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Certain deterioration factors for works of art and simple devices to monitor them
The International/ouvnalof
Museum Management and Curatorship (1986),li,295-300
Certain Deterioration Factors for Works of Art and Simple Devices to Monitor Them TOSHIKO KENJO
Introduction Nowadays, most facilities for the accommodation and display of works of art are constructed of concrete, not least for safety against fire and earthquakes. As a result, the moisture and alkaline particles emitted from the internal surfaces of a newly built concrete facility may affect adversely works of art placed within the structure. Indoor contaminants, which are volatile substances originating from the materials used for interior decoration (wood, coating materials and certain fresh building materials used for ceilings, floors, etc.) and fittings, may also have a far from negligible effect on works of art. Another deterioration factor always to be considered is illumination by natural daylight or artificial light. Such irradiation can cause textiles to become brittle and faded, paintings to discolour and coating materials like varnish to lose volatile components, decompose, and so on. Thus, in order to prevent works of art from being adversely affected by deterioration factors known to be inimical to their conservation, it is most important for us to discover the extent to which each factor affects the various artifacts. The present author has developed simple and inexpensive test strips for use in monitoring these factors. Contaminants
in the Atmosphere
When linseed oil impregnated paper (prepared by impregnating filter paper with linseed oil, i.e. the medium of oil-paintings) is hung in a newly constructed concrete building and kept under observation, its colour changes from the original pale yellow to the dark brown characteristic of exposure to fresh new concrete. One year later it changes to a lighter brown, and two years after construction the colour change is to a slightly deeper yellow only. The change in colour thus becomes less pronounced with the passage of time after construction. The same linseed oil impregnated paper, when kept in an unpolluted room with an ambient relative humidity in the range of 22-75 per cent, also changes from the original yellow to a lighter yellow colour as the humidity of the room is reduced. From scrutiny of the results gained from a series of tests, it was found that the colour changes observed in linseed-impregnated paper exposed within a concrete building two years after construction are quite similar to those kept in a clean-air environment. On this basis, it can be deduced that if a building is dried naturally for more than one and a half years the atmosphere within it can regain normal conditions. Subsequently, canvases which had been painted with various pigments were placed in a store with raw, exposed concrete walls and observed to see how they would change. As a 0260-4779/86/030295-06503.00
01986
Butterworth&Co(Publishers)Ltd
296
Simple Devices
to Monitor
Deterioration
Factors
result the changes shown in Table 1 were recognized. In such a room, with exposed fresh concrete walls, white, red, blue and violet pigments were found to be unstable, whilst silk also changed in colour from white to yellowish, and its tensile strength was reduced. Recently it has been found that when oil-paintings were allowed to stand in such a concrete building the linseed oil in the paintings became denatured, and it can thus be assumed that the combined alkaline contaminants and moisture derived from the concrete promoted deterioration by mechanisms such as the saponification of linseed oil. Factors which have an adverse effect on works of art are not limited to the volatile components of concrete but also include many materials used for fitting out the interiors. Conifer wood and, in Japan, cypress, particularly when fresh, emit significant amounts of volatile substances into the surrounding atmosphere. In an enclosed space these substances can become so abundant in the atmosphere as to cause smarting of the eyes, whilst the resinous substances emitted from cypress wood forms deposits on iron or copper plates. As the wood seasons, the resinous deposits diminish, but moisture continues to be emitted so that corrosion products containing resinous matter are formed on metal surfaces. Both concrete and conifer wood emit contaminants into their surrounding atmosphere when they are fresh, and the amounts emitted are reduced as they age. However, it takes a considerable length of time for them to become almost dry by natural processes alone, and, in practice, the use of kiln-dried wood for lining a store-room enables us to avoid the worst problems posed by the emission of volatile substances from the wood. Though it is still possible for transmission of moisture containing the alkaline contaminants emitted by the concrete to take place through the dried timber, to pollute the atmosphere in the store-room. In the last decade or so, particle board, which is made of wood chips coated with resin and pressed into sheets, has been widely used as a new building material. Until recently, little attention was paid to pollution of the atmosphere stemming from the adhesives used. Similarly, there is also evidence that the alkaline substances used as curing agents in adhesives employed for lining walls with fabrics and carpeting floors can be released during the drying and ageing of the adhesives used. New materials and floorings, therefore, should always be tested for potential contaminants, and not only themselves but also the adhesives used in conjunction with them.
Irradiation Displaying works of art to the public requires their illumination, and for this purpose both natural daylight and light from incandescent and fluorescent lamps have been used. These light sources have certain disadvantages, as they emit ultraviolet radiation or heat, both of which are potential hazards for works of art. Therefore, various modifications to remove these disadvantages are employed, but light itself, even if it has no thermal or ultraviolet components, can accelerate the deterioration of works of art, and simple convenient tools for monitoring the quantity of lighting or energy irradiating the works of art would be desirable.
Colour-changing
Test Papers
Four pH-indicators-Chlorophenol Red, Bromothymol Blue, Bromocresol Green and Phenol Red-are mixed to prepare test-paper strips to monitor contaminants in the atmosphere. Equal volumes of 0.5 per cent glycerol solutions of each indicator mentioned above are mixed, and the product is designated a colour-changing stock
297
TOSHIKO KENJO
solution. A sheet of filter paper is dyed with this stock solution and cut into strips 1 cm wide which are called ‘colour-changing test paper strips’. We can assess the characteristics of the atmospheric conditions in a store-room, show-case or display gallery after hanging the strips inside for 24 hours, according to the criteria in Table 1. Table 1. Colour Colour
of strip
Ambient
of colour-changing Orange
Red
conditions
Yellow
acidic
test strip and ambient Yellow-green
condition
Green
neutral
Blue-green
Blue
alkaline
To take one example: when the exposed surfaces of the concrete walls of one new store-room were covered with wooden panels we found that the strips hung inside the store-room showed the yellow colour corresponding to acidic air in the space, due to the presence of those wooden panels. Whilst without the panels the strips showed the green colour corresponding to alkaline air in the store-room. This test paper had turned blue-green in colour for a short period immediately after the store-room was completed, which indicated strongly alkaline conditions in the store-room then. By the time the building was handed over by the architect to the museum it showed a green colour. If oil-paintings had been kept in the store-room at such a time there would probably have been a discoloration of pigments and degradation of the linseed oil. But if the concrete is allowed to dry out, or if by some means the alkaline contaminants are removed, the colour strip will be yellowish-green, which indicates the atmosphere to be neutral. Linseed Oil Impregnated
Paper
These test-paper strips are prepared by impregnating filter paper with linseed oil and cutting it into 1 cm wide strips. The test paper is hung in the room under examination for 10 days and any change in colour is then measured using a colour meter to determine its yellow index (YI), as the measure of discoloration, as below: YI
=
1OOY -
84.672 (w h ere Y and 2 are tristimulus
values)
The linseed oil paper is used after it has been dried until its YI value is 20, and the relationship between the time elapsed from the casting of the concrete and the YI value of the test paper is shown in Table 2. Colour-changing test papers have the advantage of being able to respond in low and since, in fact, linseed oil paper is independent of ambient humidity conditions, humidity, it is desirable to use them in combination.
Table 2. Yellow index and colour of linseed oil strip and atmospheric
conditions
Yellow index
Colour
Atmospheric
conditions
Above 40 40-30 Below 30
Reddish-brown Brown Yellow to light yellow
One year after concrete construction Two years after concrete construction Atmosphere surrounded with wood
Simple Devices to Monitor ‘Deterioration Factors
298
Photo-monitoring
Test Strips
The present author has examined many dyestuffs and pigments for their fading discoloration behaviour when exposed to monochromatic light in the range 200-700 nm, and has developed two kinds of photo-monitoring test strips: Rhodamine test strips, and Litharge test strips.
Rhodamine
B Photo-monitoring
or of B
Test Strips
A 0.3 per cent solution of Rhodamine B (CI no. 45170) in aqueous alcohol (1 :l v/v) was prepared. A sheet of filter paper (Toyo Roshi no. 5) was immersed in the solution, any excess of the solution was blotted off, and the sheet was allowed to dry in the air in a dark room. Cut into strips 2 cm wide, these are designated Rhodamine B photo-monitoring test strips. Sample test strips were exposed to monochromatic rays in the range of 200-700nm employing an Xe lamp as the light source on a Model CRM-FA Diffraction grating spectroscope (manufactured by the Nihon Bunko Co.) and measured for colour difference from the unexposed strips after different lengths of time. The relationship between colour difference, AE of the test strips and irradiated energy is shown in Figure 1. This demonstrates that Rhodamine B test strips are very sensitive to the light below 284 nm, whereas they are fairly stable in light greater than 647 nm, and provide rather similar discoloration patterns in the range of 338-596 nm which includes the major part of the visible spectrum. The test strips, after irradiation from a non-ultraviolet fluorescent lamp (National FL40 SW. SDL-NU/M) gave AEtime curves shown in Figure 2, indicating the AE of the strips progressively increases with the increase in illuminance. This demonstrates that Rhodamine B test strips are well suited for monitoring visible light.
1 0
699
2 l 647 3 l
596
4
n
544
5 v
498
6
441
q
7 A 390 g .
338
9
A
284
10 0
235
Irradiated energy (lo7 erg cm-*)
Figure
1. Colour
difference
- irradiated energy curves of Rhodamine monitoring test strips.
B photo-
TOSHIKO KENJO
299
AE
0
100
200
300
400
500
600
700
800
900
1000
Time (h)
Figure 2. AE in Rhodamine
B monitoring
Litharge Photo-monitoring
strips - time curves when irradiated fluorescent lamp.
with a non-ultraviolet
Strips
Litharge (Special Grade Reagent, available from Wako Junyaku Co.) was mixed with a 10per cent aqueous solution of glue to make a soft paste. This paste was then applied to a paper board, cut into strips 2 cm wide, and dried in a dark place. These are designated as litharge photo-monitoring test strips. Sample strips were exposed to monochromatic rays in the range of 200-700 nm in the same manner as with the Rhodamine B test strips and colour difference, AE-, irradiated
6 2 3 4 5 6 7 8 9 10
25
8
16
24 Irradiated
Figure
3. Colour
32 energy
40
48
56
64
+ 647 . 596 n 544 v 498 q 441 A 390 v 338 A 284 0 235
72
(lo7 erg cm-‘)
difference - irradiated energy monitoring test strips.
curves of Litharge
photo-
300
Simple Devices
to Monitor
Deterioration
Factors
energy curves were obtained as shown in Figure 3. Unlike Rhodamine B test strips, Litharge test strips are fairly sensitive to ultraviolet rays and also to visible light below 441 nm, whereas they are relatively stable to visible light above 498 nm. Therefore, Litharge photo-monitoring test strips can be used for monitoring ultraviolet rays but they are poor for monitoring visible rays. As can be expected from the above results, the Litharge test strips did not respond to various non-ultraviolet lamps with different illuminance, as shown m Figure 4.
AE 200 Ix 400 Ix 600 Ix
8 15 ‘G I! lo8
I 0
l
t n
loo
200
I
I 300
I
loolx
”
I 400
I
I 500
I
I
I
600
11
700
1
coo
11
l
900
J
loo0
Time (h)
Figure
4. AE in Litharge
monitoring
strips - time curves fluorescent lamp.
when
irradiated
with
a non-ultraviolet
Simultaneous use of both photo-monitoring strip tests therefore enables on an individual basis ultraviolet rays and visible light at the same time.
us to monitor
Conclusion Four monitoring test strips have been developed, two for ambient contaminants and the other two for irradiation. These are characterized as very simple and cheap to use because there is no need for any expensive modern equipment, and the author has great confidence in their being well-suited for widespread use in monitoring the environment for the conservation of ancient and modern works of art. These four test strips have just started to come into general use in Japan, and thus there are still relatively few data available concerning their use in everyday conditions. The author believes, however, that many who are responsible for the conservation of works of art could use them to advantage.
Museum Management and Curatorship (1986),li,295-300
Certain Deterioration Factors for Works of Art and Simple Devices to Monitor Them TOSHIKO KENJO
Introduction Nowadays, most facilities for the accommodation and display of works of art are constructed of concrete, not least for safety against fire and earthquakes. As a result, the moisture and alkaline particles emitted from the internal surfaces of a newly built concrete facility may affect adversely works of art placed within the structure. Indoor contaminants, which are volatile substances originating from the materials used for interior decoration (wood, coating materials and certain fresh building materials used for ceilings, floors, etc.) and fittings, may also have a far from negligible effect on works of art. Another deterioration factor always to be considered is illumination by natural daylight or artificial light. Such irradiation can cause textiles to become brittle and faded, paintings to discolour and coating materials like varnish to lose volatile components, decompose, and so on. Thus, in order to prevent works of art from being adversely affected by deterioration factors known to be inimical to their conservation, it is most important for us to discover the extent to which each factor affects the various artifacts. The present author has developed simple and inexpensive test strips for use in monitoring these factors. Contaminants
in the Atmosphere
When linseed oil impregnated paper (prepared by impregnating filter paper with linseed oil, i.e. the medium of oil-paintings) is hung in a newly constructed concrete building and kept under observation, its colour changes from the original pale yellow to the dark brown characteristic of exposure to fresh new concrete. One year later it changes to a lighter brown, and two years after construction the colour change is to a slightly deeper yellow only. The change in colour thus becomes less pronounced with the passage of time after construction. The same linseed oil impregnated paper, when kept in an unpolluted room with an ambient relative humidity in the range of 22-75 per cent, also changes from the original yellow to a lighter yellow colour as the humidity of the room is reduced. From scrutiny of the results gained from a series of tests, it was found that the colour changes observed in linseed-impregnated paper exposed within a concrete building two years after construction are quite similar to those kept in a clean-air environment. On this basis, it can be deduced that if a building is dried naturally for more than one and a half years the atmosphere within it can regain normal conditions. Subsequently, canvases which had been painted with various pigments were placed in a store with raw, exposed concrete walls and observed to see how they would change. As a 0260-4779/86/030295-06503.00
01986
Butterworth&Co(Publishers)Ltd
296
Simple Devices
to Monitor
Deterioration
Factors
result the changes shown in Table 1 were recognized. In such a room, with exposed fresh concrete walls, white, red, blue and violet pigments were found to be unstable, whilst silk also changed in colour from white to yellowish, and its tensile strength was reduced. Recently it has been found that when oil-paintings were allowed to stand in such a concrete building the linseed oil in the paintings became denatured, and it can thus be assumed that the combined alkaline contaminants and moisture derived from the concrete promoted deterioration by mechanisms such as the saponification of linseed oil. Factors which have an adverse effect on works of art are not limited to the volatile components of concrete but also include many materials used for fitting out the interiors. Conifer wood and, in Japan, cypress, particularly when fresh, emit significant amounts of volatile substances into the surrounding atmosphere. In an enclosed space these substances can become so abundant in the atmosphere as to cause smarting of the eyes, whilst the resinous substances emitted from cypress wood forms deposits on iron or copper plates. As the wood seasons, the resinous deposits diminish, but moisture continues to be emitted so that corrosion products containing resinous matter are formed on metal surfaces. Both concrete and conifer wood emit contaminants into their surrounding atmosphere when they are fresh, and the amounts emitted are reduced as they age. However, it takes a considerable length of time for them to become almost dry by natural processes alone, and, in practice, the use of kiln-dried wood for lining a store-room enables us to avoid the worst problems posed by the emission of volatile substances from the wood. Though it is still possible for transmission of moisture containing the alkaline contaminants emitted by the concrete to take place through the dried timber, to pollute the atmosphere in the store-room. In the last decade or so, particle board, which is made of wood chips coated with resin and pressed into sheets, has been widely used as a new building material. Until recently, little attention was paid to pollution of the atmosphere stemming from the adhesives used. Similarly, there is also evidence that the alkaline substances used as curing agents in adhesives employed for lining walls with fabrics and carpeting floors can be released during the drying and ageing of the adhesives used. New materials and floorings, therefore, should always be tested for potential contaminants, and not only themselves but also the adhesives used in conjunction with them.
Irradiation Displaying works of art to the public requires their illumination, and for this purpose both natural daylight and light from incandescent and fluorescent lamps have been used. These light sources have certain disadvantages, as they emit ultraviolet radiation or heat, both of which are potential hazards for works of art. Therefore, various modifications to remove these disadvantages are employed, but light itself, even if it has no thermal or ultraviolet components, can accelerate the deterioration of works of art, and simple convenient tools for monitoring the quantity of lighting or energy irradiating the works of art would be desirable.
Colour-changing
Test Papers
Four pH-indicators-Chlorophenol Red, Bromothymol Blue, Bromocresol Green and Phenol Red-are mixed to prepare test-paper strips to monitor contaminants in the atmosphere. Equal volumes of 0.5 per cent glycerol solutions of each indicator mentioned above are mixed, and the product is designated a colour-changing stock
297
TOSHIKO KENJO
solution. A sheet of filter paper is dyed with this stock solution and cut into strips 1 cm wide which are called ‘colour-changing test paper strips’. We can assess the characteristics of the atmospheric conditions in a store-room, show-case or display gallery after hanging the strips inside for 24 hours, according to the criteria in Table 1. Table 1. Colour Colour
of strip
Ambient
of colour-changing Orange
Red
conditions
Yellow
acidic
test strip and ambient Yellow-green
condition
Green
neutral
Blue-green
Blue
alkaline
To take one example: when the exposed surfaces of the concrete walls of one new store-room were covered with wooden panels we found that the strips hung inside the store-room showed the yellow colour corresponding to acidic air in the space, due to the presence of those wooden panels. Whilst without the panels the strips showed the green colour corresponding to alkaline air in the store-room. This test paper had turned blue-green in colour for a short period immediately after the store-room was completed, which indicated strongly alkaline conditions in the store-room then. By the time the building was handed over by the architect to the museum it showed a green colour. If oil-paintings had been kept in the store-room at such a time there would probably have been a discoloration of pigments and degradation of the linseed oil. But if the concrete is allowed to dry out, or if by some means the alkaline contaminants are removed, the colour strip will be yellowish-green, which indicates the atmosphere to be neutral. Linseed Oil Impregnated
Paper
These test-paper strips are prepared by impregnating filter paper with linseed oil and cutting it into 1 cm wide strips. The test paper is hung in the room under examination for 10 days and any change in colour is then measured using a colour meter to determine its yellow index (YI), as the measure of discoloration, as below: YI
=
1OOY -
84.672 (w h ere Y and 2 are tristimulus
values)
The linseed oil paper is used after it has been dried until its YI value is 20, and the relationship between the time elapsed from the casting of the concrete and the YI value of the test paper is shown in Table 2. Colour-changing test papers have the advantage of being able to respond in low and since, in fact, linseed oil paper is independent of ambient humidity conditions, humidity, it is desirable to use them in combination.
Table 2. Yellow index and colour of linseed oil strip and atmospheric
conditions
Yellow index
Colour
Atmospheric
conditions
Above 40 40-30 Below 30
Reddish-brown Brown Yellow to light yellow
One year after concrete construction Two years after concrete construction Atmosphere surrounded with wood
Simple Devices to Monitor ‘Deterioration Factors
298
Photo-monitoring
Test Strips
The present author has examined many dyestuffs and pigments for their fading discoloration behaviour when exposed to monochromatic light in the range 200-700 nm, and has developed two kinds of photo-monitoring test strips: Rhodamine test strips, and Litharge test strips.
Rhodamine
B Photo-monitoring
or of B
Test Strips
A 0.3 per cent solution of Rhodamine B (CI no. 45170) in aqueous alcohol (1 :l v/v) was prepared. A sheet of filter paper (Toyo Roshi no. 5) was immersed in the solution, any excess of the solution was blotted off, and the sheet was allowed to dry in the air in a dark room. Cut into strips 2 cm wide, these are designated Rhodamine B photo-monitoring test strips. Sample test strips were exposed to monochromatic rays in the range of 200-700nm employing an Xe lamp as the light source on a Model CRM-FA Diffraction grating spectroscope (manufactured by the Nihon Bunko Co.) and measured for colour difference from the unexposed strips after different lengths of time. The relationship between colour difference, AE of the test strips and irradiated energy is shown in Figure 1. This demonstrates that Rhodamine B test strips are very sensitive to the light below 284 nm, whereas they are fairly stable in light greater than 647 nm, and provide rather similar discoloration patterns in the range of 338-596 nm which includes the major part of the visible spectrum. The test strips, after irradiation from a non-ultraviolet fluorescent lamp (National FL40 SW. SDL-NU/M) gave AEtime curves shown in Figure 2, indicating the AE of the strips progressively increases with the increase in illuminance. This demonstrates that Rhodamine B test strips are well suited for monitoring visible light.
1 0
699
2 l 647 3 l
596
4
n
544
5 v
498
6
441
q
7 A 390 g .
338
9
A
284
10 0
235
Irradiated energy (lo7 erg cm-*)
Figure
1. Colour
difference
- irradiated energy curves of Rhodamine monitoring test strips.
B photo-
TOSHIKO KENJO
299
AE
0
100
200
300
400
500
600
700
800
900
1000
Time (h)
Figure 2. AE in Rhodamine
B monitoring
Litharge Photo-monitoring
strips - time curves when irradiated fluorescent lamp.
with a non-ultraviolet
Strips
Litharge (Special Grade Reagent, available from Wako Junyaku Co.) was mixed with a 10per cent aqueous solution of glue to make a soft paste. This paste was then applied to a paper board, cut into strips 2 cm wide, and dried in a dark place. These are designated as litharge photo-monitoring test strips. Sample strips were exposed to monochromatic rays in the range of 200-700 nm in the same manner as with the Rhodamine B test strips and colour difference, AE-, irradiated
6 2 3 4 5 6 7 8 9 10
25
8
16
24 Irradiated
Figure
3. Colour
32 energy
40
48
56
64
+ 647 . 596 n 544 v 498 q 441 A 390 v 338 A 284 0 235
72
(lo7 erg cm-‘)
difference - irradiated energy monitoring test strips.
curves of Litharge
photo-
300
Simple Devices
to Monitor
Deterioration
Factors
energy curves were obtained as shown in Figure 3. Unlike Rhodamine B test strips, Litharge test strips are fairly sensitive to ultraviolet rays and also to visible light below 441 nm, whereas they are relatively stable to visible light above 498 nm. Therefore, Litharge photo-monitoring test strips can be used for monitoring ultraviolet rays but they are poor for monitoring visible rays. As can be expected from the above results, the Litharge test strips did not respond to various non-ultraviolet lamps with different illuminance, as shown m Figure 4.
AE 200 Ix 400 Ix 600 Ix
8 15 ‘G I! lo8
I 0
l
t n
loo
200
I
I 300
I
loolx
”
I 400
I
I 500
I
I
I
600
11
700
1
coo
11
l
900
J
loo0
Time (h)
Figure
4. AE in Litharge
monitoring
strips - time curves fluorescent lamp.
when
irradiated
with
a non-ultraviolet
Simultaneous use of both photo-monitoring strip tests therefore enables on an individual basis ultraviolet rays and visible light at the same time.
us to monitor
Conclusion Four monitoring test strips have been developed, two for ambient contaminants and the other two for irradiation. These are characterized as very simple and cheap to use because there is no need for any expensive modern equipment, and the author has great confidence in their being well-suited for widespread use in monitoring the environment for the conservation of ancient and modern works of art. These four test strips have just started to come into general use in Japan, and thus there are still relatively few data available concerning their use in everyday conditions. The author believes, however, that many who are responsible for the conservation of works of art could use them to advantage.