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RESEARCH STUDY ON THE EFFECTS OF THE THERMO LIGNUM® WARMAIR
TREATMENT ON ART OBJECTS WITH PAINT AND GILT FINISHES
Florian Tscherne* 1 , Bernhard Schachenhofer 2 , Karen Roux 3
1 Holzforschung Austria
2 Thermo Lignum® Österreich
3 Thermo Lignum UK Limited
Abstract
The present research study investigated the effects of a humidity controlled warm air treatment with the Thermo
Lignum Process on objects which are painted or gilded. The Thermo Lignum Process is an ecological and object
sensitive technique to combat insect infestations which applies only humidity controlled warm air. It is founded
on the established principle that most insects are reliably killed in all their life cycle stages at a temperature,
depending on species, of up to 55ºC. The infested objects are heated in a chamber to a maximum temperature of
58ºC. Throughout this process the air humidity is controlled in such a way that no drying of or changes in the
objects can occur. The objects prepared for the trial were examined before and after the Thermo Lignum
treatment by means of light microscopy and scanning electron microscopy. In addition, colour measurements
and investigations on potential distortion and adhesiveness to the substrates were carried out. In order to achieve
the most comprehensive and meaningful result, the trial was carried out with three different groups of objects.
Object Group One consisted exclusively of samples of the binding agents most commonly used in historic
finishes. Object Group Two included several newly applied finish layers, whilst Object Group Three comprised
historical objects with different finishes belonging to a variety of style periods.
1. Introduction
Art objects made of wood often suffer infestations by wood destroying insects (in particular by the
anobiidae species). The larvae of these woodborers eat through the timber frequently over several
years, and the adult beetles deposit their eggs preferably on the same objects, so that several
generations of insect can cause substantial and serious damage to objects. In order to preserve art
objects, a form of insect pest control is needed which has no negative effects on the objects requiring
treatment nor their constituent materials.
The Thermo Lignum® Warmair treatment offers an ecological alternative to the known conventional
eradication methods which count the fumigation of objects with toxic or inert gasses and the treatment
with liquid chemicals amongst them.
Applications for the Thermo Lignum® Warmair method to combat an insect attack in objects made of
materials as diverse as leather [1], paper [2], textiles [3], photographs [4] and so far as to include
insect collections [5], have already been sufficiently scientifically examined.
However, the behaviour of objects with surface finishes during a treatment with the humiditycontrolled
warm air method had not been sufficiently researched and documented to date, and this is
therefore the subject of this study.
2. Objectives
The main objective was to investigate the potential effects of a Thermo Lignum® Warmair treatment
on objects with paint and gilt finishes. The intention was, on the one hand, to examine, by means of
modern investigative methods, historical objects from a variety of style periods with varying finish
assemblies for potential changes caused by the Thermo Lignum® Warmair treatment. On the other
hand, the current study centred on potential modifications from such a treatment on the most
commonly used resins and glues (both individually as well as complete finishes) in the shape of newly
manufactured samples.
* E-mail: f.tscherne@holzforschung
Joseph Gril (edited by), Wood Science for Conservation of Cultural Heritage –Braga 2008: Proceedings of the International
Conference held by COST Action IE0601 (Braga - Portugal, 5-7 November 2008, ISBN 978-88-6453-157-1 (print)
ISBN 978-88-6453-165-6 (online) © 2010 Firenze University Press