Modern architectural heritage protection in recent years has become a new hotspot
in the urban cultural heritage protection. The Chinese modern architectures
are the product of blending, collision between Chinese and western culture,
they have rich history and artistic connotation, among them there are a lot
of churches and independent of colonial style residential buildings. As they
are an indispensable part of the architectural language and the cultural relics
such as beautiful window, colored drawing or pattern glass and Mosaic glass
construction glass (historical architectural glasses), they ate the important
carrier of art architectural heritage value. But now the glass erosion of these
art works of Chinese architectural heritage is very serious and the rescue and
protection of them are very necessary and urgent. However, we often ignore the
deteriorating consequences they are facing.
The degradation mechanism of them, especially the mechanism of microbe degradation
research is developed insufficiently. And the past limited research is mainly
performed by foreign researchers, the research has been stagnated in recent
years and the similar research is almost blank in China. Therefore, the domestic
researchers of china should actively carry out targeted degradation mechanism
(including the microbial degradation) and cleaning technology development work
of the architectural heritage.
MICROBIAL DEGRADATION PHENOMENA OF THE CULTURAL RELIC ARCHITECTURAL GLASS
Definition of glass types and materials in cultural relic building:
Glass material is mainly used in doors and windows of the building. And the
cultural relic architectural glass discussed in this study, mainly refers to
the middle ages and modern European architecture, it is the important part of
the cultural heritage. The art glass has an independent artistic value is mainly
refers to color glass or glass mosaic.
Medieval stained glass mainly used in 13-15 century has two kinds: One
is the rich in sodium glass (which is stable, Mediterranean, similar to the
traditional roman style) and rich in potassium, calcium of glass (similar to
the central European Medieval stained glass) (Garcia-Valles
et al., 2003). And as known that from the Middle Ages to the Renaissance
period, the stained glass is generally applied in the church buildings and they
are made of potassium-lime-silicate glass (Carmona et
Microorganism degradation phenomenon in cultural relic building glass:
The glass microorganism degradation phenomenon is often neglected in the short
term; many professionals even think that there does not exist glass degradation
problem. Until now, there still doesn't get the full record about the microbial
activity to glass corrosion phenomenon. Only a few related researches in the
glass surface growth of microorganisms are published (Marvasi
et al., 2009). Actually, this kind of phenomenon, the slightly degradation
can be able to observed, such as the aquarium glass walls, fat, dust, moisture
and volatile component can lead to the adsorption and growth of the microbe
and glass surface will be corroded gradually and thus make glass surface eventually
appears close to the frosted glass (Krumbein and Gorbushina,
In the early days of observation, some researchers have noticed that the oligotrophic
microbes can live on the surface of seemingly no nutrition liquid and solid
such as metal and glass, etc. (Wainwright et al.,
1993), in the same historical building, the pitting corrosion structure
of glass microbial corrosion, grain and metabolites are very similar with marble
and limestone samples (Garcia-Valles et al., 2003;
Krumbein et al., 1991).
Koestler et al. (1987) found that only on the
glass surface of rich sodium, the breeding of microorganism is influenced by
the humidity, the greater the humidity is the microbial degradation phenomenon
is more serious; while the rich potassium glass in low humidity conditions (caused
by microbial reproduction) of flaking and fracture phenomenon does not appear
in high humidity conditions. Garcia-Valles et al.
(2003) made the related research on several churches in the Mediterranean
climate environment, the studies show that degradation of glass the surface
of which have rich potassium and calcium are in two forms, i.e., the dissolution
(the pitting in microscopic and mesoscopic) and its structural (product of which
is green rust and crusting), at the same time the thickness of glass main body
will become thinner.
In the corrosion process of stained glass windows, in the past, it is often
attributed to the chemical corrosion effect. At present, Valentin
et al. (1996) studied the Spain's cultural relics of the stained
glass windows and the related results of experiments show that under the condition
of appropriate relative humidity, the dust on the surface of the glass and the
condensate can lead to the development of microbial species and lead the degradation
of glass. In addition, Staudigel et al. (1995)
studied the nuclear waste glass surface exposed to seawater, the related experiments
also show that microorganisms in natural and synthetic glass play an important
role in the process of dissolving and microbial degradation caused by glass
is faster than most of the geological processes (geological the processes).
Therefore, microbial damage to the cultural relic architectural glass phenomenon
does exist; professionals engaged in the work of modern architectural glass
heritage protection should be paid great attention to microbial degradation.
MICROBIAL DEGRADATION MECHANISM OF CULTURAL RELIC ARCHITECTURAL GLASS
Microbial degradation form of cultural relic building: Through the research
analysis, Koestler et al. (1987) found that the
glass surface of the microbial growth has three different consequences: Erosion
surface or sub-surface directly, microbial adhesion phenomenon because mechanical
damage and the microbial membrane fixed continued to soak the substrate surface.
Gorbushina and Palinska (1999) summarized many cultural
relics and made the sample research of microbes on the architectural glass and
found that the surface of the microbial metabolism is the reason of biomineralization
deposition. And related results are that the fungi and algae (Cyanobacteria)
cause pitting corrosion and crack; cells, hyphae and cytoplasm membrane (cellulose)
filaments leaves scratches on the glass surface; the fungi or algae grows on
a glass surface leads to the color change.
Microbial degradation cause of architectural glass of cultural relics:
The understanding of microbial degradation of glass materials and its influence
factors has important significance on cleaning and protection of cultural relics.
Glass degradation mainly has three types, namely that the physical weathering,
chemical corrosion and microbial degradation and air pollution caused by the
modern industry and inappropriate cleaning measures also aggravate the deterioration
process of the architectural in glass cultural relics.
|| Bio-degradation mechanism of glasses
Krumbein et al. (1991) made the observational
study that glass degradation characteristics and patterns of the induced by
microbes and microbial pitting and one possible explanation is that the diffusion-finite
decomposition (DLD clutches) fractal dimension.
Gorbushina and Palinska (1999) experimental evidences
show that biomineralization deposition on the surface of glass is the metabolism
of microorganisms (fungi and algae). In order to make the convenience understanding
of architects and engineers working in the field of architectural heritage protection,
non-metallic inorganic materials, such as glass, microbial degradation mechanism
can be simply expressed in Fig. 1.
Recent comprehensive studies (Carmona et al., 2006;
Muller et al., 2001; Gorbushina
and Palinska, 1999; Drewello et al., 2000)
it can be confirmed that the glass of the degradation can be attributed to chemical
degradation process and the synergistic effect of microbial activity (synergistic
effects). And in the process of the synergistic effect, the chemical composition
of glass, which determine its durability or sensitivity to microbial corrosion,
the composition of biological membrane (which presents the strain specificity)
and the influence of climatic conditions in glass material and substrate surface
growth of microorganism degradation are the three decision factors. Previous
studies usually concern on the single microbe degradation effect and microbial
degradation and the synergistic effect between the physical weathering, chemical
corrosion is the research emphasis in the future.
Observation of microbial species: Glass surface morphology under normal
conditions should be smooth or nearly smooth, except some tiny pit, there is
heterogeneity of incrustation on the surface and often is full of white sediment.
In the early days, as the cultural relic architectural glass microbial degradation
is not got enough attention and experiment conditions is limited, the researchers
only can observe fungi and algae, but the lichen can not be directly identified
(Krumbein et al., 1991) . In recent years due
to the development of the surface analysis technique in the popularization and
application in the study of microbial degradation, researchers have realized
that microbial degradation bacteria on the surface of the glass is much more
complex than previously research results (Rolleke et
al., 1999). Schabereiter-Gurtner et al.
(2001) found that cultural relics architecture glass is the habitat of fungi
and bacteria, where has the high diversity of microbial consortium. The fungi
and bacteria are mainly as below, Aspergillus (Aspergillus), short shank mildew
genera (Aureobasidium), pear spore mould (Coniosporum), Capnobotryella (belong
to have silk spore fungus), lateral teeth white mold (Engyodontium), ground
wire mould (Geomyces), Kirschsteiniothelia phylum (belonging to the door plate
capsule), ball cavity bacteria genera (Leptosphaeria), rosolic saccharomyces
(Rhodotorula), Stanjemonium (belong to mitosis ascomycetes spores), Ustilago
(Ustilago) and cyclic bacteria genera (Verticillium). However, the research
of microbial community composition on glass surface where is dry environment
and with poor nutrition is less (Muller et al.,
Carmona et al. (2006) found the studied the
glass samples of 15th century charterhouse (Cartuja DE Miraflores, burgos province,
Spain) with external field emission scanning electron microscope examination
and found a large number of round and hollow pit, as well as many micro cracks
and fungal hyphae and conidium. Ecological niche hole detection, molecular recognition
and conidium morphology have shown that the microbiologically induced corrosion
of the glass main fungi is a. Tamari, also associated with other fungi and bacteria.
Marvasi et al. (2009) made the sample identification
to Florence cathedral, built in the 13th century cultural relics architecture
glass and study shown that the most representative bacterium is Bacillus genus
Bacillus, Bacillus (Arthrobacter) and Bacillus (Paenibacillus).
The cultural relic architectural glass of microbial identification results
show that the microbial proliferation affect on glass substrate degradation.
Summary: Above all, the microbial degradation impact of cultural relic
building glass is the falling of the transparency of the glass, decrease of
thickness and color changes in stained glass and so on. The main form is the
its degradation is the microbial membrane directly covering, microbial metabolites
and secretion of mineralized crusting, microbes to grow in the micro cracks
in caused by mechanical damage and microbial metabolites and secretion of acid
solution. Therefore, in the modern building, the actively research should be
conducted and cleaning technology of glass window should be adopted and the
research results should be popularized as soon as possible.
RESEARCH ON MICROBIAL DEGRADATION OF GLASS EXPERIMENT TECHNOLOGY
Traditional technology: The most important repair means of cultural
heritage is to realize the material degradation caused by microbes with early
recognition (Rolleke et al., 2000). Degradation
mechanism and protection technology research results depends not only on the
researcher's observation and thinking ability, but also restricted by experiment
technology and equipment. The traditional bacterial culture in degradation microbial
species identification and comparative test is a common method (Staudigel
et al., 1995). But the most basic observation method is still through
the optical microscope (Fekrsanati et al., 2001).
New molecular biology techniques: The thickness of Biofilm and microbial
components information provide the necessary research basis for optimizing the
window cleaning procedures and its protection strategy (Muller
et al., 2001). The microbial corrosion is a very complicated process,
it involves adsorption and breeding of microorganism, electrochemical corrosion
process and interface chemical process and many other factors affect it, in
order to obtain the microbial corrosion mechanism, the electrochemical method
sometimes are need to used in combination with other surface analysis method,
such as scanning electron microscopy, electron probe, find out the different
detection methods of correlation between the results (Liao,
2003). Application of the emerging technologies of molecular biology, the
microbial degradation mechanism research will have a great promoting to the
In optical analysis method of spectral analysis technology, the researchers
used the scanning electron microscope (SEM) (Koestler et
al., 1987) and the scanning electron microscope, X-ray microanalysis
(SEM, EDS) (Garcia-Valles et al., 2003) and
field emission scanning electron microscope (FE-SEM, field emission scanning
electron microscopy) (Carmona et al., 2006).
In addition the nucleic acid dye (Muller et al.,
2001). Confocal laser scanning microscope and X-ray diffraction technique
(XRD) (Garcia-Valles et al., 2003) are also
got a certain application in the field.
In the optical analysis method of spectral analysis technology, molecular probe
techniques is mainly adopted, such as ordinary electron microprobe analysis
and fluorescent tags rRNA target oligonucleotide probe technology (Muller
et al., 2001).
In the study of microbial community composition, polymer chain reaction and
degeneration gradient technique (PCR-DGGE) has been widely used (Carmona
et al., 2006; Marvasi et al., 2009;
Rolleke et al., 1999; Schabereiter-Gurtner
et al., 2001).
The special issue should be noticed is that when taking microbial samples,
all kinds of gel system should be used in cultural relics glass in order to
reduce toxicity, physical and chemical degradation and the potential risk of
cloured pattern layer breaking away from on the glass (Valentin
et al., 1996).
CLEANING METHOD OF CULTURAL RELIC ARCHITECTURE GLASS
Traditional method: The most meticulous work of uncovering original
appearance of the relics is to clean these scale due to microbial degradation
and the chemical and physical erosion and fouling. Over the past centuries,
the mechanical removal has certain damage function and the chemical cleaning
methods are adopted in the cleaning of the stained-glass windows. Todays
cleaning process should have two complementary objectives: One is to improve
the readability of the cultural relics of the glass and slow down the weathering
process and the second is the removal of corrosion fouling should not endanger
its artistic value at the same time.
According to this standard, the application of mechanical cleaning and improved
methods of cleaning solution or gel pad, has obvious shortages (Murcia-Mascaros
et al., 2008).
New cleaning technology: In the 2000, Drewello
et al. (2000) developted the use of excimer laser radiation eroded
relics biofilm on the glass. As known that the chemical stability of lower glass
will promote the growth of high density biofilm, which only can use cleaning
ways of high energy and high chemical stability of glass only allows the diffusion
of a two-dimensional plane of biofilm on the glass surface, thus it can be remove
with low energy density gently.
Drewello etc. found that decisive factor of the laser ablation effect on biofilm
is the composition of the biofilm and its accumulated moisture and the ability
to manufacture glass degradation metabolites and formation of the corrosion
potential. Almost at the same time, Fekrsanati et al.
(2001) also made the comparative study of removal effect of different wavelength
laser on microorganism of the glass surface. But the actual cleaning construction
glass fouling with laser technology is different from the test work in the laboratory;
equipment operational ability and its cost efficiency of factors limit the further
popularization and application of such technology.
In addition, Murcia-Mascaros et al. (2008)
proposed the method of dissolving calcium carbonate from the glass shell and
the optimization of sulfate solution. The system is through the continuous on-line
analysis of pH value, temperature and conductivity and calcium ion concentration
parameters, to monitor and control the whole cleaning process. The technical
scheme has the problem of high cost and difficult to promote application.
The recent research shows that almost all of glass material commonly used can
occur microbial corrosion. At present, although the microbial degradation of
glass materials has a preliminary understanding, but the research work of variety
synergistic effect of degradation in the field are needed in its further promoting.
Inheritance and protection of the modern architectural heritage is our historical
responsibility of each architects, engineers and related technical researchers.
Domestic researchers of China should carry out targeted degradation mechanism
analysis and study the cleaning and maintenance measures according to different
climate condition, the condition of air pollution and characteristics of cultural
relic building; with the guarantee of maintaining the light quality and art
display effect of art glass, the developing of easy operation, moderate cost,
no pollution and low contamination and reliable effect of cleaning technology
is very necessary. Even it can draw lessons from nanotechnology and glass coated/coating
technology and develop new research areas of the active glass degradation protection
In addition, as the architectural glass degradation in cultural relic is a
long-term, slow and imperceptible process, the degradation test of prevention
measures and repairing technique research are difficult to get reliable conclusion
in short time. Therefore, accelerated experiment method of researching glass
material degradation is very necessary, which can verify results of the study
for us in the shortest possible period.
This study is supported by National Natural Science Foundation of China (50778123/51178016).