischer
KFT Karl Fischer titration
C-KFT coulometric KFT
V-KFT volumetric KFT
MC Moisture Content expressed on dry basis
MC Moisture Content expressed on wet basis
w
NIR Near Infrared
NIRS Near Infrared Spectroscopy
NMR Nuclear Magnetic Resonance
OV-KFT Oven-vaporization KF titration
C-OV-KFT coulometric oven-vaporization KF titration
V-OV-KFT volumetric oven-vaporization KF titration
RH Relative Humidity
SI units International System of units
SRXTM Synchrotron-based X-ray Tomographic Microscopy
TDR Time-Domain Reflectometry
TGA Thermogravimetric Analysis
VOC volatile organic compounds
WC Water content expressed on dry basis
WC Water content expressed on wet basis
W
ε dielectric constant
m initial (moist) mass of the test sample
H
m mass of the sample after drying
m mass of water extracted from the sample
w
5 Moisture and water content in materials
5.1 Moisture content
5.1.1 General
The moisture content (MC) is defined as the ratio between the mass of the water extracted from a
material sample and the mass of the dry sample expressed in percent (%), i.e.
m mm−
wH 0
MC= ×=100 × 100 (1)
mm
where m is the initial mass of the moist sample, m the mass of the sample after it has been dried, and
H 0
m = m - m the mass of water extracted from the sample (ISO 16979:2003, EN 13183-1:2002,
w H 0
EN 772-10:1999 and EN ISO 11461:2014). MC ranges from 0 (completely dry sample) to a value
determined by the material’s porosity at saturation.
The MC is specifically measured by gravimetry (ISO 16979:2003) or other methods that comply with
the basic Formula (1). From the practical point of view, the oven-drying method assumed as a reference
1)
may include volatile organic compounds (VOC) that may be released when the material is heated at
moderate oven temperatures.
The MC is expressed as a ratio of homogeneous quantities and for this reason it is independent of the
unit used to express m and m . However, in the measuring report the use of the SI unit for mass (i.e. g)
H 0
is recommended. The moisture content shall be reported to the nearest 0,1 % stating that it is by dry
weight.
5.1.2 Dry versus wet mode
The MC defined in Formula (1) is expressed on dry basis, i.e. is referred to the mass m of the sample
after it has been dried (e.g. using the gravimetric method in A.2). Other methods exist (e.g. azeotropic
distillation in A.5, calcium carbide test in A.6) that allow a direct determination of m and m but
H w
destroy the sample so that it is impossible to determine m with a balance. For these methods the
moisture content is usually expressed on wet basis (MC ) taking the mass of the moist sample m as a
w H
reference, i.e.:
m
w
MC × 100 (2)
w
m
H
Of course MC > MC . The difference between MC and MC makes the comparison between readings
w w
obscure. For clarification, this standard recomends the use of the MC on dry basis for all methods.
When a method destroys samples, one of the two following options shall be used:
Option 1: Calculate m0 = mH - mw and proceed with Formula (1).
Option 2: Determine MC on wet basis, i.e. Formula (2), and then apply the transformation to dry basis
w
by using Formula (3) that relates MC to MC :
w
 
MC
w
  (3)
MC × 100
 
100− MC
 w
The inverse relationship is
1)
Gases produced by decomposition, reduction and/or other chemical reactions should be excluded.
=
=
 
MC
MC × 100 (4)
 
w
100+ MC
 
5.1.3 Gravimetric versus volumetric mode
When the MC is measured, it can be expressed as a percentage of the sample, as follows:
a) gravimetric mode, i.e. the MC is the ratio between the mass of the removed water and the mass of
the dried sample (dry basis) or the moist sample (wet basis). The result is expressed in % by mass.
b) volumetric mode, i.e. the MC is the ratio between the volume of the removed water (its mass in g
equals the volume in cm ) and the actual volume of the moist sample. The result is expressed in %
by volume.
In order to avoid confusion, it is necessary to specify if the percentage is derived from gravimetric or
volumetric determinations. The gravimetric mode is independent from the presence of voids or
gradients; the volumetric mode varies with the material density and presence of voids. This is a
problem when the material density is not homogeneous. It may vary from point to point (e.g. for
deterioration, pests or voids) or change over time, as typically occurs in cultural heritage materials.
5.2 Water content
The water content (WC) consists of all kinds of water present in a material, i.e. free water, bound water
and crystallization water, but excludes VOC.
WC is measured by Karl Fischer titration (A.4) that is specific for water (e.g. free water, bound water,
crystallization water) (ISO 760:1978).
Although the common use is to express the water content in terms of wet basis, this standard
recommends the use of the WC on dry basis for homogeneity reasons, to make comparable the readings
with other methods. The WC shall be expressed in terms of dry basis as specified for MC in the previous
clause, but substituting WC to MC.
5.3 Comparison between moisture content and water content
When the sample includes VOC or crystallization water in hydrated minerals, the loss of mass after
drying is not only due to moisture. The difference in readings when different methods are used may be
determined by the presence of VOC or crystallization water (both apparently increase the evaluation of
m extracted from the sample), the sensitivity of the measuring method to these factors and the
w
operating temperature. One should have clear understanding which type of water is detected and what
is the purpose of the measurements: e.g. MC: moisture exchangeable with the environment (wood
shrinkage/swelling; soluble salt mobilization, mould), or WC: the total water content including
crystallization water. In some cases it is possible to calculate the difference to compare results or to
remove the contribution of VOC or crystallization water. In another cases a precise determination of WC
may be preferable to a method specific for MC (or vice-versa) because smaller samples are required.
The situation is more complex in the case of electromagnetic forces (e.g. capacitance) or where a
microwave beam penetrates inside a material (e.g. microwave, evanescent-field dielectrometry, time-
domain reflectometry). The electromagnetic forces or the microwave beam will interact with the H O
molecules because of their polar structure. However, the interaction is different if the water molecule is
part of the material structure (e.g. cellulose chain, crystallization water) or is free to respond to the
excitation. As a consequence, all H O molecules will respond to the signal, but the strongly bound H O
2 2
molecules will respond more weakly, and the free moisture will respond more strongly. In such a case
the instrument reading interpretation is not straightforward.
In the following guidelines MC or WC will represent the amount of water available in a moist sample
which can be extracted and measured with one of the measurement methods specified in this standard.
=
In order to assist the user, each method will specify whether it measures MC or WC, in case this may be
relevant. Such methods are considered “absolute” because the readings they provide are representative
of the MC, or the WC, and do not depend on anything else (except for observational uncertainties).
When a measurement method cannot be calibrated with a suitable reference standard, the absolute
value of the MC (or the WC) remains unknown, but it may be useful to make relative comparisons from
one measurement point (at a given time) to another measurement point (at subsequent times) to detect
gradients in space or time. Such methods are considered to provide “relative” readings.
6 Absolute and relative methods
6.1 Absolute methods
Absolute methods are measuring
...