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Laser cleaning of paper and parchment

Prototype laser cleaning system development for historical
paper and parchment including a catalogue of working
parameters to define the optimum conditions for application
by parchment and paper restorers.

Objective: The objective of the project is to develop a prototype laser cleaning system particularly fit for flexible paper and parchment cleaning. The design of this system has to be compact, easy to use and economical to allow operation by trained paper restorators at public and private institutions, e.g. archives, museums, collections, etc. The method will be based on the use of ultraviolet pulse lasers, ensuring the preservation of the delicate artefacts by minimising the absorption volume, the heat affected zone and the mechanical shock. Complementing the laser system, a catalogue of working parameters for typical artefact types, including for example optimum laser fluence ranges and damage threshold data, will be defined to allow the restorators to determine the optimum conditions for cleaning the objects in a minimum of time and with the utmost security of substrate preservation. On the basis of this research, the specifications for the laser cleaning system will be put in a call for tenders with the purpose of contracting the company with the best offer to build and market the instrument. Background: Cleaning of paper and parchment artefacts is necessary not only for aesthetic but also conservation reasons; any foreign material such as dirt can either serve as a culture medium for micro-organisms or can penetrate deeper into the material under increased humidity in the environment. Conventional mechanical and wet cleaning methods have proved insufficient in numerous cases as there are, for instance, brittle papers, fissures and sensitive inscripts. The main problem lies in the fibre structure of paper and parchment. Dirt and fluid cleaning media may irreversibly penetrate into the bulk structure where removal is either impossible or leads to mechanical or chemical destruction. Contactless cleaning, on the other hand, can be performed by applying short laser pulses in the nanosecond pulse duration regime. Fast removal of stains and dirt will be achieved by evaporation while inscripts are preserved and the composite structures consisting of protein or cellulose fibres remain chemically and structurally intact. This result will be achieved by ultimate confinement of the optical and thermal energy to a minimum volume in the foreign dirt phases. The use of ultraviolet laser light allows extremely small absorption depths, and choosing pulse durations of the order of 10 nanoseconds will reduce the heat affected zone to less than 10 um. The restoration and art history expert partners will define and select artefacts for which conventional techniques appear difficult or impossible. The laser technology partner will demonstrate the advantageous features of contactless laser cleaning, e.g. at fissures and bents, in the removal of foreign ink penetrated into white vellum areas, or removal of strongly adherent stain films on parchments. The evaluation of the test cleaning of selected artefacts will be done by microscopic and surface analytical inspection (scanning electron microscopy, scanning force microscopy, Fourier-transform-infrared microscopy, etc.). Keywords: laser cleaning, paper, conservation.
Acronym: 
LACLEPA
Project ID: 
1 681
Start date: 
01-01-1997
Project Duration: 
60months
Project costs: 
580 000.00€
Technological Area: 
Market Area: 

Raising the productivity and competitiveness of European businesses through technology. Boosting national economies on the international market, and strengthening the basis for sustainable prosperity and employment.