الفهرس 
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Abstract
The present study consists of five chapters:
The first chapter titled on historical background of copper dark patinas technology. So, this chapter started by identification of patina and patination from historical and artistic view which included explanation of meaning of the patina, etymology of patina term, historical notes on patina and patination processes through the ancient times, the middle Ages, the renaissance age, and 18th and 19th century, and industrial age. Then explain the classification of copper patinas from pretty and destructive view and also its advantages. Then explained the historical references of dark copper/bronze patinas in antiquity wither from it’s pronounce, origins and cultural transmission through the Middle East, India, Islamic world, Tibet, and china.
Then elucidate the morphology and mechanisms of copper and bronze corrosion/patinas wither natural or artificial by review different techniques for producing an artificial patination and its functions on bronze statues, with focusing on production of dark patinas. The artificial patination techniques included direct application; vapor coloring, immersion coloring using chemicals, and heat coloring with refer to its chemical results on copper/bronze.
Finally, the chapter elucidate authenticity study of the ancient bronzes based on the patina-alloy system which included the criteria of authentication of patinas on copper-based alloy, a critical review of bronze authentication, propositions for a new approach of bronze authentication wither the relationship between the alloy and patina or between the patina and corrosive environment, and also the factors controlled in, according that gave global methodology for bronze authentication
The second chapter titled on copper/tin-bronze dark patinas formation and structures. So, this chapter reviews the dark copper and tin bronze corrosion and patinas wither oxides or sulfides. Since, we review dark copper oxides corrosion/patinas (cuprite, tenorite, or paramelaconite) from their properties, structure, and formation wither naturally or Intentional (artificially). By similar manner the chapter elucidate the dark copper and tin-bronze sulfides in progress classes of copper sulfides, known copper sulfides, the chemistry of copper sulfides wither in Cu-S System, crystal chemistry and/or phases in the Cu-S System, structure of copper sulfides, and more importantly copper sulfides corrosion products (chalcocite, djurleite, digenite, anilite, covellite, spionkopite, yarrowite) from their properties, structure, and copper sulfides production wither natural or artificial formation.
The third chapter titled on examination and analysis of some ancient dark patinated bronze objects. It essentially aims to identify the microstructure and composition of the black surface layer on our study group. So, this chapter covers different scientific examinations and analysis to study our study group. Cross-section samples from four artifacts (plaques no.JE. 35107V, Tr.2/12/26/13, JE.35107 Z2, JE.35107 AF) was examined using optical metallurgical and scanning electron microscopy in order to clarify the relationship between the patina layer and the body metal and also to identify metal composition, phase distribution, mechanical and physical properties, thermo-mechanical manufacturing technique, determine the defects in metal surfaces and the grain boundaries. Back-scattered electron images greatly helped in determination of the micro_morphology and the elemental distribution wither in the alloy and\or the dark patina. By use EDS mapping analysis of the same areas, we obtained information on elemental distribution through the sample. XRD and FT-IR spectroscopy perform quantitative and qualitative analysis of the black surface chips to identify the crystalline and noncrystalline phases of the organic and inorganic compounds which composed the black surface material. Since, Fourier transform infra-red spectroscopy was used to establish the presence of any organic compounds in the sample. Finally, coupling of all results of analysis techniques allowed us have a complete enough characterization of the black surface material and also its formation techniques, this in order to choose the suitable materials and methods for treatment and conservation this dark patina layer.
Worth mentioning the examinations by metallographic microscope resulted from all cross sections samples illustrate layered structure of the dark patina above the alloy. It is evident also that the dark patina is only a surface layer on the alloy and is not present in the body of bronze alloy, mean there is not any intermediate region/phase between the dark patina layer and the bronze alloy. Addition that, all dark patinas samples of the study group display heterogeneous textures and thickness. Since, it appears under the metallographic microscope as a mixture of different size yellowish-lustrous grains embedded in mutt-black ground. The thickness of dark patina layer ranges between 73.2:125.25 μm. Also, study cross section samples under the SEM/EDX microscope confirm the same result and confirm that all study group objects are consists of leaded tin-bronze alloy, with trace element of iron element ranges from 0.31-0.62 wt%, and no evidence of gold and silver or arsenic elements was found in the alloys. EDX study of all dark patina samples indicated that the elemental composition is consist of a mixture of carbon, copper oxides and sulphides corrosion which contaminated by basic copper chlorides and carbonates. The occurrence of lead globules in the alloy core confirms that the alloys of all study group composed of copper-tin-lead alloy, wherever lead is not fully miscible in the bronze and tends to form small separated globules within copper-tin alloys, since it separates during solidification and generally its distribution are random, with particles size range from a few microns across to large globules of 30-200 µm in diameter.
The fourth chapter titled on imitation study for production artificial dark copper patinas by heating. So, the essential aim of this chapter is finding out the heat technique to produce dark artificial patinas on simulated bronze plaques and then, more importantly, explain what happens physically and chemically on their surfaces when they are applied. Since, the study allowed us, at first, develop a system of study oxidation of metals at high-temperature by the spectrometry analytical methods. Also, the results of our study highlighted on the protective role of the addition of lead and tin elements in the copper in front of the oxidation reaction at high-temperatures. In addition, it presents a model of oxide layers growth which explaining the moderate role of the lead and tin. This study also brought us information and tracks to help understanding the mechanisms of oxide layers growth in moderated temperatures in damp environment for long time, such as which observe in the archaeological objects. This role is different from the one which is generally observed in the alloys of the same type which tend to form an protective oxide layer BxOy. In the copper- tin system, because of the slow growth of the tin oxide which does not allow the development of a protective coating of tin oxide but it develops a mixed oxide layer of cuprous oxide Cu2O and stannic oxide SnO2 who plays a similar role, which namely almost totally protective in the moderate temperatures (T < 400°C). There is establishment of passivity and so on very protective oxide layer in high temperatures which is not more raised with oxides growth on the copper but with growth rates which strongly lowered according to tin concentration in the alloy. Thus the study able to highlight on the existence of two thresholds concerning to the mechanisms of the bronzes oxidation: A threshold in temperature towards 400°C, since below that observe the formation of a passivity oxide layer and beyond that observe a restoring of the oxides growth laws on the copper which is strongly slowed down. This threshold of temperature coincides with the inversion of the importance of the respective distribution coefficients. Since, copper ions in Cu2O and ions oxygenates in CuO as we can see it on the copper but this threshold is for temperature lower than on the copper due to the presence of the tin. Also, observe even for the high temperatures (T >700°C) an increase of the oxide growth kinetics for the bronze which contain 3 % of tin. Over this threshold the adhesion of oxide layers is very improved and the kinetics growth is strongly slowed down.
The fifth chapter titled on treatment and conservation the selected dark–patinated archaeological bronzes. So that, this chapter deals the documentation, cleaning, restoration procedure (if need) and conservation. The cleaning process will be done by using ultrasonic probe (UDS) technique of the selected bronze objects. The aim of this cleaning procedure of the corroded artifacts is to locate and to eliminate harmful corrosion products above, and in order to reveal artifact’s shape and decoration. So, these processes require the ability of locate its former surface, which termed ”original surface” among the corrosion products. Whether this former surface is still kept in place or has moved upwards among the corrosion products from its original position. So, great care is essential in deciding what to do in case of cleaning, because what looks like corrosion might be the original patina, or ancient artificial patina, so it need very carefully applied, which removing would produce irrevocable damage to the object. The procedure results will be discussed as follows:
- Ultrasonic cleaning is time-saving cleaning technique and its parameters controllability seemed very simple compared to other conventional techniques. Dry ultrasonic mechanism (without any use of water) is represent ideal technique in such case; with avoid the prolonged exposure of a surface to the vibrational actions of the scaling tips that may cause some of thermal effects on the cleaned surface.
- UDS procedure showed good results on the cleaned test samples in medium potentials range 4, 4-5 and 3-4, 4-5 and in duration time of 1.0 and 0.5 minute for each 1.0 cm2 of the object, this standard area in our current studywhich is usually preferred.
- With putting in consideration other constant parameters which related to the instrument model, e.g. output and input power, frequency ...etc. It was observed that higher potentials caused increase of chromatic and morphological alterations in the sample surface. However, in the case of lower potentials, little chromatic effect noticeable was observed.
- Beside to some of mechanical degradation or morphological alterations which may occur during cleaning due to the vibrational action. So that, short time breaks taken during the work is necessary to avoid that, and to allow the generated heat of the involved scaling tips to be enough diminished to be ready to complete the cleaning process.
- Ultrasonic Probe Scaler ‘UDS’ technique is considered as innovative tool in cleaning such a vulnerable type of artifact as which has a protective dark patina (which must be preserved). In addition, UDS is proposed technique was not achieved complete removal of all patina surface, but it aimed basically removing just harmful chlorides corrosion products without any discernible alteration in the dark patina surface.
- Anyway, the safety measures and precaution for this cleaning technique should be highly appreciated and followed to keep the operator safe as possible as and help the cleaning process to be effectively accomplished.
- Finally, optimization of cleaning process for this proposed technique should be highly studied further to help a better cleaning degree to be successfully achieved.