·Table of Contents
·Conservation and Restoration in Art and Architecture
Microbiological testing of Polymers and resins used in conservation of Linen TextilesOmar Abdel-Kareem
Microbiology Dept., Cracow Univ. of Economics, ul. Sienkiewicza 5, 30-033 Krakow, Poland
Permanent address: Conservation Dept., Faculty of Archaeology, Cairo Univ., Egypt.
This study tends to evaluate the most suitable and effective polymers and resins that can be applied safely and successfully in treating ancient Egyptian linen textiles. This paper is drawn from a larger research project. More detailed descriptions of testing procedures and an indeapth discussion of the results can be found in Abdel-Kareem,s thesis.
Polymers and Resins:
Selected polymers and resins are currently used in conservation of archaeological textiles, or materials that could be used in the future for the same purpose (See Table 1), (Abdel-kareem, 2000).
|Chemical Name||Trade Name||Producer||Conc %|
|1||Vinyl acetate/acrylic ester copolymer||Mowilith DM5 (E)||Hoechst||10|
|2||Vinyl acetate/dibutyle maleate copolymer||Mowilith DMC2 (E)||Hoechst||10|
|3||Ethyl acrylate/ methyl methylacrylate||Paraloid B72 (SD)||Rohm and Hass]||6|
|4||Butyl acrylate/ methyl methylacrylate||Lascaux 360 HV (E)||Lascaux Restauro||10|
|5||Ethyl acrylate/ methyl methylacrylate||Plextol B-500 (E)||Lascaux Restauro||10|
|6||Butyl methylacrylate||Acryloid F-10 (SN)||Rhom and Haas||10|
|7||Butyl methylacrylate||Plexisol P-550 (SN)||Lascaux Restauro||10|
|8||Soluble nylon||Calaton CA (SD)||Imperial Chemical Industrials ICI||6|
|9||Keton resin N||Beva 371 (SN)||Lascaux Restauro||10|
|10||Methyl hydroxy ethyl cellulose||Tylose MH300 (SD)||Hoechst||4|
|11||Hydroxypropylcellulose||Klucel G (SD)||Lascaux Restauro||4|
|12||Starch carbamate||(SD)||prepared according to (Sayed, et al 1988)||6|
|Table 1: Polymers and resins used in this study|
Unbleached Egyptian linen fabric was used in this work and its specifications (See Table 2).
|Structure||Colour||Brightness (L)||Nominal Wt.||Thread/cm.||Liner density (Tex.)||% of elongation||Tensile strength|
|Table 2: Specifications of used linen|
Preparation of samples:
The fabric was first washed in sterilised distilled water and dried at ambient temperature. The linen fabric samples were cut into 12 x 2 cm (length x width) warp test specimens. The warp strips were produced by ravelling away yarns on each side forming 1.5cm wide strips with a 2.5mm fringe down each side. These samples were used for tensile strength and elongation test. 5 samples were used for each fungus. Other linen fabric samples were cut into 5 x 5 cm (length x width) specimens to be used for Spectrophotometric measurements and S.E.M. 5 samples were used for each fungus. The samples were soaked in polymer preparations, which were previously prepared according to Abdel-kareem, 2000, and dried at ambient temperature.
7 selected active fungal strains isolated from ancient Egyptian linen textiles were used (Abdel-Kareem, et al, 1997). These selected fungal strains are
Treatment of linen with fungi:
Unconsolidated and consolidated samples were treated with these selected fungal strains by using Agar Plate Test with application of pure strains method (Abdel-Kareem, 2000).
Reflection spectra was recorded for both the front side and behind side samples in the visible range (360-800nm) by a Shimadzu Double Beam UV-2101PC Spectrophotometer Equiped with ISR48 Intergating Sphere, with using barium sulphate as a reference (a white standard). In order to determine the relative rate of colour changes of the bio-deteriorated samples the reflectance values were inserted into a computer program which then calculated the CIELAB colour coordinates for L, a, and b values. Calculation of total colour change (D E) is achieved by the use of the following equations: D E = [(D L)2 + (D a)2 + (D b)2]0.5 (Abdel-Kareem, 2000).
A JSM-400 Scanning Electron Microscope was used to record the changes of surface morphology of consolidated and unconsolidated (control) after fungal treatment.
Tensile strength and elongation:
Tensile strength and elongation of samples were measured by using a testing machine, type Zwick 1445. These tests were done according to the standard PN-88/P-04626. The initial distance of jaws was 50 mm and the testing speed was 25 mm / min, temperature was 23o C, and R.H.65%. The average value of five readings for each test was taken.
Tensile strength of unconsolidated (control) and consolidated linen textile samples before and after treated by fungi are shown (Table 3), as well as, loss of strength of consolidated linen textile samples before and after treated by fungi (Table 4). The data show noticeable decreases in tensile strength among all consolidated samples after fungal deterioration. The results show that percentage of loss of tensile strength of samples treated with most tested polymers, exceeds 70%. It means that the majority of tested polymers are susceptible to fungal deterioration. The data also show that the majority of tested polymers reduce loss of tensile strength of linen textiles treated with these polymers after fungal deterioration. The results prove that % loss of tensile strength of most of the samples treated with tested polymers is lower than % loss of tensile strength of unconsolidated samples (control) after fungal deterioration. It means that the majority of tested polymers retard fungal deterioration of linen but does not prevent it. Or in other wards we can say that the majority of tested polymers improve resistance of linen textiles against fungal deterioration. These results also indicate that the ability of tested polymers to improve the linen against fungal deterioration depends on both the type of polymer and fungal species. However, the results show that there is no polymer retard all tested fungal strains. The results prove that linen samples consolidated by Plexisol P-550, Starch carbamate, and Beva 371 present the lowest loss in tensile strength after deterioration by most of the tested fungal strains, while linen samples consolidated by Mowilith, Calaton CA, Plextol B-500 and Acryloid F-10 present the biggest loss in tensile strength after deterioration by most of the tested fungal strains. These results reveal that Plexisol P-550, Starch carbamate and Beva 371 are the most effective polymers retarding fungal deterioration of linen textiles among tested polymers, while Mowilith, Calaton CA, Plextol B-500 and Acryloid F-10 are the least effective ones.
|Lascaux 360 HV||25.78||9.43||2.89||0.94||0.53||2.17||1.04||2.37|
|Table 3: Tensile strength of linen samples consolidated by polymers and damaged by tested fungi|
|Lascaux 360 HV||11,35||67,57||90,06||98,32||98,18||92,54||96,42||91,85|
|Table 4: Loss % of tensile strength of linen samples consolidated by polymers and damaged by tested fungi|
Total colour difference (D
Values of total colour change (D E) of consolidated and unconsolidated linen samples before and after deterioration by fungi are shown in (Table 5). The results show that there are noticeable changes in all consolidated samples after the fungal deterioration. As it was confirmed by Abdel-Kareem, 1998 that fungal deterioration causes changes in the colour of linen. It indicates that all tested polymers are susceptible to fungal deterioration. But the results also showed that the degree of changes in the colour of samples consolidated by most tested polymers, is lower than changes of unconsolidated samples after fungal deterioration. It confirms that the majority of tested polymers cause reduction in fungal deterioration of linen. This reduction depends on both the type of the polymer and the fungal strain. The colour change (D E) show that no polymer reduces fungal deterioration of linen among all tested polymers. For examples, Starch Carbamate and Plexisol P-550 cause reduction in deterioration of linen by all tested fungal species except Trichoderma viride. Paraloid B72 causes reduction in fungal deterioration of linen by Aspergillus terreus, Alternaria tenuissima, and Penicillium funiculosum, while the same polymer does not cause any reduction in fungal deterioration of linen by Trichoderma viride, Aspergillus nidulans, Chaetomium globosum, and Penicillium asperum. The results also show that colour change of some consolidated samples deteriorated by Trichoderma viride are more than unconsolidated samples deteriorated by the same fungus. It means that some of the tested polymers cause acceleration in fungal deterioration of linen by Trichoderma viride. It also confirms that Trichoderma viride is the most active on linen samples consolidated with most of tested polymers among tested fungi.
|Lascaux 360 HV||Back||7.17||3.97||7.94||1.27||3.09||9.42||20.22||6.35|
|Table 5: Colour difference (D E) of linen consolidated by polymers and damaged by tested fungi|
Results of study the surface morphology of biodeteriorated sampleswere recorded by SEM. They show that all consolidated samples after fungal deterioration showed considerable damages of surface. It means that all the tested polymers are susceptible to fungal deterioration. The results show that the damage of the surface of the biodeteriorated unconsolidated samples (control samples), are more than the damage of the majority of biodeteriorated consolidated samples. It confirms that the majority of tested polymers reduced fungal deterioration of linen. The results show that the degree of reduction in damage of the surface morphology depends on both the type of the polymer and the fungal species. Since it is not possible to present here all SEM photographs, I have chosen the most important ones. Photofigure (1) show the most and the least effective polymers in preservation of tested samples. It is clear that Beva 371, Plexisol P-550, and starch carbamate caused little reduction in fungal deterioration of linen samples in the majority of tested fungi. It is clear that the fungal deterioration of linen samples treated with Calaton CA, Mowilith DM5, and Acryloid F10 is similar to or exceeds fungal deterioration of the unconsolidated samples. It means that Calaton CA, Mowilith DM5, and Acryloid F10 do not cause any retardation in fungal deterioration of linen.
SEM photographs of fungal growth on biodeteriorated surface of unconsolidated samples and consolidated after damaged by tested fungi. A) Control sample (2000X), B,C,D,E,F,G,H) unconsolidated samples after deterioration with B) Aspergillus nidulans (1000X), C) Aspergillus terreus (1000X), D) Penicillium asperum (2000X), E) Alternaria tenuissima (2000X), F) Chaetomium globosum (200X), G) Trichoderma viride (1000X), H) Penicillium funiculosum (1000X). Samples consolidated with Beva 371 after damaged, I) Aspergillus nidulans (2000X), J) Penicillium asperum (2000X), K) Trichoderma viride (2000X). Samples consolidated with Plexisol P-550 after damaged by, L) Aspergillus terreus (2000X), M) Aspergillus nidulans (2000X), N) Trichoderma viride (2000X). Samples consolidated with starch carbamate after damaged by O) Penicillium asperum (2000X), P) Chaetomium globosum (2000X), Q) Penicillium funiculosum (2000X). Samples consolidated with Calaton CA after deterioration with Aspergillus nidulans (2000X). Samples consolidated with Acryloid F10 after deterioration with Alternaria tenuissima (2000X). Samples consolidated with Mowilith DM5 after deterioration with Aspergillus terreus (2000X).
A variety of methods were applied in this study to measure fungal deterioration of consolidated linen textiles. In the field of conservation, a combination of factors such as: change of colour, change of tensile strength, change of surface morphology are of importance to the conservators more than growth the organism on the substrate. Thus the conservator may not care whether an organism resides on the surface of a coating as long as it does not effect on the properties of the object such as: discoloration of the object or a loss in strength of the object. Therefore when we evaluate the ability of the polymer to promote or inhibit fungal deterioration of linen textiles, we should have all properties of linen in mind. The obtained results of the study revealed that most of tested polymers retard fungal deterioration of linen textiles. It may stem from a variety of reasons. Polymers increase the degree of polymerisation of cellulose fibers as these polymers bond between the cellulose chains. The highest degrees of polymerisation of the materials increase resistance of these materials against fungal deterioration. Polymers cover linen textile surface with a thin coating film. This coat film acts as a barrier between the fungi and the linen textiles. In order to the fungi to biodegrade textiles, they have to be in touch with the textile fibers. Therefore only the fungi which able to secrete enzymes able to hydrolysis this coat film will be able to biodegrade the linen textile. However, biodeterioration of polymer depends on both the chemical composition of the polymer and the degree of the polymerisation or length of the polymer chain. Some of tested polymers may also have fungicide components in the composition of the polymer that plays a role in increasing the resistance of the polymer against fungal deterioration.
In accordance with the total measurement results, those polymers or resins that showed the most overall retard to the fungal deterioration of linen were Paraloid B72, Beva 371 and starch carbamate. These results in agreement with previous studies on biodeterioration of resins used in conservation field. Sayed, et al, (1988) showed that Starch carbamate, is one of the most resistant to biological attack. (Koestler and Santoro 1988) confirmed that Paraloid B72 is a moderate resistant for biological attack. The total measurement results indicate that those polymers or resins which showed the least overall retardation to the fungal deterioration of linen were acryloid F-10 and Mowilith. These results in agreement with previous studies on biodeterioration of resins used in conservation field, which showed that Acryloid F-10, was one of the least resistant to biological attack (Kowalik 1980, Koestler and Santoro 1988). This study offers evaluation of the most suitable and effective resins or polymers that can be applied safely and successfully in treating ancient Egyptian linen textiles. The present study does not refer to all requirements should be met but only to the role of these polymers in the fungal deterioration. According to Egyptian archaeological rules (Abdel-Hamid, 1989), polymer or resin used in conservation of archaeological textiles should not accelerate the fungal deterioration on these textiles. The results of the present study show that most of tested polymers or resins do not accelerate but retard fungal deterioration by most of the tested fungi. The results also show that all tested polymers or resins susceptible to fungal deterioration. It means that most of tested polymers can be used in conservation of linen textiles as consolidants but not to protect them against fungal deterioration.
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