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Subject: Workshop on laser cleaning

Workshop on laser cleaning

From: Deborah Lau <deborah.lau>
Date: Wednesday, January 29, 2003
Laser Cleaning for Conservation
Melbourne May 19-23, 2003

Laser cleaning was first developed for architectural restoration. It
is also used commonly in the industrial environment and is promoted
as a means to remove contamination without modifying the underlying
surface structure of the material. Materials removed include:
rubber, demoulding agents, oil, grease, dust, organic pollutants,
oxides, rust, paint, varnish, atmospheric pollution and biological
or radioactive particles. Advantages are the absence of solvents,
detergents and water and most regions can be cleaned in situ,
without removal or disassembly.

The cleaning process is a photo-mechanical reaction. The incident
laser beam energises the first few microns of the surface of the
adhered material and converts it to a highly compressed plasma. The
plasma is a high-pressure, unstable ionised gas which, on expansion,
generates a shock wave that fragments the contaminant which is
volatilised. This process is also known as laser ablation.

The conditions of use must be optimised for each situation and laser
parameters such as wavelength, pulse duration, energy density,
spatial energy distribution need to be considered. When optimised,
the damage threshold of the contaminant is lower than the damage
threshold of the object being cleaned. As long as these conditions
are maintained, the laser will have no effect on the underlying
surface.

The use of lasers in conservation is justifiably approached with
caution to ensure the theoretical "zero substrate damage" ideal is
achieved. The issues of immediate chemical and structural alteration
(most often visible as colour change) and unnoticed long-term damage
are the prime areas of consideration for researchers working with
this application.

Laser cleaning has been successfully demonstrated for several
applications for conservation, especially on stone, metal and glass
surfaces, however there is a need for further investigation for
other objects comprised of complex materials. The advantages as a
cleaning treatment for conservators are the absence of solvents and
waste disposal, no abrasive damage as with sand or high pressure
water cleaning, increased ability to control removal rates, the
ability to focus down to spot sizes of less than 1mm, to selectively
remove dirt and retain patina, and a reduction in cleaning time of
up to 90%.

CSIRO have been investigating availability for conservators and
currently there are no facilities for laser cleaning of artworks and
architecture in Australia.  A portable system specifically designed
for conservation treatments, the Laserblast 50, is manufactured by
Quantel in France and exclusively distributed in Australia by
Coherent Scientific. It is a portable Nd:YAG  with fibre optic beam
delivery.

We now have the opportunity to host a 1 week workshop in Melbourne
to cover

    *   Cleaning procedure
    *   Maintenance
    *   Security issues
    *   General system use
    *   Hands on experience

Location: CSIRO, MIT, Graham Road Highett  Victoria AUSTRALIA 3190
Cost: $AU 1550

Concession: (full time students and unemployed) $AU 1150

For further information or for a registration form, please send
name, address, phone and email to:

    Deborah Lau
    Analytical and Conservation Scientist
    Materials Environment Interaction
    DBCE CSIRO
    PO Box 56
    Graham Rd
    Highett VIC 3190
    +61 3 9252 6403
    deborah.lau [at] csiro__au

Deborah Lau


                                  ***
                  Conservation DistList Instance 16:46
                 Distributed: Friday, January 31, 2003
                       Message Id: cdl-16-46-017
                                  ***
Received on Wednesday, 29 January, 2003

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