Metals conservation research newsletter

[Alison Wain <alison@charvolant.org>]

David Hallam has sent in a copy of a metals  conservation research
newsletter called BROMEC 3 being put together by Christian Degrigny. If
anyone is interested in being placed on the mailing list for this they
can contact David or Christian directly. I have put a copy of the latest
edition in text format in this message for you to be able to see whether
it might interest you. The original is nicely formatted and much easier
to read but I wasn't confident of it being readable by the time it got
through to the mailing list. If anyone wants a copy of the original
please let me know.

Alison

BROMEC 3

Bulletin of the Research On MEtal
Conservation
August 2002
Editor: Christian Degrigny

Tel: +358 9 511 9406
Fax:+358 9 823 5791
christian.degrigny@iad.evtek.fi


Metal working group


Editorial

Summer time is usually a very quiet time. Permanent staff is on vacation
but students are on
internship. Most of the research projects presented in this issue have
been partly conducted by
students in different institutions and conservation laboratories.

For this third issue we got new contributions from Greece and France.
You will find too some
preliminary conclusions of research projects conducted in Finland by
Finnish or foreign
students.

Jean-Bernard Memet, conservation scientist at Arc´Antique, Nantes and
Régis Bertholon,
senior lecturer at the University of Paris Sorbonne I (Master degree in
conservation of
Cultural Heritage) will represent France in the future. I am very happy
to welcome them
among the team of BROMEC correspondents.

Some colleagues from Eastern Europe were concerned that there was no
correspondent in
their own country. Contacts have been taken since. Let´s hope in the
near future to find
motivated colleagues ready to contribute to our bulletin.

A new section has been opened for those seeking for collaborations on
projects that they want
to set up (see calls for collaboration).

I spent some time recently to find interesting web-sites where research
in conservation of
metals is mentioned. As you certainly know a lot of important research
programmes are now
conducted on a European level (Fifth Framework Programme ? Key Action
"The City of
tomorrow and cultural heritage" and CULTURE 2000). For those interested
in programmes
funded by the European Commission, consult the following web-site:
http://europa.eu.int/comm/culture/finan_en.htm. CULTURE 2000 and Energy,
environment
and sustainable development programmes specific web-sites can be found
there. The key
action "City of tomorrow and Cultural heritage" can be found under the
latter.

The next important event for all of us is the forthcoming ICOM-CC
triennial conference in
Rio de Janeiro in September 2002. William Mourey is leaving his position
as co-ordinator of
the ICOM-CC Metal Group and we wish him good luck in his future projects
in South-Africa
where he will represent CNRS. In Rio the new co-ordinator will be
elected. Since I am
planning to go there, I will take this opportunity to advertise our new
bulletin.

I hope that you will again enjoy the reading of this new issue of the
bulletin.

The Editor
Christian DEGRIGNY
Principal lecturer, Conservation Department
EVTEK Institute of Art and Design
Lummetie 2, 01300 Vantaa - FINLAND



Contents:


Applied research projects

  In-situ conservation of grey cast iron cannon

  Iron / waterlogged wood artefacts : microbiological and
electrochemical study

  The removal of bronze spray paint from a collection of Outdoor
bronze
           monuments in a suburb of Athens


Ongoing research projects


  The conservation of historical Greek Porpi (Belt buckles)

  Protecting historical iron knives from persistent rust spots

  Iron tin-plated finds

  Examination and stabilisation of a collection of lead medals from the
National
           Museum of Finland

  Electrolytic stabilisation of marine iron artefacts in neutral
solution


New research projects


  Archaeological lead artefacts : case study


Calls for collaboration


  The conservation of ethnographic metal collections from the Eastern
        Mediterranean area

  Development of a course on the use of electrolytic techniques in metal
conservation



Applied research projects


 In-situ conservation of grey cast iron cannon (MMF/ EVTEK Institute of
Art
and Design / EVTEK Institute of Technology)

During the 2002 summer season, the survey of the cannons on the Gustav
Adolf
wreck site was continued. The equipment needed to conduct in-situ
measurements
of Ecorr and pH has been set up too. Due to the bad weather and timing
problems
only a few cannons could be studied. Rami Kokko has chosen two cannons
partly
cleaned from their crust and two others apparently still well protected.
On the two
first cannons Ecorr measurements will be conducted directly on the
remaining
metal surface (covered with thick graphitic corrosion layer - GCL). On
the two
others the same measurements will require the drilling of the crust (and
the GCL
too). pH measurements are planned too in this latter case. Different
values of Ecorr
are expected from the four cannons depending on the nature of the
material
surface. New measurements should be taken once a year in the future to
determine
whether the cannons have or not reached a stable state or are still
actively
corroding.

The use of sacrificial anodes to protect the cannons (cathodic
protection) will be
tested on one cannon to have an idea on how effective it can be.
Commercial zinc
anodes will be used and a new frame has been constructed to improve the
attachment of the anodes to the cannon.

In parallel Tiina Andersson, student at the EVTEK Institute of
Technology has
conducted a laboratory study on the conditions of formation of the
preliminary
oxide-sediment layer on accidentally cleaned grey cast iron when
protected with
sacrificial anodes. Baltic sea, zinc anodes and modern cast iron samples
are
considered for these experiments.

The influence of the sample surface and the size of the anodes on the
formation of
the protective layer have been studied.


Further research: In Autumn we will concentrate on the following points:
1/
simulation of the immersion of grey cast iron samples (with different
surface
preparations) in artificial Baltic sea water to plot Ecorr values versus
time. The
objective is to compare Ecorr values measured on site to those obtained
in the
laboratory. 2/ determination of a protocol for the good protection of
grey cast iron
using sacrificial anodes.



Contacts: Christian Degrigny (EVTEK Institute of Art and Design), Rami
Kokko
(Maritime Museum of Finland) & Tiina Andersson (EVTEK Institute of
Technology)
Funding: Finnish Cultural Foundation, MMF and EVTEK Institute of
Technology


Applied research projects


  Iron / waterlogged wood artefacts : microbiological and
electrochemical study
(Arc'Antique / ARC-Nucléart / CRCDG),

The discovery, in 1995, of 29 marine iron / wood composite rifles of the
17th century
led the French conservation laboratories Arc'Antique and ARC-Nucleart to
develop a
new research programme on the treatment of such artefacts. The approach,
based on
the concomitant use of a corrosion inhibitor and polyethylene glycol
(PEG), gave
excellent results as far as the iron protection and the wood
consolidation are
concerned.

The chosen inhibitor, Hostacor IT® is a triethanolamine associated with
a carboxylic acid. Preliminary
studies have consecrated this corrosion inhibitor as very effective on
freshly sandblasted iron or steel
[1, 2]. Thus, a new protocol was adopted for the conservation and
restoration of this collection [3]. But
during the storage and PEG impregnation, we have noticed the apparition,
at the objects surface, of an
important microbial and fungi contamination.

That is one of the reasons which led Arc'Antique and ARC-Nucléart to
associate with
the CRCDG in a three years research programme which began in October,
2001. The
aim of this research programme is to assess the influence of the living
species on both
the electrochemical properties of the storage solutions and the chemical
evolution of
the corrosion products, with a focus on sulphur based corrosion
products.

This first year consists in a two-stage research which begins, on one
hand, with the
description and counting of all this biomass and, on the other hand,
with the selection
in this total biomass of some representative micro-organisms, such as
bacteria, fungi
and yeast on which we will test some new biocides.

In addition, a MsS scientist, Mylène Lardoux, studies during 6 months
the electrochemical and
chemical interactions between the iron inhibitor and pre-corroded iron
and steel surfaces.


[1] : Guilminot, E, PhD report, Ecole Nationale Polytechnique de
Grenoble, France, october 2000.
[2] : Argyropoulos, V., Rameau, J-J., Dalard, F. and Degrigny, C.,
Studies in Conservation, 44 (1999)
49-57
[3] : Degrigny, C. and Guilminot, E., Cahier Technique ARAAFU 5 (1998)
5-10


Contacts: Nathalie Huet & Jean-Bernard Memet (Arc'Antique), Quoc Khoï
Tran
(ARC-Nucléart) & Malalanirina Rakotonirainy (CRDCG)
Funding: MRT



Applied research projects


  The removal of bronze spray paint from a collection of Outdoor bronze
monuments in a suburb of Athens (TEI)

Around 5 years ago, the then mayor of Nea Smyrni decided that he would
undertake
the treatment of the Outdoor bronze monuments of his city, by hiring two
workers to
spray paint on each monument to give them a uniform bronze colour.  The
result upset
the relatives of the deceased artist who has made the majority of the
bronze
monuments.

The project needs to determine the best method to remove the bronze
spray paint
without damaging the original surface underneath.  In some instances,
especially for
smaller objects solvents will be used.  However, for large monuments,
solvents are
not practical since they are toxic, and mechanical methods will have to
be considered.
The research proposes to determine the best method to apply for the
removal of the
spray paint.


Contact: Vasilike Argyropoulos (TEI of Athens)
Funding: Municipality of Nea Smyrni



Ongoing research projects


  The Conservation of historical Greek Porpi (Belt buckles) (TEI)

Greek costume belt buckles from the 16th century to modern day are
investigated in
terms of their historical significance, styles, and technological
make-up.  Most Porpi
made for Greek costumes are made of silver alloys and nickel silver.
The
conservation problems in terms of corrosion and treatment are
considered.
Ethnographic collections throughout Greece will be considered.

Contact: Vasilike Argyropoulos (TEI of Athens)
Funding: no external funding


Ongoing research projects


  Protecting historical iron knives from persistent rust spots (TEI,
CMA)

A collection of around 400 historic 19th and 20th century iron knives
housed at the
Criminal museum in Athens (CMA), Greece have been treated by the
students from
the Dept. of Conservation of Antiquities & Works of Art, T.E.I. of
Athens.  The
knives are coated (with Paraloid B72 followed by Renaissance wax) for
added
protection, since the conditions of the museum are not controlled.
However, after as
little as 2 weeks around 30% of the knives show signs of active rust
spots.  The
research proposes to find a suitable corrosion inhibitor to apply
underneath the
coating to help to minimise the corrosion problems encountered during
the exhibition
of the collection.


Contact: Vasilike Argyropoulos (TEI of Athens)
Funding: no external funding


Ongoing research projects


  Iron tin-plated finds (Arc'Antique).

The aim of this project is to detect and preserve, within the corrosion
products, tin-
plates on archaeological iron-based artefacts. Many pieces of the
Carolingian Period
(9th-10th century to the end of the Middle Ages) examined with X-raying
method are
showing a particular distinctive out-lining (high density to the X-rays)
in relation with
their original tin-plating (or other covering metals?). That is
particularly the case for
small fittings and cavalry equipment.

First of all, during the conservation work, there is no external visual
evidence of this
finishing treatment (aesthetic and protective) because of the presence
of iron
corrosion products on and under the tin-plate (excepting the related
cases of iron finds
from the York Viking period which were less corroded).

Secondly, in some cases, we have noticed with the X-rays the
disappearance of this
tin-plate layer during the stabilisation treatments and particularly
during the
dechlorination involving an alkaline sulphite solution (Na2SO3 + NaOH).

This new research programme involves MsS students and is based on 3
major axes:
- The comprehension of the chemical dissolution of tin-plate in alkaline

solutions,
- The detection of this layer in the attempt to get the original surface
during the
mechanical removal of external corrosion products.
- The development of a simple qualitative chemical test to identify tin
in
external corrosion products of iron.


Coordination: Stéphane Lemoine & Manuel Leroux (Arc'Antique)
Funding: no external funding



Ongoing research projects


  Examination and stabilisation of a collection of lead medals from the
National
Museum of Finland (EVTEK Institute of Art and Design / HEAA, filière
HES-
CRAE / NMF)

The initial objective of this project conducted by Martin Ledergerber,
Swiss conservation
student from HEAA, HES-CRAE Department, was to define a protocol to
remove organic
coatings present originally on lead medals and to preserve at the same
time the corrosion layer
underneath with surface information. This cleaning process should be
followed then by a
stabilisation treatment. Because of the powdery and loosely adherent
corrosion products
treatments involving mechanical contact with the surface should be
minimal. Only the
immersion in solvents has been evaluated during this first step.

As mentioned before the collection of the Numismatic Department of the
National Museum
of Finland was considered for this project. This collection has suffered
recently from an
exposure to high relative humidity (to 60%) and higher temperatures than
usual. Due to the
storage in wooden cabinets, corrosion problems occurred. A modified Oddy
test (with lead
coupons only) has been performed on most of the materials which are
present in the storage
area and most of them appeared to give negative results. Further
analysis of the different
corrosion products formed during the test are planned in the future. It
would be quite
interesting to determine which corrosion products are aggressive
resulting then from an active
corrosion and which ones are stable.

A preliminary survey of the collection has revealed that most of the
medals are free of any
protection. Only one artefact had been covered with an organic coating
which has been
identified by FTIR as a PVAC (poly-vinyl acetate) compound. These
compounds were used
indeed some years ago by the NMF. They may have favoured the corrosion
processes.

During the project electrolytic measurements have been performed to
assess the efficiency of
the electrolytic stabilisation of artificially corroded lead coupons
with or without the presence
of organic protections. Different compounds were considered for the
protection: natural
resins, waxes, nitro-cellulose lacquers and acrylic copolymers. Similar
techniques were used
too to determine the optimal conditions of the cleaning process (time of
immersion in
solvents). Other approaches were tested as well such as the use of
pigmented resins but the
results were inconsistent and difficult to interpret.

At the end of this first part of the project, it appears that the
cleaning of ancient organic
coatings on lead artefacts is needed to ease and complete the
stabilisation treatment of active
lead artefacts. But the appropriate solvents have to be chosen. Optimal
conditions of cleaning
have to be given too. Martin is continuing his project in Switzerland
(exposure of samples to
solvents as vapours and use of atomic oxygen treatment). Further results
are expected by the
end of this year.


Contacts: Christian Degrigny (EVTEK Institute of Art and Design), Martin

Ledergerber (HEAA du Canton de Neuchatel, La Chaux-de-Fonds,
Switzerland) &
Pia Klaavu (NMF)
Funding: EVTEK Institute of Art and Design, NMF





Ongoing research projects


  Electrolytic stabilisation of marine iron artefacts in neutral
solution (EVTEK
Institute of Art and Design)

The objective of this work introduced in BROMEC 2 has been to extract
electrolytically chlorides from iron based marine artefacts associated
with other
materials. The use of a basic solution was impossible due to the nature
of these
materials: paint, rubber and glass. Instead a 1% (w/v) NaNO3 solution
was chosen.
The anode is a stainless steel grid.

The innovative part of this study was the complete monitoring of the pH
of the non-
buffered solution and both the cathodic and anodic potentials during the
cathodic
polarisation of the artefacts.

To define optimal parameters of polarisation, iron nails were first
considered to
simulate the behaviour of the iron part of the composite. General trends
were obtained
while modifying the cathodic (and anodic) potential to optimise the
chloride
extraction and the surface condition (polished and oxidised) of the
nails. One major
observation was that the pH was increasing quite fast as soon as the
cathodic potential
was decreasing under a certain value or the anodic potential was above
another
specific value. A different behaviour was observed when the nails were
slightly
oxidised. The increase of pH was not the general trend. Sometimes it was
decreasing.
But after some times the previous behaviour was observed. This
difference of trend
has been explained by the presence of the oxide layer. Our major concern
was the
behaviour of the whole system during the night where no control of the
different
parameters is possible. The stabilisation process lasts indeed several
days, week-ends
included. Thus this long term polarisation parameter has to be studied.

On archaeological artefacts the decrease of pH was on the contrary the
general trend.
Due to the presence of a thick GCL on the grey cast iron, it was
impossible to apply
such negative potentials as the ones obtained before. Polarisation was
conducted this
time using a constant anodic potential. Like before our objective was to
maintain a
constant pH for days and nights.

Chloride extraction was monitored and it appeared that by applying the
appropriate
potentials this extraction was effective.

Our future work will be to understand the change of pH during
polarisation and the
influence of the surface of the artefact considered. Electrochemical
reactions taking
place at the surface of the electrodes will be studied with a
potentiostat.

Contact: Christian Degrigny (EVTEK Institute of Art and Design) & Ilonne
de Groot
(ICN)
Funding: no external funding



New research projects


  Archaeological lead artefacts : case study (Arc'Antique)


For the last thirty years, numerous research programmes have been
developed to
study the corrosion of lead and its alloys (with Sn and Sb). The major
conservation
problems come from the stabilisation of the corroded surface which
contain the details
and all the historical descriptions of the artefacts (for medals and
seals for example).
Five years ago Arc'Antique developed a well controlled electrolytic
stabilisation
technique based on the consolidating reduction of lead. This technique
is now
successfully used on medals and seals stored in oak cabinets and damaged
by the
acetic acid vapours evolved. Unfortunately, we have recently reached
some limits of
this reduction treatment with the conservation and restoration
programmes of
archaeological lead artefacts.

First, it appears to be very difficult to determine on each artefact
whether the
corrosion is active or not under the white crust and corrosion products
(mainly lead
carbonate). Secondly when the electrolytic consolidating treatments are
applied, there
are always some areas on each artefact which cannot be reduced.

In the case of archaeological finds, the lead corrosion products are
mostly combined
with some minerals which form a diffusion barrier not only for the
reducing species
but also for the electrolyte.

The main features of this research programme are, on one hand, to
characterise the
chemical composition of the corrosion products by Raman Spectroscopy and

Scanning Electron Microscope coupled with Energy Dispersion
Spectrometer. On the
other hand, we are adapting the consolidating reducing treatment to
these
archaeological finds.


Contacts: Loretta Rossetti, Nathalie Huet & Jean-Bernard Memet
(Arc'Antique)
Funding: No external funding



Calls for collaboration



  The conservation of Ethnographic metal collections from the Eastern
Mediterranean area

Partners required: Museums with collections of metallic ethnographic
collections
from Eastern Mediterranean

Contact: Vasilike Argyropoulos (TEI of Athens)




Calls for collaboration



  Development of a course on the use of electrolytic techniques in metal

conservation

Objective: the conservation department of EVTEK Institute of Art and
Design has
developed in the past years a specific course on the use of electrolytic
techniques in
conservation. It is dedicated to students in conservation. General
concepts of metal
corrosion and definition of electrochemical and electrolytic parameters
are given but
the course concentrates mostly on the use of these parameters to monitor
the treatment
of simulated or original historical and archaeological artefacts

Our objective would be to involve more speakers, particularly from
abroad, to enlarge
the fields of application. Specific approaches could be proposed too
according to the
nature of the participants (students, trained conservators). The module
obtained could
then be used in other training schools for conservators.

Partners required: other training schools and lecturers interested in
giving lectures
in the field, experts (conservation and/or corrosion scientists)

Contact: Christian Degrigny



General information

Web-sites

Some sites offer interesting information on research applied to the
conservation field.
Specific studies on metals might be found.

- 5th Cultural Heritage Research: a Pan-European Challenge, Cracow
(16-19 May
2002).
The programme of the conference + list of posters can be found on:
www.heritage.ceti.pl.

- EC Advanced study course on "Science and technology of the environment
for
sustainable protection of cultural heritage
The programme and the course materials are available on:
www.ucl.ac.uk/sustainableheritage/learning/asc/index.html

- Laboratories on Science and Technology for the conservation of
European
Cultural Heritage
http://www.chm.unipg.it/chimgen/LabS-TECH.html

- Cost Action G8: Non destructive analysis and testing of museum objects

http://srs.dl.ac.uk/arch/cost-g8

- Cost Action G7: Artwork conservation by laser
http://alpha1.infim.ro/cost

- Protect our European Outdoor Bronze Monuments.
Provide a Good Practice Guide (GPG) for the protection of Outdoor bronze

monument: www.kae.gr/bronzemonuments/home.htm. Note that the GPG from
the web-site
is incomplete. Complete versions can be provided by the editor.

- Corrosion source. All kind of basic data needed when you study
corrosion problems
on metals can be found on that site.
www.corrosionsource.com

Future seminars and conferences


- ICC 2002 - 15th International Corrosion Congress (22-27 September
2002, Granada,
Spain). For more information consult http://www.15icc2002.com/intr.html

- ICOM-CC Triennial Meeting (23-27 September 2002, Rio de Janeiro,
Brazil). For
more information consult www.icom-cc.org/rio2002

- Introduction course on the use of lasers in art conservation (4-6
September and
20-22 November 2002, Art Innovation, Hengelo, The Netherlands). For more

information contact Art Innovation (info@Art-Innovation.nl)

- Cost action G7 meeting + workshop: Conservators and the use of laser
techniques in
conservation (18 October 2002, Vantaa, Finland). For more information
contact
Christian Degrigny (Christian.degrigny@iad.evtek.fi)

Abbreviations and acronyms

ARC: Atelier Regional de Conservation
CMA: Criminal museum in Athens
CRAE: Conservation-Restauration des objets Archéologiques et
Ethnographiques
CRCDG: Centre de Recherche pour la Conservation des Documents Graphiques

EVTEK: Espoo-Vantaa Teknillinen Ammattikorkeakoulu
FTIR: Fourrier Transformed Infrared
GCL: Graphitic Corrosion Layer
HEAA: Haute Ecole d´Arts Appliqués
HES: Hautes Etudes Supérieures
ICN: the Netherlands Institute for Cultural Heritage
MMF: Maritime Museum of Finland
MRT: Mission de la Recherche et de la Technologie, Ministère de la
Culture et de la
Communication
MsS: Master of Science
NMF: National Museum of Finland
PEG: polyethylene glycol
TEI: Technological Education Institute

Contacts

Tiina Andersson / EVTEK Institute of Technology
(tiina.andersson@kolumbus.fi)
Vasilike Argyropoulos / TEI of Athens (bessie@teiath.gr)
Christian Degrigny / EVTEK Institute of Art and Design (?:+358 9 511
9406 -
christian.degrigny@iad.evtek.fi)
Ilonne de Groot / ICN (gloond@hotmail.com)
Nathalie Huet / Arc´Antique (?:+33 2 51810940 - arcantique@wanadoo.fr)
Pia Klaavu / NMF (?:+358 9 405 9503 ? pia.klaavu@nba.fi)
Rami Kokko / NMF (rkokko@yahoo.com)
Martin Ledergerber / HEAA-HES de la Chaux-de-Fonds
(martin_ledergerber@hotmail.com)
Stéphane Lemoine / Arc´Antique (?:+33 2 51810940 -
arcantique.metaux@wanadoo.fr)
Jean-Bernard Memet /Arc'Antique (?:+33 2 51810940 -
arcantique.recherche@wanadoo.fr)
Malalanirina Rakotonirainy (rakotoni@cimrs1.mnhn.fr)
Loretta Rossetti / Arc´Antique (?:+33 2 51810940 -
arcantique.metaux@wanadoo.fr)
Quoc Khoï Tran / ARC-Nucléart ((?:+33 4 76884050  -
TRAN@chartreuse.cea.fr)

Correspondents

Australia: David Hallam, Canberra (d.hallam@nma.gov.au)
Belgium: Patrick Storme, Antwerpen (Patrick.storme@skynet.be) & Gilberte

Dewanckel, Bruxelles (gilberte.dewanckel@kikirpa.be)
Denmark: Karen Stemann Petersen, Copenhagen
(karen.stemann.petersen@natmus.dk)
France: Jean-Bernard Memet, Nantes (arcantique.recherche@wanadoo.fr) &
Régis
Bertholon, Paris  (bertholon7@aol.com)
Germany: Gerhard Eggert, Stuttgart (gerhard.eggert@abk-stuttgart.de)
Greece: Vasilike Argyropoulos, Athens (bessie@teiath.gr)
Italy: Paola Letardi, Genova (letardi@icmm.ge.cnr.it)
Netherlands: Bart Ankersmit, Amsterdam (bart.ankersmit@icn.nl)
Norway: Birgit Wilster-Hansen, Oslo (b.w.hansen@ukm.uio.no)
Spain: Emilio Cano, Madrid (ecano@cenim.csic.es)
Sweden: Helena Strandberg, Göteborg (helena.s@hem.utfors.se)
Switzerland: Valentin Boissonnas, La Chaux-de-Fonds
(v.boissonnas@heaa-ne.ch)
United Kingdom: David Thickett, London
(dthickett@thebritishmuseum.ac.uk)
USA: Paul Mardikian, Charleston (mardikian@hunley.org)