Archive for the ‘Science’ Category

Field Conservation Methods and the Impact on Organic Residue Analysis

April 3rd, 2014

Field Conservation Methods and the Impact on Organic Residue Analysis

 Sophia Carman

            A main goal of field conservation is to prevent further deterioration and to promote long-term preservation of recently excavated artifacts. This is achieved by various techniques designed to clean and stabilize degraded materials. Additionally, field conservators are also able to make suggestions on proper handling and storage of artifacts, focusing on the continued preservation and longevity of artifacts. Consequently, these techniques may not preserve other important information, such as that from organic residues present on the surface or within the matrix of artifacts (Paterakis 1996). It could be considered contradictory to preserve one aspect of an artifact while destroying another. Oudemans and Erhardt (1996) argue that “there may be a difference in the purpose of conservation treatments, usually directed at preservation and consolidation of the physical, structural and optical qualities of an artifact, and treatments for organic residue analysis, primarily directed at the preservation of chemical characteristics of the original material” (104). Therefore, attention needs to be drawn to proper handling, storage, and conservation of archaeological objects, keeping in mind the preservation of all avenues of information that the object may provide.

Image 1

Figure 1: Canaanite amphora sherd from Amarna with visible organic residues on the inner surface. From:


Traditional field conservation techniques can interfere with organic residue sampling and subsequent analysis (Oudemans & Erhardt 1996; Paterakis 1996). Simple techniques to clean ceramics, such as mechanical cleaning with a brush or wet cleaning with water, may remove organic residues from the surface. Other techniques, such as acid cleaning and consolidation, have the potential of destroying the organic residues altogether. In addition, contaminants can skew the results of organic residue analysis or render the organic residue unobtainable. Such contamination can occur at various points in the excavation and conservation process and is usually the result of the improper handling or storage of an object. Factors, such as fingerprints, transportation, plasticizers from plastic bags, inadequate storage environments, and so on, are examples of points during the excavation process where contaminants can be introduced. Therefore, recent advances in the analysis of organic residues have created a need for a re-evaluation of the treatment and care of archaeological ceramics.

Scholars, such as Paterakis (1996) and Oudemans and Erhardt (1996), have made suggestions on proper treatment procedures of archaeological artifacts after excavation, in specific reference to the preservation of organic residues. It is stated that if organic residue analysis is to be conducted on an object, the recommendation for the handling of the vessel is minimum intervention. Such handling was demonstrated by Evershed et al. (1994) in the collection of recently excavated potsherd samples. It is stated, “Sample handling was kept to a minimum to reduce the possibility of contamination from skin lipids, and the samples were not washed or otherwise cleaned prior to storage” (910). Further analysis of these organic residues did not reveal any contaminations due to excavation or conservation.

The concept of minimal intervention will not only add to the preservation of organic residues, but also promote the preservation of the structure of the object itself. As conservators, we must be cautious of over cleaning, conserving or restoring artifacts at a risk of causing more damage than preservation. Once the information stored within an object is obtained and analyzed, other conservation techniques can be applied to the object. In this way, the full spectrum of information and preservation can be achieved.



Evershed, R. P, K. I. Arnot, J. Collister, G. Eglinton, and S. Charters. 1994. Application of Isotope Ratio Monitoring Gas Chromatography-Mass Spectrometry to the Analysis of Organic Residues of Archaeological Origin. Analyst 119:909-914.

Oudemans, Tania F.M., and David Erhardt. 1996. Organic residue analysis in ceramic studies: implications for conservation treatment and collections management. In Archaeological Conservation and Its Consequences. Preprints of the Contributions to the Copenhagen Conference, 26-30 August 1996. Ashok Roy and Perry Smith, eds. Pp. 137-142. London: International Institute for Conservation.

Paterakis, Alice Boccia. 1996. Conservation: Preservation versus analysis? In Archaeological Conservation and Its Consequences. Preprints of the Contributions to the Copenhagen Conference, 26-30 August 1996. Ashok Roy and Perry Smith, eds. Pp. 143-148. London: International Institute for Conservation.

Archaeological Conservation, Research and Experiments, Science , , , ,

How visible should conservation treatments be?

February 12th, 2014

How visible should conservation treatments be?

 Lawrence Houston

Retaining and producing documentation of conservation treatments is considered a fairly recent development when it comes to historical and artistic works.  The prior philosophy of repairs was often to make them so invisible that the original and the repair could not be told apart.  It was thought that the slightest hint of visible treatment would ruin the value of an object and many objects were ill-treated in order to attain this visual effect.  When conservators worked together to develop treatment ethics, one of the aspects of ethical repair that was examined closely was how treatments should be incorporated into the object as a whole.  How can damage repair be undertaken in a manner that neither detracts from the perception of an object, nor attempts to pass itself off as authentic?

One guidepost that conservators set was the ‘six foot/six inch rule.’  Basically put, a repair should be incorporated into the object so that from 6 feet away, the repair blends seamlessly with the object.  The object and its aesthetic experience should be at the forefront of the observer’s attention.  Treatments should not detract from the appreciation of an object.  However, treatments should not be so invisible that the object becomes something that it is not.  Original detail and the work of time and craft should be distinguished readily from the restoration and stabilization work done to care for an object.  Hence the six inch rule, which states that treatments should be apparent on close examination.

Why make the treatments visible at all?  Conservators have the responsibility of ensuring that an object is allowed to speak for itself.  Hiding the treatments entirely creates a false appearance that can mislead or even create forgeries of authentic craft.  Those who access the objects treated have the right to know which parts of an object are original. Likewise, conservators have the obligation to show what is interpolation or which portions are not supported by authorial intent and are merely an assist to stabilization.  Conservators have developed techniques like tratteggio [Italian for sketching] and rigatini [striping] for adding paint to compensate for loss.  Other times, the ‘reading side’ of an object will not show work that is readily visible from the back.  When treatment documentation is lacking or absent, it is often these visual clues that are an important help to guide researchers and conservators in their approach to an object.

Figure 1

Page from a copy of Homer’s Iliad. 1722. 

Aqueous treatment was being contemplated to fix the staining of the page.  Repairs are almost invisible.

Figure 2

Note the undocumented repairs that are easily visible on close inspection.  Should aqueous treatment be attempted with this object, these historical repairs can be accounted for by the conservator and loss of the information can be prevented. These visible repairs are also of note to researchers.  In this case, the repairs indicate a printing error that was caught and likely corrected early in the object’s life. (Raking and transmitted light used in the photos provided to visually highlight the repairs).

Figure 3

Current AIC guidelines require conservators to “not falsely modify the known aesthetic, conceptual, and physical characteristics of the cultural property.”  As conservators we need to ensure that repairs stay in the background and do not drown out the voice of the object.  But we also need to avoid the vanity of creating a truly invisible repair and work to hone our craft in a way that allows the object to speak for itself.



AIC Code of Ethics.  January 21, 2014.

Applebaum, Barbara. Conservation Treatment Methodology. Lexington, ky 2010

Capel, Chris. Conservation Skills: Judgment, Method, and Decision Making. Routledge. ny, ny. 2000

Phillips, David. Exhibiting Authenticity. St Martin’s Press. NY, NY. 1997

Schweidler, Max.  The Restoration of Engravings, Drawings, Books, and Other Works on Paper.  Ed. Roy

Perkinson.  Getty Conservation Institute. Los Angeles. 2006.

Photo credit: Lawrence Houston.  Images from ΟΜΗΡΟΥ ΙΛΙΑΣ. Homeri Ilias: id est, de rebus ad Trojam gestis. Printer J. R. Prostant. 1722.

General Conservation, Science , , ,

Conservation: Using Others Mistakes to Avoid Our Own

February 14th, 2013

Conservation: Using Others Mistakes to Avoid Our Own

Kate Clothier

Conservation involves multiple fields coming together in order to better protect and understand artifacts. A combination of archaeology, chemistry, even biology can all be called upon at the same time by the conservator whilst they are working on the said object. Since conservation efforts require so many different fields of knowledge, the conservator must be aware of what is going on in other fields. By expanding their gaze, information can flow easier and benefit their effort. The information that can be gained from other fields is not limited strictly to data concerning decay or material makeup, but it can also involve ethical questions.

One such question is where to draw the line at examining artifacts. What is meant by this is how much of an object are we willing to remove and potentially destroy in order to gain information.  Conservators must walk a fine line in determining what is acceptable to “sacrifice” for the good of the entire collection. For example, taking a few coins from a collection of over a thousand and then breaking them down (as in removing a section of it or cutting into the coin) to better understand their process of decay. However, once those coins are broken down, they can no longer be part of the collection.  How is it decided what is ok to take away from the collection since it will no longer be available for future use? In conservation the size of the collection and the potential benefits of ‘sacrificing’ the object are weighed out before anything irreversible is done. This helps to ensure that what is lost is not more than what will be gained.

A prime example of the damage that can be done if the cost vs benefit ratio is not properly followed is highlighted in a University of Arizona Environmental department article concerning the Prometheus Bristlecone pine. A geology researcher eager to get results concerning glacial features decided rather than taking a small sample from the Bristlecone pines to gather his information he would cut an entire plant down for more immediate results. Soon after he cut down one of the Bristle cone pines, it was learned that the plant selected was the oldest tree alive, dating nearly 5000 years old (UA Communications, 2013. “Keepers of Prometheus: The World’s Oldest Tree.” University of Arizona Research & Discovery in Environment & Sustainability, Accessed: Web. 5 Feb. 2013). The article explains that the same results could have been gathered from the plant, dubbed Prometheus, if the researcher had followed the approved methods of dendrochronology by taking small samples of the core, which would not have hurt the plant. This would have allowed future researches the chance to monitor and learn more about the plant survival strategy in addition to the plant yielding the needed information for the geologist in his glacial research, but there was no way to undo what had been done.

This same concept can be applied to the conservation world. The conservator must be careful in what they select to break down and examine in an irreversible way. If the object is one of a kind then it cannot be treated in the same manner that something like a large collection of coins would be treated, or else future information can be lost, similar to what happened with the Prometheus Bristlecone pine.  Taking small core samples can yield useful information without damaging the entire collection. It can explain the material makeup of the object, why or why not it is decaying, what type of decay is happening, and what the best method to protect the object would be. Looking into other fields and the mistakes they have made can help emphasize why conservators need to be so diligent and practical in their art. The information and materials they work with is one of a kind.


Ethics and Theory, Science ,