[IEEE Proceedings Electrical Overstress/Electrostatic Discharge Symposium - Orlando, FL, USA...

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+ Static Control Technology Preserves Ancient Egyptian Artifacts Arnold Steinman M.S.E.E. Ion Systems Inc., 1005 Parker Street, Berkeley, CA 94710 510-548-3640 tel. 5 10-548-0417fax [email protected] Abstract - Ancient Egyptian artifacts were deteriorating due to the long term effects of their storage in plastic. Attempts to remove the artifacts caused additional damage. The problem was diagnosed to be due to static charge, and a method was developed to safely remove the artifacts. Due to the insulating materials involved, air ionization was used to eliminate the static charge problem. 1 Background In 1899, two Oxford University scholars, Bernard P. Grenfell and Arthur S. Hunt, led an archaeological expedition to Tebtunis, Egypt. The site was located about 100 miles southwest of Cairo, on the west bank of the Nile. The expedition was financed by the late Phoebe Apperson Hearst, a benefactor to the studies of archaeology and anthropology, as well as to the University of California at Berkeley (UCB). Figure 1 pictures the site in Tebtunis. Figure 1. Excavation Site in Tebtunis The city of Tebtunis was one of the centers for the worship of the crocodile fertility god, Sobek. So revered was this god that it was considered a supreme honor for someone to fall into the Nile and be eaten by a crocodile. The researchers found hundreds of crocodile mummies preserved in the sands surrounding the temple sites in Tebtunis. They were so common, that their importance was overlooked at first. Examples of the mummies are shown in Figure 2. Figure 2. Crocodile Mummies The actual purpose of the expedition was to collect writings on papyrus, the ancient world's paper made from a plant that grew in the Nile river marshes. It was hoped that by deciphering the ancient writings, more would be learned about that society of those times. But the mummified crocodiles, thousands of 38.6.1 EOS/ESD SYMPOSIUM 97-298

Transcript of [IEEE Proceedings Electrical Overstress/Electrostatic Discharge Symposium - Orlando, FL, USA...

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+ Static Control Technology Preserves Ancient Egyptian Artifacts

Arnold Steinman M.S.E.E. Ion Systems Inc., 1005 Parker Street, Berkeley, CA 94710

5 10-548-3640 tel. 5 10-548-0417 fax [email protected]

Abstract - Ancient Egyptian artifacts were deteriorating due to the long term effects of their storage in plastic. Attempts to remove the artifacts caused additional damage. The problem was diagnosed to be due to static charge, and a method was developed to safely remove the artifacts. Due to the insulating materials involved, air ionization was used to eliminate the static charge problem. 1

Background In 1899, two Oxford University scholars, Bernard P. Grenfell and Arthur S. Hunt, led an archaeological expedition to Tebtunis, Egypt. The site was located about 100 miles southwest of Cairo, on the west bank of the Nile. The expedition was financed by the late Phoebe Apperson Hearst, a benefactor to the studies of archaeology and anthropology, as well as to the University of California at Berkeley (UCB). Figure 1 pictures the site in Tebtunis.

Figure 1. Excavation Site in Tebtunis

The city of Tebtunis was one of the centers for the worship of the crocodile fertility god, Sobek. So revered was this god that it was considered a supreme honor for someone to fall into the Nile and be eaten by a crocodile. The researchers found hundreds of crocodile mummies preserved in the sands surrounding the temple sites in Tebtunis. They were so common, that their importance was

overlooked at first. Examples of the mummies are shown in Figure 2 .

Figure 2. Crocodile Mummies

The actual purpose of the expedition was to collect writings on papyrus, the ancient world's paper made from a plant that grew in the Nile river marshes. It was hoped that by deciphering the ancient writings, more would be learned about that society of those times. But the mummified crocodiles, thousands of

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them buried in mass grave sites, were occupying most of the excavation workers’ time. One day, in frustration, one of the workers is alleged to have thrown one of the mummies against a nearby rock, breaking it open. Much to the worker’s surprise, the break in the linen outer wrapper of the mummy exposed what the expedition had been seeking all along, papyrus. Workers then checked the hundreds of mummies that they had discarded and found that about two percent of them contained papyrus. It was used both as a wrapper on the outside of the crocodile carcass, and as stuffing inside to preserve the crocodile shape.

Papyrus Documents Over 20,000 papyrus documents and fragments were removed from Egypt for further study by Grenfell and Hunt. Only about 1600 of these documents have been translated and cataloged. Much to the delight of researchers, the documents were not repetitive religious documents. Instead, they were found to be a random sampling of “scrap paper” that gave an insight into the civilization that existed in Egypt between 300 BC and 300 AD. Included were royal proclamations, information about crop outputs, land transactions and other legal documents, even prenuptual agreements. Most of the documents were written in Greek, the common language of the area after it had been conquered by Alexander the Great. A partial list of the documents includes:

0 Register of Official Business. Homer, “Iliad II”, 2nd century BC.

Sophocles, “Inachus” unpublished fragment, 2nd century BC. List of cultivators of royal lands including their rents.

0

0 Circular and Proclamation in 1 18 BC. 0

In 1938 the collection was transferred from England to the the UCB Hearst Museum of Anthropology and Archaeology. Studies continued until the 1960’s, when the last papyrologist left the UCB staff. The collection is now housed in the UCB Bancroft Library which is overseeing a program to share information with other papyrus researchers worldwide via the Internet.

Appointment of officials to a government posts, 119 BC.

Creating the Problem The arrival of the papyrus on the UCB campus corresponded approximately to another historic arrival, plastic. It had been common practice at the time to preserve ancient documents between sheets of glass. Unfortunately UCB sits right over the Hayward fault. an active earthquake fault. There was a concern that in a serious earthquake the glass panels would break and destroy the collection. The arrival of a new plastic, Vinylite, provided a solution for the problem. The papyrus would be protected in clear, flexible sheets of Vinylite sealed on all four sides, allowing it to be studied while providing protection from damage, even in an earthquake. Almost 50 years later, it was obvious that the change in preservation method had its downside. The flexibility of the Vinylite envelope was meant to protect the papyrus from damage. Instead, the flexibility was breaking up the papyrus during handling and creating a fine dust. Much of the dust fell to the bottom of the Vinylite envelope, but a layer of dust stuck to the inside of the envelope made study of the documents difficult. Scanning the documents for transmission on the Internet was not possible in their present condition. Attempts to move the dust without opening the envelope proved futile. The documents were taped to one side of the Vinylite sheets to hold them in position for study. Early attempts to open the envelopes resulted in the fragile papyrus being torn apart. Documents sealed in Vinylite are shown in Figure 3. In an attempt to find a solution to their problem, conservators at the Bancroft Library looked to their closest resource, the faculty at UCB.

High Tech Connection UCB, as many colleges and universites in the San Francisco Bay Area, has an active involvement in training students in high tech manufacturing technologies. Among other activities, UCB operates a Microelectronics Fabrication Facility including a cleanroom for the production of semiconductor devices. As is common throughout the semiconductor industry, static charge control has been used to reduce problems caused by the attraction of particles, or ESD events that damage product and interfere with equipment. * Due to the unavoidable use of insulating materials such oxide- coated silicon, teflon, and quartz, air ionization is an

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important component of the static control program at the UCB Microelectronics facility.

Figure 3. Papyrus sealed in Vinylite When the director of the Microelectronics facility, Dr. Katalin Voros, learned of the papyrus problem, it occurred to her that both the dust collection and the papyrus adhesion might be somehow related to static charge (static cling?). She spoke to Anthony Bliss, Rare Book Librarian at the Bancroft Library, recommending that he contact Ion Systems, the donor of the air ionization system installed in the Microelectronics facility. Ion Systems is located in Berkeley, a short distance from UCB. In his ensuing conversation with Arnold Steinman, Chief Technology Officer of Ion Systems, Mr. Bliss became convinced that there was a good chance that the papyrus problem was caused by static charge.

Verfiying the Problem A few simple measurements can be done to verify that static charge is a possible cause of the problem. An electrostatic fieldmeter is used for the first test. The vinylite envelope is placed briefly in front of an ionizer to assure that any residual charge is neutralized, both inside and outside. The fieldmeter

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verified this neutral condition. The vinylite envelope is then handled by a person who transfers it from hand to hand for about 1 minute and then wipes a portion of the envelope with a clean, soft, cotton cloth. Fieldmeter readings on the outside are now found to be in the -2000 to -5000 voltshnch range due to triboelectrically generated static charge. These readings occur wherever the vinylite has been touched by the person’s hands or wiped with the cloth. The fieldmeter also indicates a field on the inside surface of the envelope, but this was at lower values likely the result of the charge on the outside. In any case, vinylite appears to be a material that is very easily triboelectrically charged. The vinylite envelope is then neutralized again with the ionizer and supported at a 45 degree angle. Papyrus dust removed from one of the document envelopes is sprinkled on the surface of the vinylite. The vinylite is then shaken gently in an attempt to dislodge the papyrus dust. Most of the dust is removed by this process, and what remained is distributed randomly over the surface of the vinylite. The vinylite is then cleaned and neutralized again with the ionizer. This time, however, one half of the sheet is charged triboelectrically by rubbing with the cotton cloth. Fieldmeter readings up to negative 5000 voltshnch are again found. The procedure with the papyrus dust is repeated. In this case substantially more of the particles adhere to the vinylite after shaking, and most adhere to the half of the vinylite sheet that is triboelectrically charged. Figure 4 shows the test and results. At this point it seems likely that at least the dust problem in the envelopes is related to static charge. There is a good chance that the adhesion of the papyrus sheets to the vinylite is also the result of static charge.

Solving the Problem with Ionization The fragility of the papyrus precluded doing any direct experimentation on it. While its resistance was likely to fall in the static dissipative range, making contact with the papyrus to dissipate static charge would have been difficult. Instead, it was decided to treat it as an isolated conductor. The vinylite appeared to be an excellent insulator. Once charged, it held static charge for a long period of time, and placing it on grounded surfaces had little affect. Chemical antistats and high humdity were not useable as static control methods, again due to the fragilty of the papyrus. At this point it was clear that the only reasonable method to use to neutralize the

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charge on the papyrus and vinylite was air ionization. Since the ionizer used the ambient air in the conservation area, it would not present a chemical or moisture hazard to the papyrus.

i papyrus Papyrus Dust

Pattern . .. .. .. .. .. .. .. . . . . . . . . .. .. .. . .. ,. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. . .. .. .. ..

. . .. .. .. .. .. .. .. .. .. .. .. .- .. .. .. . * .. . .* . * .. .. .‘ .’ . . : : :

.. .. .. .‘ . . . . . . . .

Uncharged Charged Side Side

Figure 4. Particles adhere to charged Vinylite

There was a concern about how to discharge the inside of the envelopes so that the papyrus would not be torn apart by adhesion. Ionization will only be effective if it actually reaches the charged surface. There was also a concern that the airflow of the ionizing blower would damage the fragile sheets of papyrus. A technique was developed to prevent these problems. The conservation setup is shown in Figure 5. 1. Carefully cut open the four sides of the envelope.

2. Mount the ionizer 30-40cm (12-16 inches) away from the open end of the envelope and operate it on low fan speed. 3. Neutralize both sides of the outside of the envelope as it is placed on the worksurface. 4. Slowly draw back the top sheet of the envelope allowing the ionized air to get to the interface between the Vinylite and the papyrus. This process should be done slowly enough that it takes several minutes to separate the entire 40cm (1 6 inch) length of the Vinylite. 5 . The papyrus is now left attached to the bottom Vinylite sheet by its special mounting tapes. As it is not possible to remove the tapes without damaging the papyrus, the tapes must be cut wherever the tapes contact the Vinylite. 6. After all the tapes have been cut, place a glass sheet over the papyrus. Reverse the orientation so that the the papyrus is now face down on the glass sheet. Slowly lift the bottom sheet of Vinylite off the papyrus as in step 4.

7. Monitor the interface between the papyrus and vinylite continuously to assure that there is little or

no adhesion. Slow the process as necessary to prevent damage to the papyrus. 8. Once the papyrus has been transferred to a glass panel, preserve and clean both surfaces carefully with the ionizer in operation to allow removal of the accumulated papyrus dust.

Figure 5. Conservation setup with ionizer

Results Conservation of the papyrus fragments is being done with a grant from the National Endowment for the Humanities. Using the ionizing blower donated by Ion Systems, about 400 of the 1600 papyrus documents in Vinylitehave been moved to advanced glass storage systems. These are now available for study by researchers. Now that the writing on the papyrus is no longer obscurred by dust accumulation, part of the grant money will be used to digitize the images of the papyrus and place them on the Internet. Other institutions, including, Columbia, Duke, Princeton, Michigan, Yale, and the Universite Libre de Bruxelles (Belgium) will also be putting their papyrus collections online. Papyrological scholars worldwide will now have the opportunity to view each others’ collections and share information. It seems likely that there are many more situations where historical artifacts have been preserved in insulating materials that ultimately cause their deterioration. This is the case for many old photographs, for example. Static charges may make the removal process from these insulating materials more difficult. There may be more applications where solutions to static charge problems developed for high technology applications, such as air ionization, may find their way into the preservation of the earth’s history.

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References 2. “Developing an Exit Charge Specification for Production Equipment”, Montoya, J.A., Steinman, A., EOS/ESD Symposium Proceedings 1996, ESD Association, 7902 Turin Road, Rome NY 13440.

1. “Treasures Found Inside Ancient Reptile Mummies Under Restoration at UC Berkeley”, File #14465, Office of Public Information, University of California at Berkeley, 10 1 Sproul Hall, Berkeley, CA 94720.

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