Tag Archives: gilding

Graphene-gilded artifacts (or artefacts)

Caption: L: An artist rendering of graphene gilding on Tutankhamun’s middle coffin (original photograph copyright: Griffith Institute, University of Oxford). R: Microscope image of a graphene crystal is shown on the palladium leaf. Although graphene is only a single atom thick, it can be observed in the scanning electron microscope. Here, a small crystal of graphene is shown to observe its edges. The team produces leaves where the graphene fully cover the metal surface. Credit: Original photograph copyright: Griffith Institute, University of Oxford

As icons go, Tutankhamun’s middle coffin ranks highly and it’s a great image to use as an example of what might be accomplished with graphene gilding. From a Sept. 10, 2018 news item on Nanowerk,

Gilding is the process of coating intricate artifacts with precious metals. Ancient Egyptians and Chinese coated their sculptures with thin metal films using gilding—and these golden sculptures have resisted corrosion, wear, and environmental degradation for thousands of years. The middle and outer coffins of Tutankhamun, for instance, are gold leaf gilded, as are many other ancient treasures.

In a new study, Illinois’ Sameh Tawfick, from the Department of Mechanical Science & Engineering (MechSE) and the Beckman Institute, inspired by this ancient process, has added a single layer of carbon atoms, known as graphene, on top of metal leaves—doubling the protective quality of gilding against wear and tear.

A Sept. 10, 2018 University of Illinois news release (also on EurekAlert), which originated the news item, offers more details,

Metal leaves, or foils, offer many advantages as a scalable coating material, including their commercial availability in large rolls and their comparatively low price. By bonding a single layer of graphene to the leaves, Tawfick and his team demonstrated unexpected benefits, including enhanced mechanical resistance. Their work presents exciting opportunities for protective coating applications on large structures like buildings or ship hulls, metal surfaces of consumer electronics, and small precious artifacts or jewelry.

“Adding one more layer of graphene atoms onto the palladium made it twice as resistant to indents than the bare leaves alone,” said Tawfick. “It’s also very attractive from a cost perspective. The amount of graphene needed to cover the gilded structures of the Carbide & Carbon Building in Chicago, for example, would be the size of the head of a pin.”

Additionally, the team developed a new technology to grow high-quality graphene directly on the surface of 150 nanometer-thin palladium leaves—in just 30 seconds. Using a process called chemical vapor deposition, in which the metal leaf is processed in a 1,100°C furnace, the bare palladium leaf acts as a catalyst, allowing the gases to react quickly.

“Chemical vapor deposition of graphene requires a very high temperature, which could melt the leaves or cause them to bead up by a process called solid state dewetting,” said Kaihao Zhang, PhD candidate in MechSE and lead author of the study. “The process we developed deposits the graphene quickly enough to avoid high-temperature degradation, it’s scalable, and it produces graphene of very high quality.”

Here’s a link to and a citation for the paper,

Gilding with Graphene: Rapid Chemical Vapor Deposition Synthesis of Graphene on Thin Metal Leaves by Kaihao Zhang, Charalampos Androulidakis, Mingze Chen, Sameh Tawfick. Advanced Functional Materials DOI: https://doi.org/10.1002/adfm.201804068 First published: 06 September 2018

This paper is behind  a paywall.

Gold at the nanoscale in medieval textiles

It takes a while (i.e., you have to read the abstract for the paper) to get to the nanoscale part of the story. In the meantime, here are the broad brushstrokes (as it were) from a group of researchers in Hungary, from an Oct. 11, 2017 American Chemical Society (ACS) news release (also on EurekAlert),

Gold has long been valued for its luxurious glitter and hue, and threads of the gleaming metal have graced clothing and tapestries for centuries. Determining how artisans accomplished these adornments in the distant past can help scientists restore, preserve and date artifacts, but solutions to these puzzles have been elusive. Now scientists, reporting in ACS’ journal Analytical Chemistry, have revealed that medieval artisans used a gilding technology that has endured for centuries.

Researchers can learn a lot about vanished cultures from objects left behind. But one detail that has escaped understanding has been the manufacturing method of gold-coated silver threads found in textiles from the Middle Ages. Four decades of intensive research yielded some clues, but the findings have been very limited. Study of the materials has been hindered by their extremely small size: A single metal thread is sometimes only as thick as a human hair, and the thickness of its gold coating is a hundredth of that. Tamás G. Weiszburg, Katalin Gherdán and colleagues set out to fill this gap.

Using a suite of lab techniques, the researchers examined medieval gilded silver threads, and silver and gold strips produced during and after the Middle Ages. The items come from European cultures spanning the 13th to 17th centuries. The researchers characterized the chemistry of the silver thread, its gold coating, the interactions between the two and the shape of metal strips’ edges. To characterize the threads and strips, the researchers combined high-resolution scanning electron microscopy, electron back-scattered diffraction with energy-dispersive electron probe microanalysis and other analytical methods. Though previous studies indicated that these tiny objects were manufactured by a mercury-based method in fashion at that time, the new results suggest that the threads were gilded exclusively by using an ancient method that survived for a millennium. The goldsmiths simply heated and hammered the silver sheets and the gold foil together, and then cut them into strips. It was also possible to determine whether scissor- or knife-like tools were used for cutting. The results also show that this process was used widely in the region well into the 17th century.

The authors acknowledge funding from the European Social Fund.

Here’s an image of medieval bling,

Caption: A new study unravels how medieval artisans embellished textiles with gold. Credit: The American Chemical Society

Finally, here’s the abstract with the information about the nanoscale elements (link to paper follows abstract),

Although gilt silver threads were widely used for decorating historical textiles, their manufacturing techniques have been elusive for centuries. Contemporary written sources give only limited, sometimes ambiguous information, and detailed cross-sectional study of the microscale soft noble metal objects has been hindered by sample preparation. In this work, to give a thorough characterization of historical gilt silver threads, nano- and microscale textural, chemical, and structural data on cross sections, prepared by focused ion beam milling, were collected, using various electron-optical methods (high-resolution scanning electron microscopy (SEM), wavelength-dispersive electron probe microanalysis (EPMA), electron backscattered diffraction (EBSD) combined with energy-dispersive electron probe microanalysis (EDX), transmission electron microscopy (TEM) combined with EDX, and micro-Raman spectroscopy. The thickness of the gold coating varied between 70–400 nm [emphasis mine]. Data reveal nano- and microscale metallurgy-related, gilding-related and corrosion-related inhomogeneities in the silver base. These inhomogeneities account for the limitations of surface analysis when tracking gilding methods of historical metal threads, and explain why chemical information has to be connected to 3D texture on submicrometre scale. The geometry and chemical composition (lack of mercury, copper) of the gold/silver interface prove that the ancient gilding technology was diffusion bonding. The observed differences in the copper content of the silver base of the different thread types suggest intentional technological choice. Among the examined textiles of different ages (13th–17th centuries) and provenances narrow technological variation has been found.

Here’s a link to the paper,

Medieval Gilding Technology of Historical Metal Threads Revealed by Electron Optical and Micro-Raman Spectroscopic Study of Focused Ion Beam-Milled Cross Sections by Tamás G. Weiszburg, Katalin Gherdán, Kitti Ratter, Norbert Zajzon, Zsolt Bendő, György Radnóczi, Ágnes Takács, Tamás Váczi, Gábor Varga and György Szakmány. Anal. Chem., Article ASAP DOI: 10.1021/acs.analchem.7b01917 Publication Date (Web): September 19, 2017

Copyright © 2017 American Chemical Society

This paper is behind a paywall.

One final comment, if you read the abstract, you’ll see how many technologies the researchers needed to use to examine the textiles. How did medieval artisans create nanoscale and microscale gilding when they couldn’t see it? I realize there are now some optical microscopes that can provide a view of the nanoscale but presumably those artisans of the Middle Ages did not have access to that kind of equipment. So, how did they create those textiles with the technology of the day?

Better than today’s nanotechnology-enabled coatings: thin film metal coatings from ancient and medieval times

A July 24, 2013 news item on Nanowerk highlights work by Italian researchers on the topic of gilding and thin films (Note: A link has been removed),

Artists and craftsmen more than 2,000 years ago developed thin-film coating technology unrivaled even by today’s standards for producing DVDs, solar cells, electronic devices and other products. Understanding these sophisticated metal-plating techniques from ancient times, described in the ACS journal Accounts of Chemical Research (“Ancient Mercury-Based Plating Methods: Combined Use of Surface Analytical Techniques for the Study of Manufacturing Process and Degradation Phenomena”), could help preserve priceless artistic and other treasures from the past.

The July 24, 2013 American Chemical Society PressPak release, which originated the news item, gives more detail,

Gabriel Maria Ingo and colleagues point out that scientists have made good progress in understanding the chemistry of many ancient artistic and other artifacts — crucial to preserve them for future generations. Big gaps in knowledge remained, however, about how gilders in the Dark Ages and other periods applied such lustrous, impressively uniform films of gold or silver to intricate objects. Ingo’s team set out to apply the newest analytical techniques to uncover the ancients’ artistic secrets.

They discovered that gold- and silversmiths 2,000 years ago developed a variety of techniques, including using mercury like a glue to apply thin films of metals to statues and other objects. Sometimes, the technology was used to apply real gold and silver. It also was used fraudulently, to make cheap metal statues that look like solid gold or silver. The scientists say that their findings confirm “the high level of competence reached by the artists and craftsmen of these ancient periods who produced objects of an artistic quality that could not be bettered in ancient times and has not yet been reached in modern ones.”

Here’s a link to and a citation for the published paper,

Ancient Mercury-Based Plating Methods: Combined Use of Surface Analytical Techniques for the Study of Manufacturing Process and Degradation Phenomena by Gabriel Maria Ingo, Giuseppe Guida, Emma Angelini, Gabriella Di Carlo, Alessio Mezzi, and Giuseppina Padeletti. Acc. Chem. Res., Article ASAP DOI: 10.1021/ar300232e Publication Date (Web): July 5, 2013
Copyright © 2013 American Chemical Society

The paper is behind a paywall but you can access the abstract and this image, which was likely submitted by the researchers,

Image used to illustrate abstract (downloaded from http://pubs.acs.org/doi/abs/10.1021/ar300232e]

Image used to illustrate abstract (downloaded from http://pubs.acs.org/doi/abs/10.1021/ar300232e]