Degree Of Discoloration Research Articles

Surface photo-discoloration and degradation of dyed wood veneer exposed to different wavelengths of artificial light

The surface of dyed wood is prone to discoloration when exposed to light irradiation which significantly decreases its decorative effect and shortens its service life. The influence of light wavelength exposure to the surface of dyed wood was investigated to study the effect on discoloration and degradation. Acid Blue V and Acid Red GR dyed wood veneers were subjected to light exposure with different wavelengths from the UV to visible region (254–420nm). Results showed that the surface discoloration of dyed wood was linearly related to lignin concentration and dyes degradation and the consequent transformation of chromophoric groups such as aromatic (CC) and carbonyl (CO) through methoxy reaction. The dyes, lignin and some active constituents were degraded severely, even at short exposures. Acid Blue V dyed wood exhibited greater discoloration than the Acid Red GR treatment. The reflectance and K/S absorption curve showed a hypochromic effect on the dyed wood surface. The dyes and wood chemical structure played a complex and combined role on the selective absorption of different wavelengths of light. The color change rate was apparent with 254nm exposure in the initial stages, but a greater discoloration rate occurred on the samples irradiated at 313 and 340nm than at 254 and 420nm with the time prolonged. The degradation rate and degree of discoloration correlated well with the light energy and wavelength.

In vitro assessment of color changes of clear orthodontic elastomeric module materials after exposure to high-pigment beverages

BackgroundAesthetic elastomeric modules are subject to staining as a result of exposure to foods and beverages that can cause staining. The objective of this study was to assess, in vitro, color changes of clear orthodontic elastomeric module materials exposed to different staining beverages. MethodsSamples of four brands of clear orthodontic elastomeric modules (Morelli, TP Orthodontics, RMO, and GAC) were immersed for 15 minutes, three times weekly, in four beverages that can cause staining: coffee, cola, black tea, and red wine. Between sessions, samples were stored in artificial saliva at 37°C. Color changes were assessed after 4 weeks using the yellowness index (YI) (ASTM International D-6290/E-313-10 standard practices), calculated according to the Comission Internationale de l'Eclairage L*a*b* system with the aid of a spectrophotometer (range 0 to 100, with higher values indicating more yellowness). YI results were analyzed using ANOVA and the Tukey multiple comparisons test. ResultsDifferent degrees of discoloration were observed across the brands, despite the similarity of chemical structures. Coffee caused the most severe color change (mean ± SD YI 56.1 ± 0.79), followed by red wine (38.0 ± 0.78) and black tea (31.9 ± 0.63); these differences were significant. The GAC modules were the least affected by yellowness, whereas Morelli showed the highest degree of discoloration. Conclusion(s)The intake of foods and beverages with a high pigment content can cause discoloration of clear orthodontic elastomeric modules and thus lead to aesthetic complaints. Our findings can help practitioners select the most appropriate brand of elastomeric modules according to the dietary habits of each patient.

2 MeV PROTON IRRADIATION EFFECTS ON ZnO SINGLE CRYSTAL

Melt grown ZnO single crystal was irradiated with varying fluence of 2 MeV proton beam in the range of 1 × 1016 H +/cm2 to 5 × 1017 H +/cm2. The irradiated spots exhibited varying degree of discoloration due to the irradiation indicating surface and volume defects. The surface roughness of the irradiated spots was measured using atomic force microscopy indicating surface modification of the sample. The extent of the damage on the ZnO single crystal from radiation was assessed using Raman spectroscopy. The emergence of the A1( LO ) band at 579 cm-1 pointed to the significant surface alteration in the ZnO crystal due to proton bombardment.

Laboratory Evaluation of the Anti-stain Efficacy of Crude Wood Vinegar for Pinus densiflora

In Korea, Pinus densiflora is one of the most important indigenous tree species in terms of making high-value wood products. Therefore, Korean sawmills exercise extreme caution to prevent fungal discoloration such as that caused by sapstains and molds on the timber. In this study, the effectiveness of using natural crude wood vinegar to inhibit sapstains and molds, especially on Pinus densiflora (Japanese red pine) was examined. Pinus densiflora wood samples were dipped in absolute and diluted wood vinegar at different concentrations (1:1, 2:1, and 3:1; deionized water to wood vinegar dilution ratio) for 3 minutes and immediately air-dried. In addition, volatile wood vinegar was also used in this study to imitate the condition of wood vinegar when exposed to open air. The degree of discoloration was examined and evaluated every 2, 4, 6, and 8 weeks according to the ASTM D4445-91 Standard Method for laboratory test. Crude wood vinegar inhibited sapstains more efficiently than it inhibited molds. Wood vinegar at a 1:1 concentration was found to be the most optimum treatment for inhibiting sapstains for at least 8 weeks.

Characterization of Degradation of Cotton Cellulosic Fibers Through Near Infrared Spectroscopy

Near infrared (NIR) spectroscopy has been found to be one of the most important characterization tools for polymeric materials based on comparatively simple NIR-favorable chemical groups (i.e., C–H, O–H, and N–H). This paper focuses on characterizing degradation of cotton cellulosic fibers in a historical textile—‘Curtain Dress’ in the famous movie Gone With the Wind through NIR spectroscopy, and investigating morphological and molecular changes associated with appearance change such as discolorations in the same cotton textiles. In this study, we did on-site testing on the ‘Curtain Dress’ with the Brimrose Luminar 5030 NIR-analyzer and analyzed the NIR spectroscopy results at eight locations where different degrees of discoloration occurred on the dress. The study identified the wavelength bands according to NIR spectral absorbancies of the typical functional groups in cellulosic fibers such as C–H, C–O and O–H stretches, compared the absorbance intensities at three main wavelengths, and investigated discoloration in different areas via principal component analysis. The combination factor scores of the 1st and 2nd principal components, which accounted for 99.09 % variance of vibrations within various groups in a molecule measured through NIR, reflected effectively morphological changes in the fiber’s molecular structure and degrees of discolorations.

The Effects of Propolis on Discoloration of Teeth

Objective: Propolis is a resinous material produced by honeybees that has recently gained fame as an antimicrobial agent. This study sought to assess the effects of propolis as an intra-canal medicament on tooth discoloration. The effect of its application technique on the degree of discoloration was investigated as well.Methods: This experimental study was conducted on 40 intact anterior human teeth. After access cavity and canal preparation, the teeth were randomly divided into three groups. In group A, propolis was placed inside the canals and pulp chamber. In group B, propolis was used as an intracanal medicament. Group C was considered as the control group and saline solution was injected into the canals. Labial surfaces of all teeth were digitally photographed using a digital camera (Fujifilm at one day, one week, 2 weeks, one month and 2 months time points. Color of teeth was assessed and measured at incisal, middle, and cervical segments using the CIELab system and Photoshop software. Collected data at different time points were statistically analyzed.Results: The overall color change in the two groups of A and B was significantly different from the control group (P<0.001). Significant changes in color were also noticed in follow up sessions in groups A and B (P<0.001). At 2 months, the difference in overall color change between incisal, middle and cervical thirds of teeth in groups A and B was not statistically significant.Conclusion: Based on the obtained results, application of propolis as an intracanal medicament can lead to clinical color changes in tooth crown. Its application technique has no effect on the degree of discoloration.

Effect of Resin Cements for Porcelain Veneers on the Color Stability after Accelerated Ageing

To assess the color stability of different resin cements after accelerated ageing. Four different resin cements were included in the study (1mm thickness). The resin cements were bonded to ceramic disks (0.5mm thickness) built with the VITABLOCS MARK-Ⅱ ceramic (n=7). All of the samples were stored in 37°C distilled water at dark. Then color measurement were determined using spectrophotometric before and after accelerated ageing in a weathering machine with a total energy of 150kJ/m2. Changes in color (ΔE) were obtained using the CIE Lab system coordinates where a ΔE data above 3 was accepted as visible discoloration. The ΔE of Superbond C&amp;B, RelyX ARC, Variolink Veneer and Tetric Flow were 2.24±0.52, 2.47±0.28, 0.62±0.31 and 0.72±0.31 respectively. The Superbond C&amp;B and RelyX ARC achieved significant higher ΔE than the other groups (P0.05). All of the resin cements assessed in this study show varying degrees of discoloration after accelerated ageing. However, the color change are not beyond the clinical aesthetic demand. And the Tetric Flow and Variolink Veneer demonstrate a higher color stability.

한국전통발효음식과 전문가 치아미백을 시행한 자연치의 색조변화와의 관련성

본 연구는 한국전통발효음식과 미백치아의 색조변화와의 관련성을 알아보고자 시행하였으며, 연구방법은 전문가 치아미백을 시행한 자연치아를 한국전통발효음식에 일정기간 침전 후 치과용 측색기를 이용하여 치아색조변화의 정도를 객관적으로 측정하였다. 본 연구에 사용된 치아시편은 30개로 한 치아당 30회 측정되었으며, 전체 측정 횟수는 900회 실시되었다. 측정은 치과용 측색기 ShadeEye NCC<TEX>$^{(R)}$</TEX> Dental Chroma Meter를 사용하였다. 수집된 자료는 PASW 18.0을 사용하여 분석한 결과, 미백 전, 후 명도와 황색채도에서 유의한 차이가 나타났으며(p<0.001), 용액침전 후 명도와 황색채도는 시간에 따라 변화하였다(p<0.001). 침전용액에 따른 색조변화량의 차이를 알아본 결과, 미백 후부터 1주 동안, 2주에서 3주까지의 기간 동안 각 침전용액에 따라 유의한 차이가 나타났다(p=0.001, p<0.001). 한국전통발효음식은 침전기간과 침전용액에 따라 미백치아의 색조변화에 영향이 있음을 알 수 있었다. 하지만 본 연구는 구강 내의 상태 그대로를 재연하지 못하였기에 구강 내 상태, 섭취빈도, 구강위생관리에 따라 차이가 있을 것이다. This study is to examine the relation between Korean fermented food and discoloration on teeth, which have undergone profession tooth whitening. The color change of natural tooth, which has undergone professional tooth whitening, is objectively measured by dental colorimeter after being immersed in Korean fermented food for certain period. The tooth specimens used in this study are 30 pieces and measured 30 times per one tooth, 900 times totally by dental colorimeter ShadeEye NCC<TEX>$^{(R)}$</TEX> Dental Chroma Meter. As a result of analyzing the collected data by using PASW(statistical package) 18.0, the significant difference is found (p<0.001) in lightness and yellowness before and after of professional tooth whitening. The lightness and yellowness after immersion is changed (p<0.001) according to time. As a result of examining the degree of discoloration based on type of fluids, the similar difference is indicated (p=0.001, p<0.001 1,2 and 3 weeks after getting professional tooth whitening. As a result, Korean traditional fermented food influences on discoloration on bleached tooth depended on the duration of immersion and the type of fluids. However, this study failed to represent internal oral condition accurately therefore the results of this study could be altered by the internal oral condition, frequency of consumption of food, and the management oral hygiene.

GEOCHEMICAL CONTROLS ON CARBONATE SHELL TAPHONOMY IN NORTHERN GULF OF MEXICO CONTINENTAL SHELF AND SLOPE SEDIMENTS

Abstract We examine the linkage between the sediment geochemical milieu and the process of carbonate degradation over a wide range of continental shelf and slope sediments using molluscan shells deployed for 13 years by the Shelf and Slope Experimental Taphonomy Initiative (SSETI). Geochemical characterization of the environment of preservation included the breadth of the pore-water carbonate undersaturation window, a depth-integrated carbonate dissolution index, the depth of minimum pore-water saturation, diffusive fluxes of oxygen and calcium, average sulfate and chloride concentration in the upper 5 cm, and the carbonate and organic carbon fractions in the same sedimentary horizon. Taphonomic indices included the maximum degree of dissolution; average dissolution; the incidences of chalkiness, pitting, deep dissolution, and a soft shell surface; the maximum degree of discoloration; the incidences of fading, gray-to-black discoloration, brown discoloration, and orange discoloration; the presence of pyri...

The effect of staining solutions on the color stability of provisional prosthodontic materials

ObjectivesThe aim of this study was to evaluate the effects of staining solutions on the color stability of self-cure provisional resin materials. MethodsThe specimens were prepared for each of three auto-polymerized bis-acryl resin and auto-polymerized methyl methacrylate provisional resin material. The baseline color values were measured with a colorimeter according to the CIE L*a*b* color scale. After the first measurement (T0), specimens were placed in staining solutions (coffee, coca-cola, burn and distilled water for control group) and the other measurements were taken after 24h (T1), 1 week (T2) and 4 weeks (T3). ResultsData were analyze statistically by (a) repeated measures (ANOVA), (b) one and two way ANOVA, and (c) Tukey HSD multiple comparison tests. At the 24h immersion period, the post hoc analysis indicated that AccessCrown-coffee revealed the highest ΔE* values (4.4). At the second immersion period (1 week), Structur2 SC-coffee had the highest ΔE* values compared with other materials (5.4). ConclusionsThe degrees of discoloration were increased with immersion time. The methylmethacrylate resin was more resistant to discoloration than bis-acryl resins. After immersion for 30 days, the coffee solution resulted in unacceptable discoloration for all the tested materials.

Color stability of white mineral trioxide aggregate

This study aims to evaluate the color stability of white mineral trioxide aggregate (WMTA) after irradiation with three different curing lights and with a fluorescent lamp in an oxygen-free environment. Thirty samples of WMTA were divided into four experimental groups (three curing light and one fluorescent lamp) and one negative control group. The samples in the curing light groups were immersed in glycerine and were irradiated for 20, 60, and 120 s with a curing light. The samples in the fluorescent lamp group were immersed in glycerine and left on a laboratory shelf below a fluorescent lamp, whereas the negative control group was irradiated with a curing light without immersion in glycerine. A spectrophotometer was used to determine the color of each specimen before and after each light exposure and after 5 days. Data were analyzed using analysis of variance and Fisher's least significant difference test. All the groups showed discoloration except for the negative control group. At 20, 60, and 120 s, there were no significant differences between the Optilux and Bluephase groups (which were the darkest). The Demi group was the curing light experimental group that showed the lowest degree of discoloration (P = 0.0001). No differences were observed between the fluorescent lamp and the negative control groups. After 5 days, the fluorescent lamp group also showed darkening of the sample surface and there were no significant differences between this group and the other three experimental groups (P > 0.05). WMTA showed dark discoloration after irradiation with a curing light or fluorescent lamp in an oxygen-free environment. WMTA may cause tooth discoloration when it is used in a coronal position.

배초향 추출액을 이용한 염색포의 염색성 및 항균성

As the test results for surface color, dyeing durability, antibiosis of cotton fabrics and silk fabrics dyed with Agastache rugosa extract, the following conclusions were obtained. The surface color of all the dyed fabrics was confirmed mostly as a GY system. As the result of chrominance(<TEX>${\Delta}E_{ab}$</TEX>) measurement, in the case of cotton fabrics the dyed fabrics treated with <TEX>$Al_2(SO_4)_3$</TEX> mordant showed the highest value and in the case of silk fabrics the non-mordant dyed fabrics showed the highest value. The dyeing durability of test fabrics dyed with Agastache rugosa extract are as follows. As the test results of colorfastness to laundry for cotton dyed fabrics, the discoloration degree showed 1st-2nd grade and the contamination degree showed 4th-5th grade. As the test result of colorfastness to dry cleaning for silk dyed fabrics, the contamination degree showed from 1st to 3rd-4th grade. As the test results of colorfastness to acid artificial perspiration, the discoloration degree showed from 1st to 3rd-4th grade and the contamination degree showed from 3rd to 4th-5th grade. As the test results of colorfastness to alkaline artificial perspiration, the discoloration degree showed from 1st to 4th grade and the contamination degree showed from 3rd to 4th-5th grade. The colorfastness to sunlight showed from 1st to 2nd grade. The colorfastness to rubbing showed from 3rd to 4th-5th grade in dry process and from 2nd-3rd to 4th-5th grade in wet process. As the test results of antibiosis, the decrease rate of germs to virus Klebsiella pneumoniae and Staphylococcus aureus showed at least more than 99% after the wash of 10 times. As the test results of antifungal activity to mycete Trichophyton mentagrophytes and Aspergillus niger, the both cotton and silk dyed fabrics didn't gain the significant antifungal effect.

BLEACHING KASUS DISKOLORASI TETRASIKLIN DERAJAT 3: BLEACHING OF THE THIRD DEGREE TETRACYCLINE DISCOLORATION

Tetracycline becomes one of intrinsic factors which causes tooth staining. Discoloration due to tetracycline is divided into 4 degrees of severity. Bleaching can be treated for the 1st or the 2nd degree. The 3rd and the 4th degree can not be treated but must be veneer. The 3rd and 4th degree are indicated by dark tooth color, and a ribbon-like picture showed in labial teeth. A 30 years female patient came to the Dental Clinic, dental examination found teeth color dark grayish yellow (C4 shade guide color) and in the central of labial there was a picture like white banded. Diagnosed of the case was the 3rd degree of discoloration. On the first visit, dental impression was performed for making bleaching tray. On the second visit, there was polished with pumice powder. Carbamide peroxide 10% as bleaching paste was applied to the labial bleaching tray, and inserted for 30 minutes. Once removed then patient gargled with warm water. Patients got instructions to do it at home twice a day for 2 weeks the result showed third. On the third visite the colour of the teeth look brighter, and there were no gingiva irritation and sensitive teeth. Patient was very satisfied. In conclusion, bleaching of the third degree tetracycline discoloration can make the teeth look brighte.

Effect of the Polishing Procedures on Color Stability and Surface Roughness of Composite Resins

Objectives. To evaluate the polishing procedures effect on color stability and surface roughness of composite resins. Methods. Specimens were distributed into 6 groups: G1: Filtek Supreme XT + PoGo; G2: Filtek Supreme XT + Sof-Lex; G3: Filtek Supreme XT + no polishing; G4: Amelogen + PoGo; G5: Amelogen + Sof-Lex.; G6: Amelogen + no polishing. Initial color values were evaluated using the CIELab scale. After polishing, surface roughness was evaluated and the specimens were stored in coffee solution at 37°C for 7 days. The final color measurement and roughness were determined. Results. Sof-Lex resulted in lower staining. Amelogen showed the highest roughness values than Filtek Supreme on baseline and final evaluations regardless of the polishing technique. Filtek Supreme polished with PoGo showed the lowest roughness values. All groups presented discoloration after storage in coffee solution, regardless of the polishing technique. Conclusion. Multiple-step polishing technique provided lower degree of discoloration for both composite resins. The final surface texture is material and technique dependent.

Modification of beech veneers with N-methylol melamine compounds for the production of plywood: natural weathering

Beech (Fagus sylvatica L.) veneers were treated with two formulations based on N-methylol-melamine (NMM): (1) NMM solution (NMM-1, 10% solid content), (2) fatty acid modified NMM dispersions containing paraffin (with an aluminium salt as catalyst, mNMM-2, 5% solid content). Five veneers were glued with a phenol formaldehyde adhesive to produce plywood. The plywood specimens were weathered outdoors over a period of 18 months according to EN 927-3 (2006). The moisture content of the treated plywood was clearly reduced during the exposure as compared to panels from water treated veneers (controls). As a consequence, the treated plywood displayed higher form stability and less cracks and delamination than the control plywood. Coated, NMM-treated plywood panels displayed remarkable lower degrees of discoloration than the coated controls. These differences between the treated, coated and the coated control panels were not so clearly observed in the case of uncoated panels. The treatment with NMM compounds additionally led to reduced surface colonisation by staining fungi on the indirectly weathered reverse sides of the plywood panels.

Influence of Different Wave-Lengths Artificial Light on Surface Discoloration of Dyed Veneer

Dyed Wood is rapidly degraded by short-wavelength UV radiation, and its degree of discoloration correlate well with the wave length. In the paper we test this hypothesis and analyze chemical change of dyed wood surface affected by UV radiation. So that it will be beneficial for further study on synthesis of photo stabilizer. In this research, dyed veneers are irradiated by artificial light using an ultraviolet accelerated weathering device including 5 different wavelengths (UV to visible). CIE (1976) L*a*b* color measuring system is applied to describe the photo-induced discoloration process of dyed veneer. The reflection curves of spectrum and K-M difference spectra show the diverse change of light absorption and reflection. The results reveal that, samples color is great influenced by 313nm and 340nm UV light, the color stability of dye stuffs is rapidly decreased while stimulated by 254nm UV light. The fastness of dyed veneer has a positive relationship with dye stuffs, Acid Red GR dyed veneer just suffer slight yellowing due to the stability of dye, while Acid Blue V dyed veneer fade obviously and get a tendency of reddish.

Resin cement color stability and its influence on the final shade of all-ceramics

Objectives Adhesive resin cements may go through internal discoloration, which may show-through and affect the appearance of translucent all-ceramic restorations. This in vitro study evaluated the amount of resin cement color change and its effect on the final shade of the all-ceramics. Methods Three different resin cements in both light and dual-cure forms were included in the study (Nexus-2/Kerr; Appeal/Ivoclar Vivadent; Calibra/Dentsply). All resin cements contained veneered (IPS Empress Esthetic, ETC1 shade, 20 mm × 1 mm ingot discs) and uncovered groups ( n = 10/group), all luted on white backgrounds (acetalpolyoxymethylene/Delrin ®). Curing was performed according to ISO standards with a calibrated LED curing-light (Flashlite 1401). Samples were stored in 37 °C distilled water at dark. Spectrophotometric baseline color measurements (Color Eye 7000A) were performed from the samples’ top surfaces at 24 h (D65 illuminator). Samples were subjected to 65 h of accelerated ageing (Atlas Ci4000). Further color measurements from the same areas were recorded in CIE L* a* b* coordinates where a Δ E data above 3 was accepted as visible discoloration (OptiviewLite-1.9software). Statistical analysis was performed using a nested random effects model and Tukey's post hoc analysis. Results Light-cure groups showed better color stability in all three resins but only in Appeal resin cement, the dual-cure group discolored significantly more ( p < 0.001). More discoloration was recorded on uncovered cement groups that represented the exposed cement at the margins. There was no visible color change (Δ E > 3) through the ceramic surface on any veneered group. Conclusions All resin cements showed varying degrees of discoloration after accelerated ageing however their actual color change was partially masked by the ceramic. Dual-cure resin cements may affect aesthetics on restoration margins if directly exposed.

An Effective Anti-Discoloration Coating for Copper

This article investigated the effectiveness of a newly developed anti-discoloration method for copper (C1100). The procedure involved diffusion of aluminum into the copper substrate and the subsequent formation of Cu-Al oxide spinels on the surface by a heat treatment. Samples of C1100 with and without surface treatment were subjected to ageing at 250 � C for various length of time up to 40 min in order to promote surface discoloration due to oxidation. In addition, a commercially available anti-discoloration coating (C-107) was applied on testpieces for comparative studies. Tested samples were subjected to spectral colorimeter studies in order to determine the degree of discoloration occurred on the surface; microstructures and phase identifications were examined by SEM and XRD. In conclusions, the newly developed method exhibited potential to protect the surface of C1100, and its performance surpassed that of C-107. [doi:10.2320/matertrans.M2010330]

Tooth Discoloration of Immature Permanent Incisor Associated with Triple Antibiotic Therapy: A Case Report

Introduction A triple antibiotic mixture of ciprofloxacin, metronidazole, and minocycline was used as an intracanal medicament in an attempt to disinfect the root canal system for revascularization of a tooth with a necrotic pulp. However, discoloration developed after applying the triple antibiotic mixture. Methods Six weeks after a triple antibiotic paste had been applied to the root canal of tooth #8 of a 7-year-old girl, the tooth showed a dark discoloration. An in vitro experiment with human extracted teeth was performed to determine which of the 3 antibiotics caused the tooth discoloration. Another experiment was then carried out to examine whether a currently used dentin bonding agent would prevent or reduce such discoloration. The degree of discoloration was assessed by using a colorimeter. Results Among the components of the triple antibiotic paste, only minocycline caused the tooth discoloration. Moreover, the dentin bonding agent reduced the intensity of the discoloration but did not prevent it. Conclusions The possible esthetic problems with the tooth color should be considered when using minocycline as a canal medication.

Study of Air-Induced Paper Discolorations by Infrared Spectroscopy, X-ray Fluorescence, and Scanning Electron Microscopy

Air-induced paper discoloration is described as being different from other discoloration morphologies. It seems to be the result of prolonged exposure to air in a humid and polluted environment without appropriate protecting coverage. In this work, three folios from the same eighteenth century book, presenting three degrees of discoloration and opacity and subjected to different environmental conditions, were examined and compared. Samples were analyzed and compared by three different instrumental techniques, mid-infrared spectroscopy, X-ray fluorescence (XRF), and scanning electron microscopy (SEM). Chemical and physical changes were confirmed from the data collected by these techniques. The absence of the secondary amide band characteristic of proteins in the infrared spectra of the two discolored folios, accompanied by the appearance and increase of white mineral-like deposits visible in the SEM micrographs, support the idea that oxidation reactions occurred and that these two folios were subjected to more severe degradation hazard.