Samples of metal threads were prepared, underwent artificial aging, and cleaned using laser applications to define the efficiency of cleaning that gives the best results without affecting the components of the thread, including metal, fibers, or dyes. The present study aimed to investigate and evaluate laser cleaning of the corroded metal embroidery, revealing the chemical composition of the corrosion and prop and evaluating the effects of laser cleaning on the surface of the metal threads. It utilized SEM and LM to provide morphological information about the surface and the cleaning effect. Moreover, SEM-EDX was used to define the elemental composition, and XRD was employed to offer information on the metal. The restoration of cultural heritage depends on defining the devastating changes to the man-made pieces. It compares pre-and post-restoration conditions of the object (e.g. painting, photography, and material analysis), controlling the conditions that are almost irrevocable. An Interval Digital Macro-photography is employed to control the corrosion PS tests for a long period of museum exhibition [ 1].
Metal threads, as a term, refer to thin, yarn-like textile decorations (strips and wires) made of solid metal. They are a metal-coated organic material or the combination of these with natural or man-made fibers [
Corrosion is one of the most common problems causing the degradation of the metal threads and the textile samples. Corrosion crusts are a mixture of a number of corrosion products with impurities from the surroundings. They cause gradual degradation to the thread surface to become brittle and less shiny. Furthermore, they result in changes to the threads and the textile in embroidered ornament parts and fibers [
Corrosion takes place among granule cells and forms an integrated layer of cuprite (Cu2O( to fill in the gaps. It is joined with the migration of copper ions through the preliminary cuprite layer, forming secondary corrosion products, including cuprite, malachite, and basic copper chlorides. The external corrosion layers often include quartz granules resulting from burial precipitates. Moreover, the differences in burial environments result in additional spaces of different compounds, e.g. sulfates and chlorides [
- With oxygen (O2) to form copper (I) oxide (Cu2O), a reddish corrosion layer, and copper (II) oxide (CuO), a black corrosion layer.
- With hydrogen sulfide (H2S) to form copper sulfide (CuS), a black non-protective corrosion layer, which is usually mixed with copper (II) oxide.
- With carbon dioxide (CO2), in the presence of water, to form basic copper (II) salts on the surface: copper (II) carbonates [CuCO3-Cu(OH)2], green malachite, or [2CuCO3-Cu(OH)2, blue azurite).
- With sulphur dioxide (SO2), nitrogen oxides (NO, NO2, etc.) and other air pollutants, in the presence of water, to form green colored basic copper (II) salts (CuSO4∙Cu(OH)2, Cu(NO3)2∙Cu(OH)2, etc.) on the surface.
- With chloride ions (Cl−) to form copper (I) chloride (CuCl), a greyish-white compound. This is the most damaging of the copper corrosion.
Cleaning of a composite textile is one of the most complex processes because the different materials may need safe and precise methods [
tarnished metal threads made of silver, gilt silver, or copper in textiles is a difficult task, as treatments commonly applied to textile and metals are incompatible [
The metal thread samples measuring (15 cm) were prepared. They were copper wires around a cotton yarn in a direction taking (S) shape (see
Metal threads degrade and corrode because of different factors, including high and varied relative humidity, air pollutants, and high temperature [
temperatures, atoms and molecules move faster causing quick chemical reactions and increasing the rate of decay. In other words, chemical decay increases with higher temperature or relative humidity. It is related to the absorbed water in organic materials or thermal expansion of inorganic materials, especially metals where the size and shape changes [
The metal thread samples were divided into three groups. The first, second, and third groups were exposed to aging for a week, two weeks, and three weeks, respectively in a thermal oven {NIS IMI CHM (01)} after being kept intransparent plastic bags. In addition, SO2 at 60˚C—used in instrument calibration, NaCl solution (20%), and O2 were used. The samples were sprayed every two days over the above-mentioned periods. The cotton cloth embroidered with metal threads underwent the same conditions for three weeks.
The experimental copper samples with corrosion layers on the surface underwent the aforementioned deterioration for three weeks.
- First, the experimental samples were displayed before exposure to define the most appropriate and best ways and the typical duration.
- The metal threads were exposed to many laser rays to identify the most appropriate one for application with studying their positive and negative aspects.
- Infrared laser with a wavelength of 1064 nm was used for the copper samples from 5 to 15 minutes [
- Ultraviolet laser with a wavelength of 355 - 266 nm was used from 5 to 15 minutes [
- Q-Switched Nd:YAG laser with a wavelength of 352 nm [
After a week of the accelerated artificial aging, corrosion appeared on the metal threads (see
- Using infrared laser with a wavelength of 1064 nm for the copper samples from 5 to 15 minutes causes somewhat blackness after increasing the temperature of cotton yarns. The high temperature causes a great color change and roast in the case of long periods of exposure [
- Using the ultraviolet laser with a wavelength of 355 - 266 nm from 5 to 15 minutes gave relatively good results. It affected strongly the cotton and dryness and caused the breaking of textile fibers [
- Using the Q-Switched Nd:YAG laser with a wavelength of 352 nm [
JEOL JSM-5500 LV Scanning Electron Microscope (JEOL, Japan) was used in examining the metal threads (see
Identifying the chemical composition of all samples and analyzing corrosion samples were carried out using X-ray fluorescence analysis (XRF), JEOL JSX Element Analyzer with Energy Dispersive X-Ray Fluorescence system (EDXRF).
XRD Unit, Assuit University, Model PW 1710 control unit Philips, Anode Material Cu, 40 K.V, 30 M.A, 2 Cita from 4 to 60 was used to analyze the samples showing their compounds.
Analyzing the copper sample illustrates that it contained Cu (79.89%) and O (20.11%) (see Figures 22-24). After aging and exposure to deterioration factors, it contained Cu (77.58%), O (20.07%), Cl (1.69%), Al (0.28%), Si (0.21%), K (0.12%), and Ca (0.05%) (see
The first sample included a high percentage of CuO (98.364%), but CaO was low (1.637%) (see
XRD analysis showed copper primarily in addition to other copper oxides indicating corrosion because it is a sample of pre aging thread (see
second sample contained copper mainly and cuprite representing a surface corrosion layer after the exposure to environmental and laboratory factors (see
After Aging | Before Aging | Elements | Samples |
---|---|---|---|
77.58 | 79.89 | Cu | 1 |
20.07 | 20.11 | O | |
1.69 | 0.00 | Cl | |
0.28 | 0.00 | Al | |
0.21 | 0.00 | Si | |
0.12 | 0.00 | K | |
0.05 | 0.00 | Ca |
After Leaser Cleaning | Before Leaser Cleaning | Elements | Samples |
---|---|---|---|
78.82 | 77.58 | Cu | 1 |
20.08 | 20.07 | O | |
0.78 | 1.69 | Cl | |
0.00 | 0.28 | Al | |
0.16 | 0.21 | Si | |
0.08 | 0.12 | K | |
0.09 | 0.05 | Ca |
The authors declare no conflicts of interest regarding the publication of this paper.
Shehata, N.A., Marouf, M.A. and Ismail, B.M. (2020) An Experimental Study on Using Laser for Cleaning Metal Threads. Journal of Materials Science and Chemical Engineering, 8, 46-63. https://doi.org/10.4236/msce.2020.84004