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Subject: Mold on paintings

Mold on paintings

From: Ercole Gialdi <>
Date: Monday, May 24, 2004
Ulrik Runeberg <rune-ulrik [at] gmx__de> writes

>I have been working during the past 10 months with a range of highly
>infested paintings (mostly acrylic on masonite, but also mixed media
>and oil on canvas), and try to inhibit the growth of mold with the
>application of thymol (dissolved in pure ethyl alcohol and applied
>with a spray gun on the reverse of the canvas/hardboard). ...

More than 10 years at, at RGI, the system VELOXY was developed,
tested and certified to solve the problem of insect pests in museums,
archives and libraries. (visit <URL:>).

Further research was done to minimise the risk of fungal infection
to artistic and historic collections. Find as follows the short
description of the outcome of the research done. I will be pleased
to show the photos of the tests done at the University of Rome La

In the atmospheric air, normally, there is a number of microorganisms
(mainly fungal spore and bacteria) which will fall down on the
surfaces with the powders suspended air; these microorganisms (upon
the environmental physical conditions) can rise serious fungal

The velocity of particles is proportional to their radius square
(from 2 to 20 micron in the case of spore and form 1 to 10 micron of
bacteria); they remain suspended until their velocity is lower to
the velocity of the ambient air.

The atmospheric concentration of fungi' spore depends on
meteorological conditions, seasons and the clime;  their number can
vary between 10.000 and 20.000 in a cubic meter of air and reach, in
some cases, the million.

The structures where the cultural heritage is conserved are
particularly threatened by microbial invasion because the velocity
of the air, inside the deposits, is scarce and, if the level of
humidity is high, the biological aerosol will surely raise an

The damage caused by fungal infections are serious and irreversible
and any action of disinfection will be taken, the problem will be
not overcome if the environmental conditions will remain the same.

It's worth noting that a high concentration of spore in the air is
also dangerous to human health because can cause asthma, allergies
and dermatitis.

At RGI a new method has been developed to protect the deposits where
the cultural heritage is conserved; both made of paper (libraries
and archives) and of wood and tissue (museums).

It is an equipment, called abios, by which the air is flown through
a labyrinth where it is exposed to an high energy UV radiation for a
time sufficient to reduce to zero the microbial activity of the
airborne powders.

The possible formation of traces of ozone is scarce because proper
optical filters have been adopted; in any case, a catalysts
(alumina, titanium and manganese) was installed to guarantee the
absence of this gas in the outlet stream of sterilised air (less
than 0,005 ppm).

The energy consumption of abios is 175 watt/hour and the air stream
that can be treated is more or less 100 m3/hour.

At the inlet of abios a filter was installed to stop the powder that
could reduce the sterilizing effectiveness of the UV generators;
this filter should be substituted every day so to guarantee the
integrity of the equipment.

The application of abios increases somehow the velocity of the
ambient air; this will contribute in the equipment efficacy because
an high velocity means to keep the aerosol suspended.

Are available the pictures that show the results of the tests
executed at the University of Rome La Sapienza (Laboratory of
Vegetal Pathology) they respectively are related to:

    Content of the spore in untreated air
    Content of the spore in the air at the middle of labyrinth
    Content of the spore in the air stream at the outlet of abios

Ing. Ercole Gialdi
RGI Resource Group Integrator srl
Viale Nazario Sauro 8
16145 Genova GE
+39 10 3626002
Fax: +39 10 3626799

                  Conservation DistList Instance 17:71
                   Distributed: Friday, May 28, 2004
                       Message Id: cdl-17-71-002
Received on Monday, 24 May, 2004

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