Conservation of cultural heritage - Procedure for the analytical evaluation to select cleaning methods for porous inorganic materials used in cultural heritage

This document gives the test methodology for evaluation of both harmfulness and effectiveness of a cleaning method as applied to porous inorganic materials. These include materials such as natural or artificial stone, included those with painting layers as finishes. Evaluation admits the use of on site instrumental analyses and the taking of samples to be studied in laboratory.
Harmfulness evaluation has a priority over the effectiveness.
This document applies to:
a)   all methods of cleaning, which have characteristics of parameterization and reproducibility (see EN 17138:2018). Part A;
b)   all new methods that are under development. Part B.
This document applies to evaluate the optimum methods for cleaning and the optimization of the parameters of the selected cleaning process.

Erhaltung des kulturellen Erbes - Methodologie für die analytische Prüfung zur Auswahl von Reinigungsverfahren von porösen anorganischen Objekten des kulturellen Erbes

Dieses Dokument enthält das Prüfverfahren zur Bewertung der Schädlichkeit sowie auch der Wirksamkeit eines Reinigungsverfahrens, das auf porösen anorganischen Materialien angewendet wird. Dazu zählen Materialien wie beispielsweise Naturstein oder künstlicher Stein einschließlich solcher Steine mit Farbschichten auf den Oberflächen. Die Bewertung gestattet die instrumentelle Analytik und die Probenahme vor Ort; diese Proben werden später im Labor untersucht.
Die Bewertung der Schädlichkeit hat Vorrang vor der Bewertung der Wirksamkeit.
Dieses Dokument gilt für:
a)   alle Reinigungsverfahren, die Merkmale der Parametrisierung und Reproduzierbarkeit aufweisen (siehe EN 17138:2018) - Teil A;
b)   alle neuartigen Verfahren, die sich in der Entwicklung befinden - Teil B.
Dieses Dokument dient der Bewertung der optimalen Reinigungsverfahren und der Optimierung der Parameter von ausgewählten Reinigungsprozessen.

Conservation du patrimoine culturel - Procédure pour l'évaluation analytique et le choix des méthodes de nettoyage des matériaux inorganiques poreux dans les bâtiments d'intérêt patrimonial

Le présent document présente la méthodologie d'essai utilisée pour l'évaluation de la dangerosité et de l'efficacité d'une méthode de nettoyage appliquée aux matériaux inorganiques poreux. Il s'agit de matériaux comme la pierre naturelle ou artificielle, y compris ceux recouverts de couches de peinture de finition. L'évaluation admet le recours à des analyses instrumentales sur site et le prélèvement d'échantillons à étudier en laboratoire.
L'évaluation de la dangerosité prime sur l'efficacité.
Le présent document s’applique à :
a)   toutes les méthodes de nettoyage présentant des caractéristiques de paramétrage et de reproductibilité. (voir l’EN 17138:2018). Partie A ;
b)   toutes les nouvelles méthodes en cours de développement. Partie B.
Le présent document s’applique à l’évaluation des meilleures méthodes de nettoyage ainsi que l'optimisation des paramètres du processus de nettoyage choisi.

Ohranjanje kulturne dediščine - Postopek za analitično vrednotenje pri izbiri metod za čiščenje poroznih anorganskih materialov, uporabljenih pri tej kulturni dediščini

General Information

Status
Published
Public Enquiry End Date
31-Aug-2020
Publication Date
22-Jul-2021
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
21-Jul-2021
Due Date
25-Sep-2021
Completion Date
23-Jul-2021

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SLOVENSKI STANDARD
SIST EN 17488:2021
01-september-2021
Ohranjanje kulturne dediščine - Postopek za analitično vrednotenje pri izbiri
metod za čiščenje poroznih anorganskih materialov, uporabljenih pri tej kulturni
dediščini

Conservation of cultural heritage - Procedure for the analytical evaluation to select

cleaning methods for porous inorganic materials used in cultural heritage

Erhaltung des kulturellen Erbes - Methodologie für die analytische Prüfung zur Auswahl

von Reinigungsverfahren von porösen anorganischen Objekten des kulturellen Erbes

Conservation du patrimoine culturel - Procédure pour l'évaluation analytique et le choix

des méthodes de nettoyage des matériaux inorganiques poreux dans les bâtiments
d'intérêt patrimonial
Ta slovenski standard je istoveten z: EN 17488:2021
ICS:
97.195 Umetniški in obrtniški izdelki. Items of art and handicrafts.
Kulturne dobrine in kulturna Cultural property and
dediščina heritage
SIST EN 17488:2021 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 17488:2021
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SIST EN 17488:2021
EN 17488
EUROPEAN STANDARD
NORME EUROPÉENNE
June 2021
EUROPÄISCHE NORM
ICS 97.195
English Version
Conservation of cultural heritage - Procedure for the
analytical evaluation to select cleaning methods for porous
inorganic materials used in cultural heritage

Conservation du patrimoine culturel - Procédure pour Erhaltung des kulturellen Erbes - Methodologie für die

l'évaluation analytique et le choix des méthodes de analytische Prüfung zur Auswahl von

nettoyage des matériaux inorganiques poreux dans les Reinigungsverfahren von porösen anorganischen

bâtiments d'intérêt patrimonial Objekten des kulturellen Erbes
This European Standard was approved by CEN on 23 May 2021.

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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,

Poland, Portugal, Republic of North Macedonia, 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: Rue de la Science 23, B-1040 Brussels

© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 17488:2021 E

worldwide for CEN national Members.
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SIST EN 17488:2021
EN 17488:2021 (E)
Contents Page

European foreword ....................................................................................................................................................... 4

Introduction .................................................................................................................................................................... 5

1 Scope .................................................................................................................................................................... 7

2 Normative references .................................................................................................................................... 7

3 Terms and definitions ................................................................................................................................... 8

4 Abbrevations..................................................................................................................................................... 9

5 General procedure (Part A) ......................................................................................................................... 9

5.1 Overview ............................................................................................................................................................ 9

5.2 Identification of substrate and characterization of unwanted materials................................ 10

5.3 Selection of suitable cleaning methods to be tested ........................................................................ 11

5.4 Localization, delimitation and numbering of the cleaning trial areas ...................................... 11

5.5 Design of the evaluation procedure and definition of a referenced cleaned area ............... 12

6 On site surface investigations .................................................................................................................. 15

6.1 Optical observation ..................................................................................................................................... 15

6.1.1 Portable digital microscope ..................................................................................................................... 15

6.1.2 Raking light .................................................................................................................................................... 15

6.1.3 Portable digital stereo microscope ....................................................................................................... 15

6.1.4 Fluorescence induced by UV radiation ................................................................................................. 15

6.2 Chemical/physical analysis ...................................................................................................................... 16

6.2.1 Measurement of colour .............................................................................................................................. 16

6.2.2 Elemental analysis by portable XRF ...................................................................................................... 16

6.2.3 Molecular analysis by portable FTIR .................................................................................................... 16

6.2.4 Surface ion analysis ..................................................................................................................................... 16

6.3 Water absorption assessment ................................................................................................................. 17

6.3.1 General ............................................................................................................................................................. 17

6.3.2 Determination of water absorption by pipe method (in situ) ..................................................... 17

6.3.3 Determination of water absorption by contact sponge method (in situ) ................................ 17

6.3.4 Water drop test (in situ) ............................................................................................................................ 17

7 Laboratory analysis on samples taken from trial areas ................................................................ 18

7.1 General ............................................................................................................................................................. 18

7.2 Sampling .......................................................................................................................................................... 18

7.3 Chemical/physical analysis ...................................................................................................................... 19

7.3.1 Examinations of fragments surfaces by TLOM, RLOM, SEM/ESEM and EDS

microanalysis ................................................................................................................................................ 19

7.3.2 Examinations of thin and polished and cross section by TLOM, RLOM, SEM/ESEM and

EDS microanalysis ........................................................................................................................................ 20

7.3.3 Vibrational spectroscopy (FTIR, micro-FTIR and Raman) ............................................................ 20

7.4 Surface morphology analysis ................................................................................................................... 20

7.4.1 Measurement of roughness (see ISO 25178) ..................................................................................... 20

7.5 Wet chemical analysis (on aqueous extract) in the case of chemical cleaning ...................... 21

7.5.1 Extraction procedure .................................................................................................................................. 21

7.5.2 Analysis on aqueous extract ..................................................................................................................... 23

8 Overall evaluation of results obtained ................................................................................................. 23

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SIST EN 17488:2021
EN 17488:2021 (E)
9 Analytical procedure for testing methods under development on specimens of

analogous material (Part B)...................................................................................................................... 24

9.1 General procedure ....................................................................................................................................... 24

9.2 Preparation of test specimens ................................................................................................................. 26

9.2.1 Number and dimensions of test specimens ........................................................................................ 26

9.2.2 Pre-conditioning of test specimens ........................................................................................................ 27

9.3 Evaluation process of the cleaning method(s) under test ............................................................. 27

9.4 Test analysis on specimens before and after the application of cleaning methods ............. 27

9.4.1 General ............................................................................................................................................................. 27

9.4.2 Determination of water absorption by capillarity ........................................................................... 27

9.4.3 Colour measurement of surfaces ............................................................................................................ 28

9.4.4 Observation of the surfaces by the stereo microscope ................................................................... 28

9.4.5 Determination of mass variation ............................................................................................................ 28

9.4.6 Thin and polished cross sections analysis by TLOM, RLOM, SEM/ESEM-EDS ......................... 28

9.4.7 Thin and polished cross sections analysis by TLOM, RLOM, SEM/ESEM-EDS on

fragments of surfaces .................................................................................................................................. 29

9.4.8 Cleaning application .................................................................................................................................... 29

9.5 Analysis of aqueous extract for chemical cleaning ........................................................................... 30

9.6 Test report ...................................................................................................................................................... 30

9.6.1 General information .................................................................................................................................... 30

9.6.2 Results of measurements on specimens .............................................................................................. 30

Annex A (normative) Examples of trial applications .................................................................................... 33

Annex B (informative) Test carried out, findings, inference ..................................................................... 38

Annex C (informative) Specifications to be reported for different cleaning methods (see

EN 17138:2018) ............................................................................................................................................ 48

Bibliography ................................................................................................................................................................. 52

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SIST EN 17488:2021
EN 17488:2021 (E)
European foreword

This document (EN 17488:2021) 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 December 2021, and conflicting national standards shall

be withdrawn at the latest by December 2021.

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 organisations of the

following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia,

Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland,

Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North

Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United

Kingdom.
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SIST EN 17488:2021
EN 17488:2021 (E)
Introduction

Cleaning is the removal of unwanted material from an object surface or near-surface.

A cultural heritage object is irreplaceable and while cleaning is undertaken for object conservation, its

effects are irreversible. Failure to consider and address the technical problems which can arise during

cleaning may cause irrevocable damage to an object. Cultural heritage should be cleaned using the least

disruptive/invasive procedure possible in order to best preserve it.

Furthermore, an inadequate or inappropriate intervention may cause, or increase, future deterioration

processes or eliminate materials which are undocumented or which would allow a greater understanding

of the history of an object.

The actions required for cleaning involve a degree of risk for the object and therefore demand extreme

caution. The chosen methods for cleaning should not be harmful to the object, the operator, the

surroundings /environment, or users of the site.

Cleaning operation needs to take into account the compatibility definition (EN 15898) as the “extent to

which one material can be used with another material without putting significance or stability at risk”.

Extending the definition of compatibility to the cleaning action a “compatibility analysis” should therefore

ascertain how cleaning actions (in terms of effectiveness and harmfulness) would impact on the

significance and stability of the heritage object.

A successful cleaning strategy needs to adher to the strategy for the whole conservation-project in

accordance with the conservation-process and the condition report (EN 16853, EN 16085 and EN 16095)

and requires careful consideration of a number of aspects which include but are not limited to:

— the significance of the object;
— the aim of the cleaning;

— a clear definition of the nature of the materials to be removed and the rationale;

— context and sensitivity of the object to be evaluated (for example presence of polychrome and gilt

surfaces);

— condition of the substrate, which may result in greater risk of harm during testing;

— form of the substrate (flat or carved surface).

These factors may exclude the use of one or more cleaning methods, which would be unsuitable.

This document takes into account the extreme variability of both the constituent materials and the

conditions of the object, prescribing a procedure of analytical tests and comparing the extent of possible

damage, which may result from each cleaning method tested.

“Harmfulness” indicates the level of risk of the variety of unwanted changes, which may appear not only

in short-term but also in long-term after cleaning.

This may include the deterioration of the substrate, the change of porosity or surface roughness, the

release of residual substances and formation of stains, which are not compatible with the material and or

which could interfere with future conservation intervention.

The potential harmfulness of a cleaning method may be greater when it is applied to a deteriorated

material.

Evaluation of effectiveness and potential harmfulness of cleaning methods need to be carried out on site

by establishing a “trial area” as a preliminary step before any extensive work is started.

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SIST EN 17488:2021
EN 17488:2021 (E)

The process of cleaning requires careful evaluation throughout the work. This is initiated at the primary

evaluation through the execution of trials and continues with the monitoring and optimization during the

selected process. Trials aim to identify the method(s) of cleaning which produce an acceptable result at

minimum risk to the object. Even an extensive sampling procedure may fail to identify all the conditions

which exist on a cultural object therefore ongoing evaluation of the cleaning and the effects on the

substrate are vital. If necessary, cleaning needs to be halted to re-appraise the methods used or to

undertake further testing where areas of increased sensitivity or uncertainty are uncovered. This

document identifies the means by which cleaning methods may be selected and evaluated as part of

conservation interventions.

Unwanted interactions may arise from different substrate and cleaning method combinations. Some

features of a given substrate may cause it to be particularly damaged depending on the method and

circumstances of its use. These specific combinations will increase likelihood of damage. In some

circumstances the synergistic effects can be easily predicted, e.g. a salt-laden wall masonry may be

seriously affected by a water-based method, even if we know that generally this cleaning method is gentle

and of low aggressiveness. The assessment of the synergistic effects should take into consideration that

damage may emerge after some considerable elapsed time.

The initial assessment for a building or similar immovable object will take place on site with non-invasive

systems. If necessary, it may be followed by appropriate micro-invasive or invasive laboratory analysis

(Figure 1, Table 1).

As there are many different cleaning methods and the results can vary greatly it is necessary to carefully

evaluate any proposed technique/system before trial and subsequent application. Reference to standard

EN 17138 is required to undertake this.

Cleaning methods considered in EN 17138 were divided into four categories: Water cleaning, mechanical

cleaning, physical cleaning and chemical cleaning. Each method requires different considerations in order

to select the most appropriate investigations.

Assessment of harmfulness for chemical cleaning methods needs additional investigation with respect to

the possible interactions between the chemicals and the products to be removed, notably the formation

of by-products which could be harmful for the substrate. As a consequence, the procedure for chemical

cleaning will follow a different pathway (Figures 2 and 6, Table 1).
The document is composed of two parts:

a) General procedure (Part A) to be applied when the evaluation of the effects of cleaning of a cultural

heritage object surface is needed.

b) Analytical procedure (Part B) for testing cleaning methods under development on specimens of

analogous material similarly decayed.

Cleaning methods and materials, which are under development should not be evaluated on cultural

heritage objects surface but they should be tested according to the analytical procedure described in

part B.
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SIST EN 17488:2021
EN 17488:2021 (E)
1 Scope

This document gives the test methodology for evaluation of both harmfulness and effectiveness of a

cleaning method as applied to porous inorganic materials. Mural paintings and polychromy are excluded.

Evaluation includes the use of on-site analyses and/or laboratory studies.

The evaluation of the potential harm has a higher priority than the effectiveness in order to prevent

overcleaning. It is important that cleaning is always at the minimum level deemed effective and that it

respects the original surface and finishes. Overcleaning is a term used to indicate that irreversible damage

has been done by the unnecessary removal of materials, which are part of the value of the object.

This document applies to:

a) Part A: all methods of cleaning, which have characteristics of parameterization and reproducibility

(see EN 17138).
b) Part B: all new methods that are under development.

This document applies to evaluate the optimum methods for cleaning and the optimization of the

parameters of the selected cleaning process.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

EN 15801, Conservation of cultural property - Test methods - Determination of water absorption by

capillarity

EN 15886, Conservation of cultural property - Test methods - Colour measurement of surfaces

EN 16095, Conservation of cultural property - Condition recording for movable cultural heritage

EN 16096, Conservation of cultural property - Condition survey and report of built cultural heritage

EN 16302, Conservation of cultural heritage - Test methods - Measurement of water absorption by pipe

method

EN 16455, Conservation of cultural heritage - Extraction and determination of soluble salts in natural stone

and related materials used in and from cultural heritage

EN 16515:2015, Conservation of Cultural Heritage - Guidelines to characterize natural stone used in

cultural heritage

EN 17138:2018, Conservation of Cultural Heritage - Methods and materials for cleaning porous inorganic

materials
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SIST EN 17488:2021
EN 17488:2021 (E)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— IEC Electropedia: available at https://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
3.1
cleaning effectiveness
ability to remove unwanted material
3.2
harmfulness

any undesired change in the substrate to be cleaned, except the removal of the unwanted material

3.3
invasive analysis

requires the removal of powder or of a fragment from the surface or from the bulk of the object

3.4
micro-invasive analysis
no visible damage on the surface
Note 1 to entry: A small amount of material is collected (1 mg or less).
3.5
non-invasive analysis

contact between object surface and apparatus used for measurements is avoided; no material is removed

from the object
3.6
sample

portion of material, ideally representative, removed from the cultural property for scientific investigation

[SOURCE: EN 16085:2012, 3.2]
3.7
specimen
part considered representative of the material constituting an object
Note 1 to entry: The specimen can have different origins and can be taken from:

— materials similar to those constituting the object under study (e.g. stone quarries);

— reference materials, for instance, specifically prepared comparative materials;

— available materials from the object.

Note 2 to entry: The number and dimension of the specimens can be different depending on difficulties

encountered in sampling the required amount of material.
[SOURCE: EN 15886:2010, 3.11]
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SIST EN 17488:2021
EN 17488:2021 (E)
3.8
trial area
location where the cleaning method under evaluation is tested
3.9
unwanted material
substances to be removed indicated by the conservation plan
4 Abbrevations
The following list of analytical techniques is considered:
4.1 UVF: Fluorescence induced by Ultraviolet Radiation
4.2 pXRF: Portable X Ray Fluorescence
4.3 TLOM: Transmitted Light Optical Microscopy
4.4 RLOM: Reflected Light Optical Microscopy
4.5 UVOM: Ultraviolet Optical Microscopy

4.6 ESEM/SEM: Environmental Scanning Electron Microscopy/Scanning Electron Microscopy

4.7 WDS: Wavelength Dispersive Spectroscopy
4.8 EDS: Energy Dispersive Spectroscopy
4.9 FTIR: Fourier Transform Infrared Spectroscopy
4.10 Raman: Raman Spectroscopy
4.11 IC: Ion Chromatography
4.12 pH-m: pH measurement
4.13 WDT: Water Drop Test
5 General procedure (Part A)
5.1 Overview

Before starting to evaluate cleaning methods, a condition survey and a condition report are needed in

accordance with standards EN 16095 and EN 16096.

The initial assessment for a building or similar immovable object should take place on site with non-

invasive systems. Successively, if necessary, it may be followed by appropriate micro-invasive or invasive

laboratory analysis (Figure 1, Table 1).

To facilitate the analytical evaluation of cleaning methods in each individual case the following systematic

procedure is proposed. It consists of a number of consecutive stages as described in the flow chart of

Figure 1. Due to the wide variability of each individual case, the whole sequence proposed shall be case

specific and is up to the responsibility of the professional in charge.

Evaluation procedures depend also on time available and resources (budget and staff). In all cases, the

outcome should be the best possible one for the object.
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SIST EN 17488:2021
EN 17488:2021 (E)
Figure 1 — Flow chart of the procedure for cleaning evaluation
5.2 Identification of substrate and characterization of unwanted materials

The chemical, mineralogical and the micro-structural characteristics of the material constituting the

object shall be known or preliminarily identified (EN 16515) as well as the extent, nature and thickness

of the unwanted materials to be removed.

The layer of unwanted materials and the altered surface of substrate shall be distinguished from each

other at the investigation stage, so that the required degree of cleaning can be determined (see

EN 17138:2018, 5.2).

The preliminary investigations using non-invasive systems should be carried out on a defined trial area

selected as representative of the main surface material composition and cleaning problem.

The main non-invasive systems to be considered are:
a) portable microscope for optical observations;
b) portable XRF equipment for the identification of chemical elements;

c) portable fluorescence induced by UV radiation equipment for the identification of fluorescent

compounds;
d) portable FTIR spectrometer especially in the presence of organic materials.

For laboratory investigations the procedure reported in EN 16515 (examination of specimens under

stereo-microscope, petrographic examination, mineralogical analysis by X-ray diffraction XRD,

examination by SEM/ESEM, chemical analysis) shall be performed.

The identification of organic components, not considered in EN 16515, shall be performed by FTIR

spectroscopy and when necessary by GC-MS (gas chromatography and mass spectrometry).

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SIST EN 17488:2021
EN 17488:2021 (E)
5.3 Selection of suitable cleaning methods to be tested

As some cleaning methods are inappropriate where painted finishes are present, their presence or

absence shall be established before any evaluation is started.

After the identification of the substrate and of the composition of unwanted materials a selection of

suitable cleaning methods, according to the results obtained, is carried out on the “trial area”.

For the application of this document the following cleaning method categories are considered (see

EN 17138):

a) water cleaning (restricted to the following: nebulous spray or intermittent mist spray, water spray

at low pressure, steam cleaning, aqueous poultices or packs with absorbent material);

b) mechanical
...

SLOVENSKI STANDARD
oSIST prEN 17488:2020
01-september-2020

Ohranjanje kulturne dediščine - Postopek za analitično vrednotenje in izbiro metod

za čiščenje poroznih anorganskih materialov, uporabljenih pri tej kulturni dediščini

Conservation of cultural heritage - Procedure for the analytical evaluation and selection

of cleaning methods for porous inorganic materials used in cultural heritage
Erhaltung des kulturellen Erbes - Methodologie für die Bewertung von

Reinigungsmethoden - Verfahren für die analytische Prüfung der Objekte des kulturellen

Erbes

Conservation du patrimoine culturel - Procédure pour l'évaluation analytique et le choix

des méthodes de nettoyage des matériaux inorganiques poreux dans les bâtiments
d'intérêt patrimonial
Ta slovenski standard je istoveten z: prEN 17488
ICS:
97.195 Umetniški in obrtniški izdelki. Items of art and handicrafts.
Kulturne dobrine in kulturna Cultural property and
dediščina heritage
oSIST prEN 17488:2020 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN 17488:2020
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oSIST prEN 17488:2020
DRAFT
EUROPEAN STANDARD
prEN 17488
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2020
ICS 97.195
English Version
Conservation of cultural heritage - Procedure for the
analytical evaluation and selection of cleaning methods for
porous inorganic materials used in cultural heritage

Conservation du patrimoine culturel - Procédure pour Erhaltung des kulturellen Erbes - Methodologie für die

l'évaluation analytique et le choix des méthodes de Bewertung von Reinigungsmethoden - Verfahren für

nettoyage des matériaux inorganiques poreux dans les die analytische Prüfung der Objekte des kulturellen

bâtiments d'intérêt patrimonial Erbes

This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee

CEN/TC 346.

If this draft becomes a European Standard, 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.

This draft European Standard was established by CEN 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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,

Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are

aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without

notice and shall not be referred to as a European Standard.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 17488:2020 E

worldwide for CEN national Members.
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oSIST prEN 17488:2020
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Contents Page

European foreword .........................................................................................................................................................................4

Introduction.........................................................................................................................................................................................5

1 Scope ........................................................................................................................................................................................7

2 Normative references ....................................................................................................................................................7

3 Terms and definitions....................................................................................................................................................7

4 Abbreviations .....................................................................................................................................................................8

5 General procedure (Part A) ........................................................................................................................................9

5.1 Overview of the procedure .........................................................................................................................................9

5.2 Identification of substrate and characterization of unwanted materials .......................................9

5.3 Selection of suitable cleaning methods to be tested .................................................................................10

5.4 Localization, delimitation and numbering of the cleaning trial areas ...........................................10

5.5 Design of the evaluation procedure....................................................................................................................11

6 On site surface investigations ................................................................................................................................13

6.1 Optical observation ......................................................................................................................................................13

6.1.1 Portable digital microscope ....................................................................................................................................13

6.1.2 Raking light .......................................................................................................................................................................13

6.1.3 Portable digital stereo microscope .....................................................................................................................14

6.1.4 Fluorescence induced by UV radiation .............................................................................................................14

6.2 Chemical/physical analysis .....................................................................................................................................14

6.2.1 Measurement of colour ..............................................................................................................................................14

6.2.2 Elemental analysis by portable XRF ...................................................................................................................15

6.2.3 Molecular analysis by portable FTIR .................................................................................................................15

6.2.4 Surface ion analysis......................................................................................................................................................15

6.3 Water absorption assessment................................................................................................................................15

6.3.1 Determination of water absorption by pipe method................................................................................15

6.3.2 Determination of water absorption by contact sponge method ........................................................16

6.3.3 Water drop test ...............................................................................................................................................................16

7 Laboratory analysis on samples taken from trial areas .........................................................................16

7.1 General.................................................................................................................................................................................16

7.2 Sampling .............................................................................................................................................................................16

7.3 Chemical/physical analysis .....................................................................................................................................17

7.3.1 Examinations of fragments surfaces by RLOM, SEM-ESEM and EDS microanalysis ...............17

7.3.2 Examinations of thin and polished and cross section by RLOM, SEM-ESEM and EDS

microanalysis...................................................................................................................................................................18

7.3.3 Vibrational spectroscopy (FTIR, micro-FTIR and Raman)....................................................................18

7.4 Surface morphology analysis..................................................................................................................................18

7.4.1 Measurement of roughness (see ISO 25178).................................................................................................18

7.5 Wet chemical analysis (on aqueous extract) in the case of chemical cleaning .........................19

7.5.1 Extraction procedure ..................................................................................................................................................19

7.5.2 Analysis on aqueous extract....................................................................................................................................21

8 Overall evaluation of results obtained..............................................................................................................21

9 Analytical procedure for testing methods under development on specimens of

analogous material (Part B) ....................................................................................................................................22

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9.1 General procedure ........................................................................................................................................................22

9.2 Preparation of test specimens ...............................................................................................................................25

9.2.1 Number and dimensions of test specimens ...................................................................................................25

9.2.2 Pre-conditioning of test specimens ....................................................................................................................25

9.3 Evaluation process of the cleaning method(s) under test .....................................................................25

9.4 Test analysis on specimens before and after the application of cleaning methods ...............25

9.4.1 General.................................................................................................................................................................................25

9.4.2 Determination of water absorption by capillarity.....................................................................................26

9.4.3 Colour measurement of surfaces..........................................................................................................................26

9.4.4 Observation of the surfaces by the stereo microscope............................................................................26

9.4.5 Determination of mass variation .........................................................................................................................26

9.4.6 Thin and polished cross sections analysis by RLOM, SEM-ESEM/EDS ............................................27

9.4.7 Thin and polished cross sections analysis by RLOM, SEM-ESEM/EDS on fragments of

surfaces................................................................................................................................................................................27

9.4.8 Analysis of aqueous extract for chemical cleaning ....................................................................................28

9.5 Cleaning application ....................................................................................................................................................28

9.6 Test report .........................................................................................................................................................................28

9.6.1 General information ....................................................................................................................................................28

9.6.2 Results of measurements on specimens ..........................................................................................................28

Annex A (normative) Examples of trial applications ................................................................................................31

Annex B (informative) Test carried out, findings, inference ................................................................................36

Annex C (informative) Specifications to be reported for different cleaning methods (see

EN 17138:2018)..............................................................................................................................................................46

C.1 Water cleaning ................................................................................................................................................................46

C.1.1 Nebulous spray and water spray ..........................................................................................................................46

C.1.2 Aqueous poultices with absorbent material .................................................................................................46

C.1.3 Steam cleaning ................................................................................................................................................................46

C.2 Mechanical cleaning.....................................................................................................................................................47

C.2.1 Micro blasting ..................................................................................................................................................................47

C.2.2 Wet jet micro blasting .................................................................................................................................................47

C.2.3 Cryogenic cleaning ........................................................................................................................................................47

C.3 Physical cleaning............................................................................................................................................................48

C.4 Chemical cleaning..........................................................................................................................................................48

C.4.1 Organic solvents .............................................................................................................................................................48

C.4.2 Acidic or alkaline solutions, chelating agents, surfactants ...................................................................48

C.4.3 Ion exchange resins......................................................................................................................................................49

Bibliography .....................................................................................................................................................................................50

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European foreword

This document (prEN 17488:2020) has been prepared by Technical Committee CEN/TC 346

“Conservation of Cultural Heritage”, the secretariat of which is held by UNI.
This document is currently submitted to the CEN Enquiry.
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Introduction

Cleaning is a conservation treatment aimed at the removal of material of natural or artificial origin, which

has the potential to damage the substrate, or which may limit the correct interpretation of the object or

parts thereof.

The actions required for cleaning involve a degree of risk for the object and therefore demand extreme

caution. Cleaning needs to be effective while not being harmful to the object.

Cleaning operation needs to take into account the compatibility definition (EN 15898) as the “extent to

which one material can be used with another material without putting significance or stability at risk”.

Extending the definition of compatibility to the cleaning action a “compatibility analysis” should therefore

ascertain how cleaning actions (in terms of effectiveness and harmfulness) would impact on the

significance and stability of the heritage object.

A successful cleaning strategy requires the careful consideration of a number of aspects which include

but are not limited to the following:

— context and sensitivity of the object to be evaluated (for example presence of polychrome and gilt

surfaces);

— conservation condition of the substrate, which may result in greater risk of harm during testing;

— the aim of the cleaning in terms of which materials are to be removed and which to be retained;

— function and form of the substrate (flat or carved surface).

These factors may exclude the use of one or more cleaning methods, which would be unsuitable.

This document takes into account the extreme variability of both the constituent materials and the

conditions of the object, prescribing a procedure of analytical tests and comparing the extent of possible

damage, which may result from each cleaning method tested.

“Harmfulness” indicates the level of risk of the variety of unwanted changes, which may appear not only

in short-term but also in long term after cleaning.

This may include the deterioration of the substrate, the increase of porosity or surface roughness, the

release of residual substances and formation of stains, which are not compatible with the material and or

which could interfere with future conservation intervention.

The potential harmfulness of a cleaning method may be greater when it is applied to a deteriorated

material.

Evaluation of effectiveness and potential harmfulness of cleaning methods need to be carried out on site

by establishing a “trial area” as a preliminary step before any extensive work is started.

The process of cleaning requires careful evaluation throughout the work. This is initiated at the primary

evaluation through the execution of trials and continues with the monitoring and optimization during the

selected process. Trials aim to identify the method(s) of cleaning which produce an acceptable result at

minimum risk to the object. Even an extensive sampling procedure may fail to identify all the conditions

which exist on a cultural object and ongoing evaluation of the cleaning and the effects on the substrate

are therefore vital. If necessary, cleaning needs to be halted to re-appraise the methods used or to require

further testing where areas of increased sensitivity or uncertainty are uncovered. This document

identifies the means by which cleaning methods may be selected and evaluated as part of conservation

interventions.

Unwanted interactions may arise from different substrate and cleaning method combinations. Some

features of a given substrate may cause it to be particularly damaged depending on the method and

circumstances of its use. These specific combinations will increase likelihood of damage. In some

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circumstances the synergistic effects can be easily predicted, e.g. a salt-laden wall masonry may be

seriously affected by a water-based method, even if we know that generally this cleaning method is gentle

and of low aggressiveness. The assessment of the synergistic effects should bear in mind that damage

may emerge after some considerable elapsed time.

The initial assessment for a building or similar immovable object will take place on site with non-invasive

systems. If necessary, it may be followed by appropriate micro-invasive or invasive laboratory analysis

(Figure 1, Table 1).

Cleaning methods considered in EN 17138:2018 were divided into four categories: Water cleaning,

mechanical cleaning, physical cleaning and chemical cleaning. Each method requires different

considerations in order to select the most appropriate investigations.

Assessment of harmfulness for chemical cleaning methods needs additional investigations with respect

to the possible interactions between the chemicals and the products to be removed, notably the formation

of by-products which could be harmful for the substrate. As a consequence, the procedure for chemical

cleaning will follow a different pathway (Figures 2 and 6, Table 1).

Evaluation tests of methods or materials which are under development should not be undertaken on

objects of cultural heritage. The methods outlined in this document are instead to be used on analogous

materials, similarly decayed, with enough material employed to fully evaluate pre and post cleaned

conditions. In the case of testing for new cleaning methods, therefore, follow the procedure in Part B.

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1 Scope

This document gives the test methodology for evaluation of both harmfulness and effectiveness of a

cleaning method as applied to porous inorganic materials. These include materials such as natural or

artificial stone, included those with painting layers as finishes. Evaluation admits the use of on site

instrumental analyses and the taking of samples to be studied in laboratory.
Harmfulness evaluation has a priority over the effectiveness.
This document applies to:

a) all methods of cleaning, which have characteristics of parameterization and reproducibility (see

EN 17138:2018). Part A;
b) all new methods that are under development. Part B.

This document applies to evaluate the optimum methods for cleaning and the optimization of the

parameters of the selected cleaning process.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

EN 15801, Conservation of cultural property — Test methods — Determination of water absorption by

capillarity

EN 15886, Conservation of cultural property — Test methods — Colour measurement of surfaces

EN 16302, Conservation of cultural heritage — Test methods — Measurement of water absorption by pipe

method

EN 16515:2015, Conservation of Cultural Heritage — Guidelines to characterize natural stone used in

cultural heritage

EN 17138:2018, Conservation of Cultural Heritage — Methods and materials for cleaning porous inorganic

materials
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp

With reference to the integrity of the object surface, the nature of the analysis and the diagnosis may be

described as one of the following:
3.1
non-invasive

contact between object surface and apparatus used for measurements is avoided. No material is removed

from the object
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3.2
micro-invasive
no visible damage on the surface
Note 1 to entry: A small amount of material is collected (1 mg or less).
3.3
invasive

consists of the removal of powder or of a fragment from the surface or from the bulk of the object

With regard to the sampled material, the analysis could be:
3.4
not destructive
samples could be re-used for several analytical purposes

Note 1 to entry: Samples scarcely modified (i.e. cross sections, spot test, ESEM sputtered samples) are also

included in this category.
3.5
destructive
sampled material is modified (burned, solubilized, reacted, etc.)
3.6
effectiveness
ability in the removal of the unwanted material
3.7
harmfulness

any undesired change in the substrate to be cleaned, except the removal of the unwanted material

3.8
trial areas
set of areas where testing the planned cleaning method
3.9
unwanted material

material to be removed indicated by the restoration design because of legibility or conservation reasons

4 Abbreviations
The following list of analytical techniques is considered:
4.1 UVF: Fluorescence induced by Ultraviolet Radiation
4.2 pXRF: Portable X Ray Fluorescence
4.3 RLOM: Reflected light Optical Microscopy
4.4 UVOM: Ultraviolet Optical Microscopy

4.5 ESEM-EDS/WDS: Environmental Scanning Electron Microscopy with Energy or Wavelength

Dispersive Spectroscopy
4.6 FTIR: Fourier Transmission Infrared Spectroscopy
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4.7 Raman: Raman Spectroscopy
4.8 IC: Ionic conductivity
4.9 pH-m: pH measurement
4.10 WDT: Water drop test
5 General procedure (Part A)
5.1 Overview of the procedure

To facilitate the analytical evaluation of cleaning methods in each individual case the following systematic

procedure is proposed. It consists of a number of consecutive stages as described in the flow chart of

Figure 1. Due to the wide variability of each individual case the whole sequence proposed shall be

adapted time by time and is up to the responsibility of the professional in charged.

Figure 1 — Flow chart of the procedure for cleaning evaluation
5.2 Identification of substrate and characterization of unwanted materials

The chemical, mineralogical and the structural characteristics of the material constituting the object shall

be preliminarily identified (EN 16515:2015) as well as the extent, nature and thickness of the unwanted

materials to be removed.
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The layer of unwanted materials and the altered surface of substrate shall be distinguished from each

other at the investigation stage, so that the level of cleaning can be selected (see EN 17138:2018, 5.2).

The investigation should commence with the use of non-invasive systems, followed by appropriate

laboratory investigations, micro-invasive or invasive, when and if required.

The preliminary investigations using non-invasive systems should be carried out on a defined test area

selected as representative of the main surface material composition and cleaning problem.

The non-invasive systems considered are:
a) portable microscope for optical observations;
b) portable XRF equipment for the identification of chemical elements;

c) portable fluorescence induced by UV radiation equipment for the identification of fluorescent

compounds. In the presence of organic materials, identified by UV fluorescence, a portable FTIR

spectrometer should be used.

For laboratory investigations the procedure reported in EN 16515:2015 (Examination of specimens

under stereo-microscope, petrographic examination, mineralogical analysis by X-ray diffraction XRD,

examination by ESEM, chemical analysis) shall be performed.

The identification of organic components, not considered in EN 16515:2015, shall be performed by FTIR

spectroscopy and when necessary by GC-MS (gas chromatography and mass spectrometry).

5.3 Selection of suitable cleaning methods to be tested

After the identification of the substrate and of the composition of unwanted materials a selection of

suitable cleaning methods, according to the results obtained, is carried out on the “trial area”.

For the application of this document the following cleaning methods are considered (see

EN 17138:2018):

a) water cleaning (restricted to the following: nebulous spray or intermittent mist spray, water spray

at low pressure, steam cleaning, aqueous poultices or packs with absorbent material);

b) mechanical cleaning (restricted to the following: micro blasting, wet jet micro blasting, cryogenic

cleaning);

c) chemical cleaning (application of organic solvents, application of acidic or alkaline solutions,

application of chelating agents, application of surfactants, gel cleaning, application of ion exchange

resins);
d) physical cleaning (laser cleaning).
...

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