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Fibers and Polymers 2013, Vol.14, No.9, 1581-1585 1581 Studying Irradiation Homogeneity in Light Aging for Historical Textile Conservation Khaled Elnagar*, Sameh M. Reda 1 , Harby E. Ahmed 2 , and Shady Kamal Textile Metrology Lab, National Institute for Standards, Alharam, Giza, Egypt 1 Radiometry Lab, National Institute for Standards, Alharam, Giza, Egypt 2 Faculty of Archeology, Cairo University, Giza, Egypt (Received January 27, 2012; Revised March 3, 2013; Accepted March 10, 2013) Abstract: Instrumental light aging is one of the most important tools for restoration and conservation of historical textiles. It used in testing stability of conservation materials, in addition to its lightening effect during the presentation in the museums. Light fading is an important tool for preparing the aged textile and other polymeric samples especially for archaeological conservation applications. Many fadometers do not give homogeneous exposure for all sample’s areas. This work studies the color changes of silk fabric dyed with turmeric (Curcuma longa L.) mordanted with alum or ferric sulfate. Color change was studied for the exposure periods ranged from five to hundred hours. Three positions of different irradiance levels were measured on the same sample namely (bottom, middle and upper). Individual color change for each position was recorded and studied. The results showed that there is non-homogeneous irradiance distribution due to different positions in fadometer or mordant used. Keywords: Light aging, Conservation, Silk, Mordant, Turmeric Introduction Developing and understanding of the causes and mechanisms of light fading of historical textile fibers dyed with natural dyes in museums have been the subject of substantial researches over the past 50 years [1-4]. The sensitivity of a particular dye depends upon the chemical structure of the dye. The fading process is rather complicated in practice because of oxygen which is involved in the process. It is a matter of the energy of the radiation and the absorption of the particular dye as well as the way in which the dyed material may be protected by other chemical substances that make the dyed material more fast to light [5-9]. The Illuminating Engineering Society (IES) defines Illuminants as relative spectral power distributions consisting of ultraviolet (UV), visible (VIS) and infrared spectral (IR) energies [10]. Visible spectrum is a small amount of energy ranges from 380 nm to 780 nm. UV energy ranged from 100 nm to 400 nm. IR energy ranges from 0.78 μm to 103 μm. Lighting an object involves the narrow band of wavelengths ranged from approximately 380-780 nanometers, Light is accompanied by small amounts of Infrared (IR) and Ultraviolet (UV). It is important to note that light contributes to vision and damage, whereas non-visible IR and UV contribute to damage, but not to vision. A simple formula puts the exposure effects into consideration. Light radiant energy damage to objects “When radiant energy is incident on the surface of a material, a portion of that energy is absorbed promoting two different processes: radiant heating effect and/or photochemical action [11]. Most of light fading and colour testing equipment are based on using daylight illuminant (D65) that corresponds to a mid-day sun in Western Europe/Northern Europe; hence it is also called a daylight illuminant. As any standard illuminant (it is represented as a table of averaged spectro- photometric data), any light source which statistically has the same relative spectral power distribution (SPD) can be considered a D65 light source. The name D65 suggests that the correlated color temperature (CCT) should be 6500 K. There are no actual D65 light sources, only simulators can be used [12-14]. The correlated color temperature (CCT) is a specification of the color appearance of the light emitted by a lamp, High pressure mercury lamps are widely used in the fading process [15]. This work aimed to study the homogeneity of irradiation for some silk fabric dyed with turmeric (Curcuma longa L.) natural dye mordanted with alum or ferric sulfate. The samples were assessed with respect to the color parameters and color difference in addition to light intensity at different irradiation positions in fadometer. Experimental Fabric Greek silk fabric supplied by TSIAKIRIS Co., Soufli- Greece. The fabric was indentified in Table 1. Turmeric dye (Curcuma longa L.), and of color index (C.I.) 75300, or “Natural Yellow 3” was purchased from the Egyptian local market. Mordents such as alum AlK(SO 4 ) 2 ·12H 2 O and ferric chloride FeCl 3 were supplied by Fluka. *Corresponding author: [email protected] DOI 10.1007/s12221-013-1581-6

Studying irradiation homogeneity in light aging for historical textile conservation

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Fibers and Polymers 2013, Vol.14, No.9, 1581-1585

1581

Studying Irradiation Homogeneity in Light Aging for Historical Textile

Conservation

Khaled Elnagar*, Sameh M. Reda1, Harby E. Ahmed

2, and Shady Kamal

Textile Metrology Lab, National Institute for Standards, Alharam, Giza, Egypt1Radiometry Lab, National Institute for Standards, Alharam, Giza, Egypt

2Faculty of Archeology, Cairo University, Giza, Egypt

(Received January 27, 2012; Revised March 3, 2013; Accepted March 10, 2013)

Abstract: Instrumental light aging is one of the most important tools for restoration and conservation of historical textiles. Itused in testing stability of conservation materials, in addition to its lightening effect during the presentation in the museums.Light fading is an important tool for preparing the aged textile and other polymeric samples especially for archaeologicalconservation applications. Many fadometers do not give homogeneous exposure for all sample’s areas. This work studies thecolor changes of silk fabric dyed with turmeric (Curcuma longa L.) mordanted with alum or ferric sulfate. Color change wasstudied for the exposure periods ranged from five to hundred hours. Three positions of different irradiance levels weremeasured on the same sample namely (bottom, middle and upper). Individual color change for each position was recordedand studied. The results showed that there is non-homogeneous irradiance distribution due to different positions in fadometeror mordant used.

Keywords: Light aging, Conservation, Silk, Mordant, Turmeric

Introduction

Developing and understanding of the causes and mechanisms

of light fading of historical textile fibers dyed with natural

dyes in museums have been the subject of substantial

researches over the past 50 years [1-4]. The sensitivity of a

particular dye depends upon the chemical structure of the

dye. The fading process is rather complicated in practice

because of oxygen which is involved in the process. It is a

matter of the energy of the radiation and the absorption of

the particular dye as well as the way in which the dyed

material may be protected by other chemical substances that

make the dyed material more fast to light [5-9].

The Illuminating Engineering Society (IES) defines

Illuminants as relative spectral power distributions consisting of

ultraviolet (UV), visible (VIS) and infrared spectral (IR)

energies [10]. Visible spectrum is a small amount of energy

ranges from 380 nm to 780 nm. UV energy ranged from

100 nm to 400 nm. IR energy ranges from 0.78 µm to 103 µm.

Lighting an object involves the narrow band of wavelengths

ranged from approximately 380-780 nanometers, Light is

accompanied by small amounts of Infrared (IR) and

Ultraviolet (UV). It is important to note that light contributes

to vision and damage, whereas non-visible IR and UV

contribute to damage, but not to vision. A simple formula

puts the exposure effects into consideration.

Light → radiant energy → damage to objects

“When radiant energy is incident on the surface of a

material, a portion of that energy is absorbed promoting two

different processes: radiant heating effect and/or photochemical

action [11].

Most of light fading and colour testing equipment are

based on using daylight illuminant (D65) that corresponds to

a mid-day sun in Western Europe/Northern Europe; hence it

is also called a daylight illuminant. As any standard

illuminant (it is represented as a table of averaged spectro-

photometric data), any light source which statistically has

the same relative spectral power distribution (SPD) can be

considered a D65 light source. The name D65 suggests that

the correlated color temperature (CCT) should be 6500 K.

There are no actual D65 light sources, only simulators can

be used [12-14]. The correlated color temperature (CCT) is a

specification of the color appearance of the light emitted by

a lamp, High pressure mercury lamps are widely used in the

fading process [15].

This work aimed to study the homogeneity of irradiation

for some silk fabric dyed with turmeric (Curcuma longa L.)

natural dye mordanted with alum or ferric sulfate. The

samples were assessed with respect to the color parameters

and color difference in addition to light intensity at different

irradiation positions in fadometer.

Experimental

Fabric

Greek silk fabric supplied by TSIAKIRIS Co., Soufli-

Greece. The fabric was indentified in Table 1.

Turmeric dye (Curcuma longa L.), and of color index

(C.I.) 75300, or “Natural Yellow 3” was purchased from the

Egyptian local market.

Mordents such as alum AlK(SO4)2·12H2O and ferric

chloride FeCl3 were supplied by Fluka.*Corresponding author: [email protected]

DOI 10.1007/s12221-013-1581-6

1582 Fibers and Polymers 2013, Vol.14, No.9 Khaled Elnagar et al.

Dyeing

Dye Extraction

Turmeric roots were grinded into a fine powder, and

soaked in water (10 % w/v) for 24 h. and followed by

heating to boil for two hours. with continuous stirring. It

may require adding water to compensate the evaporated

water during the heating process. Finally allow the extract to

be cooled then filtered many times to get a clear colored and

transparent solution.

Dyeing Procedure

The dyeing was performed by the simultaneous dyeing

and mordanting technique [16]. In this method a liquor ratio

(LR) of 1:20 was used (For 1 g of good we use bath volume

of 20 ml). 10 grams of degummed silk fabric were used as

protein fiber substrate. The dyeing experiments were performed

in beakers according to the temperature-dyeing diagram

given in Figure 1. Liquor ratio (LR) was adjusted to be 1:20.

Mordants namely alum AlK(SO4)2·12H2O and ferric chloride

FeCl3 concentrations were adjusted to give a final concen-

tration of 0.5 % (owf). After dyeing, the unfixed dyestuff

was removed by rinsing three times with cold water (5 min,

room temperature, LR 1:20) [17-21].

Light Aging Instrument (Phadometer)

The samples in fading machine (phadometer) showed in

Figure 2.

The light source used was Mollar lamp 500 W self-ballasted,

Mix-light, Fluorescent coated. The separation between the

vertical axis of the lamp and the cylinder carrying the

samples is 33 cm. The UV irradiance level in µW/cm2 at

different sample positions measured using National Institute

for Standards (NIS) reference radiometer UDT 268-UVA

whose maximum spectral responsivity is located at 365 nm.

Also the total spectral power distribution of the lamp

measured using NIS grating monochromator (Newport

77000) resulting in 7.2 % of the output of the lamp is UVA

(315-400 nm) as CIE color system definition.

Color Measurement

The CIE-Lab. values of the color changes were measured

using double beam Optimatch spectrophotometer (Datacolor

international Spectraflash SF450-UK). The colors are given

in “Commission International de l'Eclairage” (CIE) Lab

coordinates, (L) : brightness (100=white, 0=black), (a) : red-

green coordinate (positive sign=red, negative sign=green),

and (b) : yellow-blue coordinate (positive sign=yellow, negative

sign=blue) [22,23].

L*=116(Y/Yn)1/3−16 (1)

a*=500[(X/Xn)1/3−(Y/Yn)1/3] (2)

b*= 200[(Y/Yn)1/3−(Z/Zn)1/3] (3)

∆E* = {(∆L*)2 + (∆a*)2 + (∆b*)2}1/2 (4)

Where Xn, Yn and Zn of the not-irradiated samples before

light aging. Y, X and Z are the color coordinates of the

samples at every irradiation period. These equations were

used in the spectrophotometer software to calculate the color

differences.

Results and Discussion

Spectral Distribution

The spectral power distribution specifying the lamp used

in this work is described in Figure 3. It is measured by NIS

facility of spectral power distribution system based on single

monochromator Newport model 77700.

The spectral distribution of the lamp clarify that the lamp

emits power at wide spectrum from ultraviolet to infrared.

The lamp output is 8.0 % ultraviolet, 48.0 % visible, and

43.0 % near infrared. The regions responsible for the most

Table 1. Fabrics structure of Silk dyed fabric that used in experimental part

Samples Thread (cm) Mechanical parameter [24] Weight

(g/m2)Weaving structure

Warp Weft Tensile force (kg·f) Elongation (%)

Uncolored silk 32 25 27.967 15.85225.4

Plain weave

1\1Silk-Turmeric 32 25 25.959 12.821

Figure 2. Schematic diagram of the illumination areas in the

phadometer (lamp located in the center of cylindrical shape).

Figure 1. Temperature time diagram of the one-bath dyeing process.

Light Aging Fibers and Polymers 2013, Vol.14, No.9 1583

detoriations in the sample are found to be the UV and IR

regions.

Irradiance Homogeneity

The irradiance levels in µW/cm2 at three positions top,

middle and bottom for the 12 samples positions of the fading

machine were measured using NIS reference radiometer

268-UVA. Figure 4 shows non-homogeneous relation between

the average levels and the positions indicating that the

highest irradiance level in our case (≈31,000±403 µW/cm2)

while the lowest irradiance level was (≈28,000±616 µW/

cm2) obtained at the top of the sample. This finding may be

attributed to the lamb configuration and irradiance distribution

of the bulb in addition to the lamp temperature inhomogenity.

The color difference of three locations on the same

samples was calculated at different exposures' time and it

was clear that the middle position on the samples showed the

maximum deterioration. This can be attributed to the fact

that of the inverse relationship between distance of

illuminant to the sample and the intensity as stated in the

following inverse square law [25].

Where E is irradiance and I is Light intensity.

For better fastness to light and washing, the use of

mordants may be essential for most of natural dyes. The

function of the mordant is to assist the adsorption of the dye

and promote good bonding of dye and fiber as a bridge,

which helps to bond fiber and natural dyes at the molecular

level [15]. In this work two mordants were used namely Fe

and Al mordants. The studied two mordants show different

photofading responses of the turmeric dyeing. Figures 5 and

6 show that the sample mordanted with alum is sensitive to

its position inside the fadometer than those of iron mordanted

samples [26,27]. Aluminum salt produces lower light stability

than ferric salt. This result may be attributed to the capability

of aluminum salt to form weak coordination complexes with

the dye, leading to quite strong bonds with the dye but not

with the fiber. Thus they block the dye and reduce its

interaction with the fiber [15].

Data in Table 2 shows the effect of the exposure period on

the studied phadometer at three different positions studied

for silk fabric samples dyed with turmeric dyes mordanted

with alum. Lightness value ‘L’ for all studied positions

(bottom, middle and top) is increased with the increase of

exposure time and this can be attributed to the degradation of

the chromospheres in the turmeric dye. Values of the red-

green component ‘a’ show changes from green to red

(hypsochromic shift with shorter exposure period of 10 hours

EI

r2

----=

Figure 3. Spectral power distribution of 500 W Mix-light Mollar

lamp.

Figure 4. Relation between the irradiance levels and their

locations on the sample compartment.

Figure 5. The color difference for different exposure time for

turmeric natural dye mordanted with Alum.

Figure 6. Color difference (∆E) for different exposure time for

turmeric natural dye mordanted with ferric mordant.

1584 Fibers and Polymers 2013, Vol.14, No.9 Khaled Elnagar et al.

maximum. Extended exposure period of the samples shows

more reddish color (bathochromic shift). Value of yellow

blue component indicates that the sample colors are shifted

to less yellow [28,29]. Data in Table 3 show that by increasing

the exposure period, brightness value ‘L’ increased and the

yellowish brown sample’s color decreased. Red -green

component ‘a’ values shifted to green color component. This

can be attributed to the molecule transitions to a shorter

wavelength due dye degradation and low stability of the

curcumin molecules (Figure 7) to day light. It is well known

that the dye on drying conditions turned to keto chemical

form, this chemical structure change accompanied with

colour changes depend on the extension of the light

exposure periods from 0 to 100 hours [29,30].

Conclusion

In conclusion, it can be seen that silk fabrics dyed with

Turmeric dye mordanted with different mordants are

affected by the position (Irradiance homogeneity) in the

phadometer and in turn the irradiation homogeneity. All

interested conservation and metrological textile scientists

should be aware that the location of the tested samples inside

the fadometer must be taken into consideration in addition to

type of mordant used the light ageing conditions (e.g., the

illumination source and its spectral power distribution) as

well as its distance to the tested samples. To achieve a

uniform light radiation of a light guide, it is very useful to

use a diffuser front of the radiating side. With a diffuser foil

a uniform and vectored radiation is achieved.

Acknowledgements

The work was performed at Textile Metrology and

Radiometry laboratories in the National Institute for Standards,

Giza Egypt. The authors wish to thank Eng. Rasha Sadek

Table 2. Color parameters (L), (a) and (b) for the three positions on the same samples dyed with turmeric natural dye and mordanted with

Alum after exposure periods in phadometer

Exposure

period (hour)

Top position Middle position Bottom position

L (a) (b) L (a) (b) L (a) (b)

0 79.53 -1.35 57.46 78.31 -0.91 58.02 78.86 -1.86 61.26

5 78.32 1.16 38.61 78.29 0.78 38.27 71.24 2.41 49.81

10 80.06 1.12 30.34 80.16 1.24 29.65 80.35 0.92 28.47

20 81.24 1.05 24.93 81.78 1.19 24.07 81.54 0.77 22.92

40 81.87 0.76 25.63 81.73 0.78 25.63 82.06 0.49 24.28

60 83.18 0.27 21.71 83.14 0.36 21.83 83.34 0.14 20.47

80 82.99 0.35 21.82 83.32 0.32 21.63 83.76 0.14 20.13

100 82.44 0.11 21.06 82.37 0.07 20.85 83.50 -0.05 19.67

Tables should be followed by their keys (e.g., L for lightning, a red-green, b yellow-blue).

Table 3. Color parameters L, a and b for the three positions on the same samples dyed with turmeric natural dye and mordanted with Ferric

sulfate after exposure periods in phadometer

Exposure

period (hour)

Top position Middle position Bottom position

L (a) (b) L (a) (b) L (a) (b)

0 80.57 1.50 63.07 80.38 1.08 62.33 80.42 0.30 63.65

5 81.24 2.27 37.35 82.19 1.76 37.24 41.89 2.61 -23.47

10 82.93 1.92 27.18 82.63 1.96 27.02 83.25 1.60 26.61

20 84.04 1.14 22.77 83.55 1.25 22.84 84.31 1.05 22.55

40 84.49 0.79 23.70 84.16 0.81 23.43 83.62 0.75 23.43

60 85.55 -0.04 21.07 85.12 0.14 21.20 84.46 -0.04 20.74

80 85.35 -0.02 21.02 85.25 0.05 20.90 85.11 -0.06 20.35

100 84.32 -0.26 21.17 84.04 -0.23 20.38 83.59 -0.26 20.01

Tables should be followed by their keys (e.g., L for lightning, a red-green, b yellow-blue).

Figure 7. Curcumin in Turmeric keto- and enol forms.

Light Aging Fibers and Polymers 2013, Vol.14, No.9 1585

from textile metrology Lab., for her contribution in the

experimental part.

References

1. M. Colombini, A. Andreotti, C. Baraldi, I. Degano, and J.

ucejko, Microchem. J., 85, 174 (2007).

2. K. Kato and R. Cameron, Cellulose, 6, 23 (1999).

3. C. Clementi, W. Nowik, A. Romani, F. Cibin, and G.

Favaro, Analytica Chimica Acta, 596, 46 (2007).

4. M. Muller, B. Murphy, M. Burghammer, C. Riekel, E.

Panto, and J. Gunneweg, Appl. Phys. A, 89, 877 (2007).

5. L. Kronthal, J. Levinson, C. Dignard, E. Chao, and J.

Down, J. Am. Inst. Conserv., 42, 341 (2003).

6. J. Down, M. MacDonald, J. Tétreault, and R. S. Williams,

Studies in Conservation, 41, 19 (1996).

7. J. Johnson, S. Heald, K. Mchugh, E. Brown, and M.

Kaminitz, J. Am. Inst. Conserv., 44, 203 (2005).

8. A. Emsley and R. Heywood, Cellulose, 4, 1 (1997).

9. W. Zainuddin, T. Le, Y. Park, T. Chirila, P. Halley, and A.

Whittaker, Biomaterials, 29, 4268 (2008).

10. CIE 103 Technical Report, Colour Appearance Analysis,

Technical Collection, 1993.

11. M. B. Gotti and S. Sedlak, “Light Sources and Dye

Fading”, GE Lighting, 2009.

12. N. Ohta and A. R. Robertson, “Standard and Supple-

mentary Illuminant”, pp.92-96, Colorimetry, Wiley, 2005.

13. J. Schanda, “CIE Colorimetry”, pp.43-44, Colorimetry:

Understanding the CIE System. Wiley, 2007.

14. CIE Technical Report, A Method for Assessing the Quality

of Daylight Simulators for Colorimetry, 1999.

15. V. Mirkhani, S. Tangestaninejad, M. Moghadam, M. H.

Habibi, and A. R. Rostami-Vartooni, J. Iran. Chem. Soc.,

6, 578 (2008).

16. M. M. Kamel, F. Abdelghafar, and M. M. Wl-Zawahry, J.

Natural Fibers, 8, 289 (2011).

17. T. Bechtold, A. Turcanu E. Ganglberger, and S. Geissler, J.

Cleaner Production, 11, 499 (2003).

18. H. Schweppe, “Practical Hints on Dyeing with Natural

Dyes”, Washington DC USA, 1986.

19. H. Schweppe, “Practical Information for the Identification

of Dyes on Historical Textile Materials”, Washington DC

USA, 1988.

20. H. Ahmed, Y. Zidan, and Kh. El-Nagar, “Proceeding of

First Annual AHRC Conference”, pp.246-250, UK, July

13-15, 2005.

21. S. Adeel, J. A. Bhatti, Kh. EL-Nagar, M. M. Alam, and N.

Ali, Res. J. Textile and Apparel, 15, 71 (2011).

22. G. Wyszecki and W. Stiles, “Color Science Concepts and

Methods”, 2nd ed., Quantitative Data and Formulae, New

York, 2000.

23. J. Booth, “Principles of Textile Testing”, Butterworth-

Heinemann, USA, 1984.

24. P. Tortora and R. Merkel, “Fairchild's Dictionary of

Textiles”, Fairchild's Books & Visuals-7th Edition, 2007.

25. G. C. Goats, Physiotherapy, 74, 8 (1988).

26. G. H. Robinson, “Coordination Chemistry of Aluminum”,

John Willey UK, 1993.

27. http://www.chemguide.co.uk/inorganic/complexions/whatis.

html access date 22/01/2012

28. Kh. El-Nagar, S. Sand, A. Mohamed, and A. Ramadan,

Polymer-Plastic Technology and Engineering, 44, 1269

(2005).

29. C. Reichardt, Chem. Rev., 94, 94 (1994).

30. E. M. Osman, S. F. Ibrahim, and M. N. Michael, Elixir

Chem. Phys., 35, 2777 (2011).

L