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Laser Cleaning of Art Works

#B-373.2


Laser Cleaning of Art Works of Metals, Paper, Parchment, Fabric, Leather and Painting: Research of Possibilities, Development of Technologies and Laser Equipment

Tech Area / Field

  • OTH-OTH/Other/Other
  • PHY-OPL/Optics and Lasers/Physics

Status
8 Project completed

Registration date
10.04.2001

Completion date
09.04.2007

Senior Project Manager
Novozhilov V V

Leading Institute
B.I. Stepanov Institute of Physics, Belarus, Minsk

Collaborators

  • National Museums and Galleries on Merseyside / The Conservation Centre, UK, Liverpool\nArt Innovation b.v., The Netherlands, Hengelo\nUniversity of Vienna, Austria, Vienna\nUniversity of Liverpool, UK, Liverpool\nInstitute of Electronic Structure & Laser, Greece, Heraklione\nLynton Lasers Ltd., UK, Ches, Wilmslow

Project summary

Objectives:

Objective of the project B-373-2 is to build novel portable customized robust laser systems appropriate for multipurpose applications in the field of art conservation for cleaning of art pieces of marble, other stones, paper, metal, archaeological, parchment, fabric, leather, and painting and testing them for cleaning of different art pieces in realistic environments.

For realizing the objectives, the next prototype YAG:Nd laser systems are supposed to be built. These systems will incorporate all achievements, experience and know-how of the Institute of Physics NANB.

The proposed systems are:

1. Energy stabilized compact robust YAG:Nd laser for 3-d harmonic 355 nm with energy up 200-300 mJ and repetition rate up to 3-5 Hz.

2. Energy stabilized YAG:Nd laser for 4-th harmonic 266 nm with energy up 100 mJ and repetition rate up to 3-5 Hz, and 2-nd harmonic 532 nm.

3. Specially developed add-on solid-state frequency converter.

Then, methods of fibre transportation of short powerful laser pulses, which will give possibility to expand the range of application of the above systems or other commercial systems, will be considered.

Testing the lasers in the frame of a laser cleaning installation for cleaning of different art pieces in realistic environments will be conducted.

State of Affairs in the Research Area:

From the birth of a laser cleaning method, a great variety of investigations were conducted in the countries of Western Europe (UK, Greece, Netherlands, Italy, France, Germany, Spain, and others), which revealed many of features of different wavelengths, duration, energy fluence for cleaning of different art objects. (See, e.g., Laser Cleaning in Conservation: An Introduction, Ed. Cooper, M.I., Butterworth-Heinemann, 1998; Proceedings of the International Conference LACONA III, Lasers in the Conservation of Artworks III, April 26-29 1999, Florence, Italy, Ed. Renzo Salimbeni and, Giorgio Bonsanti, Journal of Cultural Heritage).

For example, it is known about a wide application of YAG:Nd lasers of the nanosecond duration range, emitting on 1.064 mm, with multi-mirror hinged manipulators, for cleaning artworks made of stone and some other materials, and about usage of powerful UV excimer lasers for laser cleaning of paintings of large dimensions.

Nowadays fundamental investigations of FORTH shows that for some very important customized cases of cleaning it is necessary to have different wavelengths from IR to UV in nanosecond range of duration. This mostly concerns the removal of encrustation (black crusts, soil-dust and biological deposits) from some cases of marble and sandstone. (See, e.g., 1. Maravelaki-Kalaitzaki P., Zafiropulos V., Fotakis C., Excimer laser cleaning of encrustation on Pentelic marble: procedure and evaluation of the effects. Applied Surface Science, 148 (1999) 92-104. 2. Klein S., Stratoudaki T., Marakis Y., Zafiropulos V., Dickmann K., Comparative study of different wavelengths from IR to UV applied to clean sandstone. Applied Surface Science, 157 (2000) 1-6. 3. Klein S., Fekrsanati F., Hildenhagen J., Dickmann K., Uphoff H., Marakis Y., Zafiropulos V. Discoloration of marble during laser cleaning by Nd:YAG laser wavelengths. Applied Surface Science 171, 243-252 (2001)).

It was shown that third harmonic (355 nm) of YAG:Nd laser gives very encouraging results, as combines the self-limiting possibility of laser cleaning of the main frequency (1064 nm) with the absence of discoloration (so-called yellowing), which in many cases is aesthetically not acceptable.

In some cases second harmonic (532 nm) gives good results.

Necessity of working in rather hard realistic environments requires highly robust portable and energy stabilized YAG:Nd laser systems with 1064 nm, 532 nm and 354.6 nm, running at variable repetition rates.

FORTH's and our (on the phase of PDG B-373 project) investigations have shown that nowadays such lasers are absent at the market.

It is known that very good results are produced in laser cleaning of paintings with UV eximer lasers. A substantial drawback of these systems is their large dimensions, weight and difficulty in their transportation to different places. FORTH investigations show that stabilized YAG:Nd lasers with 4-th harmonic and high quality cross section distribution of laser beam could partly substitute UV eximer lasers in this field.

An additional aspect in laser cleaning of artworks is investigation on cleaning of various materials using different laser wavelengths and pulse duration that are not commercially available from YAG:Nd lasers. Such materials may include stone, metals, paper, parchment, fabric, glass, feather, leather, and painting.

Project Effect on the Research Area Progress:

Realization of the purposes of the project in the whole:

– will give, first of all, scientists and restaurateurs from EU quite new powerful energy stable portable robust YAG:Nd lasers for 3-d 355 nm and 4-th 266 nm harmonics, with possibility to have in one optical way 1064 nm, 532 nm, 355 nm, with possibility of effective frequency change with the help of solid-state add-on, suitable for cleaning of art pieces of marble, other stones, paper, metal, archaeological, parchment, fabric, leather, and painting in the frame of laser cleaning installations in realistic environmental conditions;

– will allow developing essentially new semi-destructive efficient cleaning techniques for artworks, for example, for ancient marble sculptures; establishing for each particular kind of art product the most optimum conditions providing best selectivity, locality and efficiency of pollution layer removal;

– will enable delivering of laser radiation to a treated object with the help of flexible fibers of significant length, expanding a application range for the installations (for example, using in cult structures and other places difficult of access).

Competence of Project Participants:

In the project, 36 persons of the technological personnel, experienced in laser physics, spectroscopy and restoration, including 7 doctors of sciences (among which are 6 professors), 7 candidates of physico-mathematical sciences, 4 candidates of technical sciences, 1 candidate of fine art, 17 persons with higher education will participate as the main executors. They have a good experience in development of powerful, stable, robust YAG:Nd lasers with efficient harmonic generators. They are also experts in methods of phase-conjugation, non-linear optics. Recently the participants of the project have fulfilled preliminary investigations on the laser cleaning of metal works of art, carried out a cycle of research on development of powerful YAG:Nd lasers intended for the 1.32-1.44 mm range with fiber transportation of radiation, developed a highly efficient SRS – laser and OPO for the range of 1.1-1.6 mm, and also shown the possibility of oscillation in completely solid-state systems at fixed wave lengths in the 0.3-0.8 mm range.

Expected Results and their Application:

The next main results will be obtained:

– Investigations aimed at development of optimal optical and structural schemes of energy stabilized compact robust YAG:Nd laser for 3-d harmonic 355 nm with energy up 200-300 mJ, the short-time energy stability of 3-d harmonic better than 10%, repetition rate up to 3-5 Hz, temperature working range of 10-35 °C, for laser cleaning installation will be fulfilled. The laser will be created, tested, improved and commercialized.

– Investigations aimed at development of optimal optical and structural schemes of energy stabilized YAG:Nd laser for 4-th harmonic 266 nm with energy up 100 mJ, the short-time energy stability of 4-th harmonic better than 10%, repetition rate up to 3-5 Hz, and 2-nd harmonic 532 nm, for laser cleaning installation will be fulfilled. The laser will be created on the base of previous one, tested, improved and commercialized.

– Investigation and optimization of optical schemes for generating a number of discrete wavelengths located in the 0.266-1.6 mm band by nonlinear solid-state optical conversion of radiation of YAG:Nd laser with harmonic generators as well as investigation of possibility of increase of energy of short pulses of YAG:Nd laser transported by flexible fibre will be fulfilled. Creating, handing over to collaborator, testing add-on nonlinear solid-state optical converter for YAG:Nd laser in realistic environment and its commercialization will be fulfilled. Investigation of possibility of development technique for on-line control of cleaning process with YAG:Nd laser with pulse duration in the range of several hundred microseconds will be conducted.

– Optimization of cleaning procedure for art pieces of bronze and other metals will be fulfilled.

Estimations show that in the case of participation of foreign collaborators in commercialization there is a significant sale potential of results of the project.

Meeting ISTC Goals and Objectives:

– The project will enable a group of highly skilled scientists, among which are 7 doctors of sciences (among which are 6 professors), 7 candidates of physico-mathematical sciences, 4 candidates of technical sciences, 1 candidate of fine art, 17 persons with higher education, engaged earlier, for the most part, in development of the military technologies, to use their knowledge, experience and previous designs for peace purposes.

– The project is aimed at development of new contemporary commercial laser products, which will promote transition of Belarus to market economy meeting civil needs.

– Realization of the purposes of the project will support the fundamental and applied investigations, and development of technologies in respect of solution of the global problem of preservation of cultural legacy.

– Realization of the project B-372-2 will promote integration of scientists from Belarus into the international scientific community in this field. The scientific results obtained at fulfillment of the project will be offered for the scientific publications.

– Received at fulfillment of the project proposal, the scientific and technical information will be used to convert the military industry of Republic of Belarus to production ensuring steady incomes and creation of new working places, not related to realization of arms systems, including ones of mass extermination, capable of getting into the regions with an unstable political and military situation.

– The financing countries will have an opportunity to use the results of the project fulfilment without supplementary expenses.

Scope of Activities:

The project will be realized by the Institute of Physics of NASB with engagement of representatives of the National Art Museum of Republic of Belarus (NAM), the Research Technological Enterprise "Belmicrosystems" of "Integral" Amalgamation (RTE) and the Experimental Design Bureau "Axicon" (EDB) of NASB, and other optics and electronics instrument-making firms.

The project is planned for three year’s period. The total amount of work will make 513.1 man-months.

Role of Foreign Collaborators:

Cooperation with foreign collaborators from Europe in the framework of the project is assumed to be in the following forms:

– the project Recipient’s representatives visiting foreign collaborators and the most known EU scientists in the field of laser conservation of art works of various genres, for familiarization with their achievements and discussing the results of fulfillment of the project;


– information interchange during realization of the project;
– giving explanations to the ISTC technical reports (quarter, annual, final and other);
– collaborators from FORTH are supposed to fulfil checking in Greece the energy stabilized compact robust YAG:Nd laser for 3-d harmonic 355 nm with energy up 200-300 mJ and repetition rate up to 3-5 Hz in the frame of a laser cleaning installation for cleaning of different art pieces in realistic environments;
– collaborators from Art Innovation are supposed to fulfil supervision of checking in Belarus the energy stabilized YAG:Nd laser for 4-th harmonic 266 nm with energy up 100 mJ and repetition rate up to 3-5 Hz, and 2-nd harmonic 532 nm, in the frame of a laser cleaning installation for cleaning of different art pieces of paper and painting in realistic environment;
– collaborators from National Museums and Galleries on Merseyside (NMGM) and Lynton Lasers are supposed to fulfil checking of add-on solid-state frequency converter and fibre transportation methods of short laser pulses in the frame of a laser cleaning installation for cleaning of different art pieces in realistic environment;
– collaborators will take part in preparing proposals on commercialization of equipment developed in the framework of the project
– participating in technical checks of activity under the project carried out by the ISTC employees;
– holding joint working seminar;
– preparing of joint publications.

Role of Partner:

There are no partners.

Technical Approach and Methodology:

The authors of the project in the course of preliminary investigations on the phase of PDG B-373, estimated different optical schemes of the lasers and came to the conclusion that for realization of tasks which were formulated by EU collaborators in respect of development of new customized lasers for cleaning installations, the best way is to use, first of all, a laser system consisting of an oscillator which emit low-energy laser pulses, with good angular and spatial distribution in the cross section of laser beam, and double-pass amplifier with phase conjugation on stimulated Brillouin scattering for compensation of thermo-optical distortion of YAG:Nd rods under powerful lamp pumping.

That is why main efforts in the frame of the project will be put on the proper choice of all conditions of amplification and phase conjugation for getting highly stable in energy and angular and spatial distribution of laser pulses of the fundamental (1064) frequency.

The proper choice of crystals, types of interaction and optical schemes for generation of second, third and forth harmonics will give required by EU collaborators laser parameters necessary for laser cleaning installations.

The proper choice of crystal, optical scheme, conditions of excitation will allow creation of highly efficient non-linear solid state frequency add-on converter for the YAG:Nd laser. Work on research of mechanisms of fiber destruction under action of UV-radiation and on optimization of laser radiation transportation will be conducted.

Testing laser installations in Belarus will be conducted on fragments of artworks of the scientific auxiliary fund stored in the NAM’s store-rooms.

Investigation of fragments of artworks by methods of X-ray analysis, Auger-spectroscopy, secondary ions mass spectroscopy, scanning and transmission electron microscopy and other physico-chemical methods before and after cleaning with the help of a YAG:Nd laser operating in various modes will allow development of optimum laser cleaning technologies for artworks as well as to studying the possibility of their preservation.

Work will be organized so that investigations in different directions will go in parallel to ensure the most quick and efficient end results.


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