Glastrup, Jens

Rasmussen, Kaare Lund

Ryhl-Svendsen, Morten

Skytte, Lilian

University of Southern Denmark Research Output

Syddansk Universitet
The Showcase containing the remains of the Danish King St. Knud the Holy (+AD1086)
Ryhl-Svendsen, Morten; Rasmussen, Kaare Lund; Glastrup, Jens; Skytte, Lilian
Publication date:
2011
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Citation for pulished version (APA):
Ryhl-Svendsen, M., Rasmussen, K. L., Glastrup, J., & Skytte, L. (2011). The Showcase containing the remains
of the Danish King St. Knud the Holy (+AD1086).
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Download date: 19. Apr. 2017
The air quality inside the showcase containing the remains of the Danish
King St. Knud the Holy (+AD 1086)
Morten Ryhl-Svendsen1,*, Jens Glastrup1, Lilian Skytte2 and Kaare Lund Rasmussen2
1National Museum of Denmark, Department of Conservation, Kgs. Lyngby, Denmark
2University of Southern Denmark, Department of Physics and Chemistry, Odense, Denmark
*Corresponding email: morten.ryhl-svendsen@natmus.dk
Keywords: exhibition display, wood off-gassing, church, reliquary, cultural heritage
1 Introduction
We have investigated the climate and air quality
inside and outside the glass showcase containing
a wooden coffin and the remains of the Danish
King St. Knud the Holy (+AD 1086), located in
Odense Cathedral, Denmark. The reliquary has
since 1833 been on display in the church. In
1874 the wooden coffin was placed inside a
metal and glass showcase, where it has been
kept until this day, i.e. some 137 years (Fig. 1).
It contains the Kings bones as well as several
textiles, and the wooden 10th century coffin with
metal decorations (Rasmussen et al., 1997).
As air contaminants in high concentrations will
deteriorate materials, e.g., corrode metals and
perish textile (Téterault, 2003), the level of
internal air pollution inside the showcase, and
the level of climatic interaction between the
showcase and the church room, was
investigated.
Fig. 1. The display case containing the reliquary
on public display in the church.
2 Materials/Methods
VOC’s were measured inside and outside the
showcase for 7 days, using Tenax TA diffusion
tubes (prepared and analyzed by Norwegian
Institute of Air Research). Organic acids (acetic
+ formic) were likewise sampled during a 7 days
period (IVL Passive Samplers by the Swedish
Environmental Institute). Ozone and nitrogen
dioxide was sampled for one month; inside the
display case, in the church room, and outdoors
(diffusion tubes by Gradko International Ltd.,
United Kingdom). All diffusion sampling was
performed in duplicate; the reported
concentrations are the average value plus/minus
one standard deviation.
At one occasion compounds in air were sampled
by exposing a solid-phase microextraction fiber
(SPME, type Carboxen/PDMS coating, Supelco
Sigma-Aldrich) to the air inside the showcase,
and with subsequently analysis by GC/MS. This
screening was not qualitative.
The air exchange rate of the showcase was
measured at using a CO2 sensor (2810 Analyzer,
Bacharach, Inc., USA) for the measurement of
the concentration decay rate of CO2 released at
once into the case from a compressed gas
cylinder.
The corrosivity of the air was determined by
exposing a 20 x 50 mm pure lead coupon inside
the showcase for one year (Merck lead foil 0.25
mm, no. 1.07365.0500 pro analysis). The
amount of corrosion was quantified by weighing
the coupon on a micro-balance before and after
the exposure (Ryhl-Svendsen, 2008).
3 Results and discussion
The main class of pollutants inside the showcase
was organic acids; the concentration of formic
acid was 270 (±18) µg/m3, and for acetic acid
2550 (±503) µg/m3. VOC’s (other than formic
and acetic acid) were found in a total
concentration of 2920 (±573) µg/m3 (toluene
equivalents); the main compounds being
tridecane, tetradecane, furfural, and acetonitrile.
By SPME also monoterpenes and phenoxy
derivatives were detected.
While the showcase maintained internally
generated compounds in high concentrations, at
the same time it retarded external pollutants
from entering as the showcase was rather
airtight. Ozone, which was present inside the
church room at about 5 µg/m3, was below the
limit of detection inside the showcase (Fig. 2).
The air exchange rate between showcase and
church room was 0.8 per day.
Fig. 2. The distribution of pollutants between
showcase, church room, and outdoor.
The lead coupon exposed inside the showcase
was after one year totally covered in a whitish
corrosion layer. The coupon gained weight
corresponding to 8.4 g per m2 surface, which,
compared to what is observed for normal room
conditions, suggests a highly corrosive
environment (Ryhl-Svendsen, 2008).
Increased ventilation would retard the build-up
of the high pollution level inside the showcase.
However, care should be taken at the same time
not to increase the ingress of dust. Increased
ventilation of the showcase can be achieved by
natural air movements (convection) if
ventilation holes were added to the case. The
glass showcase is placed on top of a wooden
plinth, in which a ventilation grille could
connect the inside of the showcase with room
air. To avoid dust the inside of the plinth should
house a filter, which the air stream should pass.
4 Conclusions
We find that a viable interpretation is that the
organic acids and furfural are derived from off-
gassing of the oak wood of the coffin, the
monoterpenes from resin in pine wood, and the
phenoxy derivatives from the deterioration of
lignin.
Air contaminants in high concentrations could
pose a potential hazard to the reliquary. The
acetic acid could deteriorate metals, the textiles
and the bones in the coffin.
Increased ventilation of the showcase would
avoid the build-up of internal pollutants inside
the showcase.
This study demonstrates how the air pollution
concentration may increase to an extreme level
in confined spaces, if at the same time a
pollution source is enclosed. This is the situation
for many museum showcases, e.g., if made of
wood.
5 References
Rasmussen, K.L., Bennike, P., Kjær, U., and
Rabek, U. 1997. Integrity and characteristics
of the bones of the Danish King St Knud (II)
the Holy (+AD 1086). Journal of Danish
Archaeology 13, 161-170.
Ryhl-Svendsen, M. 2008. Corrosivity
measurements of indoor museum
environments using lead coupons as
dosimeters. Journal of Cultural Heritage 9,
285–293.
Tétreault, J. 2003. Airborne Pollutants in Muse-
ums, Galleries and Archives: Risk
Assessment, Control Strategies and
Preservation Management. Ottawa:
Canadian Conservation Institute, 167 pp.


The Showcase containing the remains of the Danish King St. Knud the Holy (+AD1086)

Lund Rasmussen, Kaare

Skytte, Lillian

Ministry of Culture Research Portal

The Showcase containing the Remains of the Danish King St. Knud the Holy (+AD1086)

The Showcase containing the remains of the Danish King St. Knud the Holy (+AD1086)

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University of Southern Denmark Research Output

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Ministry of Culture Research Portal