The origin and evolution of copper patina colour

Leygraf, Christofer; Chang, Tingru; Herting, Gunilla; Wallinder, Inger Odnevall

doi:10.1016/j.corsci.2019.05.025

Cited by 54 publications

(51 citation statements)

References 45 publications

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“…We assumed that beneath malachite a layer of cuprite, Cu 2 O, is present. Such a layer when formed in atmospheric conditions is fully attained at thickness of 0.8 ± 0.2 µm [1]. We were not able to identify cuprite on the kettle.…”

Section: Discussionmentioning

confidence: 64%

“…Table 3 presents the different compounds that were found present on the examined samples. The characteristic green-blue appearance of the patina layer is due to the color forming Cu(II)-ion in the outer patina layer which needs to be 12 ± 2 µm to fully cover the inner oxide layer [1]. The patina on the kettle was identi ed as malachite, Cu 2 CO 3 (OH) 2 .…”

Section: Discussionmentioning

confidence: 99%

“…The Cu(II) ion acts as a color forming ion, and is part of all compounds in the outer patina layer and as a consequence it is hard to distinguish different compounds by mere observation of the patina color [1]. On the other hand, the patina can be darkened by presence of copper sulphides or lead, lightened by lead carbonate or tin-oxide and reddened by an underlying layer of copper(I)oxide, cuprite [2].…”

Section: Introductionmentioning

confidence: 99%

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Using characterization techniques for determining the history of a 2 millennia old kettle made of bronze alloyed with iron

Kotlar

Matijaković

Desnica

et al. 2020

Preprint

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A bronze kettle dating from the 1st to 2nd Century was found in a riverbed of the Kupa river in Croatia. After excavation it spent another 50 years in a depot of a museum in atmospheric conditions prior to starting the conservation treatment and our studies. A study on the surface layers development was performed to determine the history of the object. This study is a demonstration of how such analysis can be used to reconstruct what the object went through during its life span.It was determined that the kettle is made of low-tin bronze, called mild bronze, with addition of iron, aluminum, calcium and nickel. Using iron for alloying copper is unusual since pure iron is generally not added to bronze, thus the presented case is a rare subject. Presence of cassiterite SnO2 showed that the kettle was used for preparing food on open fire prior to ending up in the river. While being in the riverbed malachite formed on the kettle. After longer exposure to the river Si-oxides and CaCO3 formed on the surface of the kettle, over malachite. It was shown that the kettle probably had a ferrous alloy handle which degraded and disappeared in time. After excavation, the kettle came again in an oxygen-enriched atmosphere and developed additional surface layers over the malachite layer.

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Section: Discussionmentioning

confidence: 64%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Using characterization techniques for determining the history of a 2 millennia old kettle made of bronze alloyed with iron

Kotlar

Matijaković

Desnica

et al. 2020

Preprint

View full text Add to dashboard Cite

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“…In the hydrated substrates, water molecules act as ligands providing free electrons to Cu 2+ ion (from oxygen atom of water), and the blue color is due to the d-d transition for the d9 configuration of Cu(II) [ 44 ]. Since the reduction process to attain copper metal has to be performed prior to incorporating the substrate into the packaging system, the resultant indicator becomes irreversible once the sensor is oxidized and the color change is produced in real time.…”

Section: Resultsmentioning

confidence: 99%

Microencapsulation of Copper(II) Sulfate in Ionically Cross-Linked Chitosan by Spray Drying for the Development of Irreversible Moisture Indicators in Paper Packaging

et al. 2020

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Copper(II) sulfate-loaded chitosan microparticles were herein prepared using ionic cross-linking with sodium tripolyphosphate (STPP) followed by spray drying. The microencapsulation process was optimal using an inlet temperature of 180 °C, a liquid flow-rate of 290 mL/h, an aspiration rate of 90%, and an atomizing gas flow-rate of 667 nL/h. Chitosan particles containing copper(II) sulfate of approximately 4 µm with a shrunken-type morphology were efficiently attained and, thereafter, fixated on a paper substrate either via cross-linking with STPP or using a chitosan hydrogel. The latter method led to the most promising system since it was performed at milder conditions and the original paper quality was preserved. The developed cellulose substrates were reduced and then exposed to different humidity conditions and characterized using colorimetric measurements in order to ascertain their potential as irreversible indicators for moisture detection. The results showed that the papers coated with the copper(II) sulfate-containing chitosan microparticles were successfully able to detect ambient moisture shown by the color changes of the coatings from dark brown to blue, which can be easily seen with the naked eye. Furthermore, the chitosan microparticles yielded no cytotoxicity in an in vitro cell culture experiment. Therefore, the cellulose substrates herein developed hold great promise in paper packaging as on-package colorimetric indicators for monitoring moisture in real time.

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“…At higher heating temperature, the metal begins to burn from complete heat. At the initial stage a dull, almost invisible red, then a very visible red, then the beginning of orange, and then it melts [22,23].…”

Section: Isochronal Heatingmentioning

confidence: 99%

Physical Behaviour of Thermally Affected Bronze and Brass

Kaiser¹,

Kaiser

2020

JMEST

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The physical behavior of thermally affected cast copper, aluminum bronze and brass has been studied by subjecting to heating isochronally for one hour at a range of 600°C. It shows that solid-solution hardening takes place into the Al added bronze and Zn added brass metal. Due to heating Al forms hard and brittle intermetallic of copper aluminates into the bronze metal which responses some age-hardening effects. The electrical conductivity of the metals increases initially through heat treatment due to stress relieving and finally decreases due to formation of intermetallic precipitates. The color of the heated samples are also studied through tristimulus color parameter 'L*', 'a*', and 'b*' values which were analyzed and evaluated in MATLAB software. It is found that incorporation of Al and Zn affects the color of cast Cu. The overall change of color occurs with increasing heating temperature due to chemical changes like oxidization, intermetallic formation, dissolution of phases, precipitation coarsening and recrystallization. Due to change of hardness and microstructural properties of the experimental metals, the sound intensity level also decreases at high heating temperature. A microstructural study confirms that the cast alloys content the different phases of grains and bring about recrystallized status under heating at 500°C for one hour.

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The origin and evolution of copper patina colour

Cited by 54 publications

References 45 publications

Using characterization techniques for determining the history of a 2 millennia old kettle made of bronze alloyed with iron

Using characterization techniques for determining the history of a 2 millennia old kettle made of bronze alloyed with iron

Microencapsulation of Copper(II) Sulfate in Ionically Cross-Linked Chitosan by Spray Drying for the Development of Irreversible Moisture Indicators in Paper Packaging

Physical Behaviour of Thermally Affected Bronze and Brass

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