Michael S. Tite

Papers from the Institute of Archaeology

English

MUCC (Crossref)

Archaeological Collections: Invasive Sampling versus Object Integrity

Crossref

1 
Archaeological Collections: Invasive Sampling versus 
Object Integrity 
 
Michael S. Tite 
Professor of Archaeological Science 
Research Laboratory for Archaeology and the History of Art,         
University of Oxford 
 
Introduction 
In considering the question of invasive sampling versus object integrity, I start, and 
have always started, from the premise that archaeological material should be seen as 
a potential source of information rather than something that must remain totally un-
changed after excavation.  Therefore, I definitely favour invasive sampling over the 
preservation of complete object integrity.  However, having said that, there is clearly 
a need for restrictions on the extent of invasive sampling. 
 
When I started to investigate ancient technologies back in the 1960s, the attitude 
among scientists and curators was entirely different.  Scientific examination was still 
something of a novelty.  We were all uncertain as to what useful information could 
be provided by scientific methods.  Both sides approached the archaeological mate-
rial with a sense of adventure – of advancing into the unknown.  With requests for 
samples being relatively rare, curators tended to be very relaxed, and I remember 
being provided with entire sherds from the Near East by one museum.  Of course, 
there were occasional disasters.  For example, there were rumours that a small group 
of silver coins could not be returned to their museum for several years because they 
had been made too radioactive by irradiating with neutrons prior to neutron activa-
tion analysis to determine their compositions. 
 
However, quite correctly, such relaxed attitudes could not continue as the discipline 
of archaeological science expanded, and thus the requests for samples progressively 
increased.  With the development of new scientific techniques, there were more and 
more requests requiring the repeated sampling of the same archaeological objects, 
either to obtain entirely new information or to improve the accuracy of previously 
obtained information.  Curators therefore began to fear that their objects would not 
survive or, at best, end up looking rather like a sieve!  Furthermore, because of the 
need to repeat measurements in order to achieve increased accuracy, curators tended 
to become more sceptical about the value of scientific examination and scientific 
data. 
 
Fortunately, at the same time, scientists involved in the study of archaeological mate-
rials started to become ‘archaeological scientists’.  There were still, as there are now, 
some scientists with a new scientific technique for which they are trying to find a 
problem to solve and which they consider to be ‘god’s gift’ to archaeology if only 
archaeologists were perceptive enough to appreciate it!  However, aided by the es-
tablishment in 1976 of the Science-based Archaeology Committee within the Sci-
Papers from the Institute of Archaeology 13 (2002): 1-5 
FORUM 
2 
ence and Engineering Research Council, the majority of scientists became progres-
sively better integrated into archaeology.  This integration has continued, particularly 
during the 1990s with the creation of lectureship posts in archaeological science in 
most university archaeology departments and the teaching of archaeological science 
in most, if not all, archaeology undergraduate degree courses.  As a result, archaeo-
logical scientists themselves now fully accept the need to take into account the prob-
lems associated with the risk of physical damage to the objects and the potential loss 
of object integrity when requesting and taking samples.  
 
Criteria to be Satisfied Prior to Invasive Sampling 
As a consequence of these developments, there has been considerable dialogue be-
tween curators and archaeological scientists on the sampling of archaeological mate-
rials, and generally agreed criteria for sampling have now been defined.  First, the 
curator must decide whether the archaeological information that will be obtained by 
scientific examination would be of real value, and then whether the scientific method 
being proposed will really provide this archaeological information.  In making the 
latter decision, the curator will need either to consult with an independent archaeo-
logical scientist or to rely on the integrity of the scientist making the application. 
 
If the proposed research can be justified both archaeologically and scientifically, the 
next question is whether the scientific data required can instead be obtained in a non-
invasive way, sampling only being appropriate if there is no alternative non-invasive 
method.  The feasibility of using non-invasive methods depends on the scientific 
data being sought as well as the type of material being studied.  
 
With the development of analytical methods using laser ablation, it is in principle 
possible to undertake both elemental and isotopic analysis of homogeneous materials 
without the removal of a sample.  However, to use laser ablation for fully quantita-
tive analysis, it is necessary to transport the object to the laboratory where the equip-
ment is housed1.  For inhomogeneous materials, such as pottery and stone (other than 
flint or obsidian), it is necessary to remove a sample even for elemental analysis in 
order to ensure that a representative volume is analysed.  Similarly, the use of mi-
croscopy to investigate the microstructure of materials almost always involves the 
removal of a small sample.  The exceptions are when the entire object can be accom-
modated either under an optical microscope or within the scanning electron micro-
scope chamber.  But, even in this case, it will often be necessary to first remove sur-
face weathering or contamination if valid scientific data is to be obtained and, again, 
the object will need to be transported to the laboratory.  
 
When a sample is taken, it is crucial, whenever possible, that after completion of the 
measurements proposed in the application, the sample is returned to the museum, 
which should take responsibility for storing it and for making it available to future 
investigators.  Sample preservation and storage should not present any problems in 
the case of thin or polished sections used for microscopy.  However, samples taken 
by drilling or abrasion for elemental and isotopic analysis are frequently dissolved in 
acid and vaporised during measurement, the principal exception being borate glass 
pellets prepared for X-ray fluorescence analysis. 
 
Forum: Invasive Sampling vs. Object Integrity 
3 
A further factor that needs to be considered is the reputation of the archaeological 
scientist who has made the application.  Have they been active in the particular re-
search field for a reasonable length of time?  Do they have a good record for the pub-
lication of the results of previous scientific examinations, and do these publications 
indicate that the laboratory in which the work is to be done has good quality control 
on its data?  Furthermore, if the museum to which the application is made has previ-
ously provided samples to the same investigator, have they given the museum an 
adequate report of the results obtained, and have the samples been returned?  
 
If all of the above criteria are satisfied, the final decision on whether or not to allow 
sampling must depend, first, on the risk of physical damage to the object during sam-
pling and, second, on the importance attached to any loss in the integrity of the ob-
ject as a result of sampling.  
 
The decision based on risk of physical damage is undoubtedly the easier of the two 
to make.  Thus, much material from archaeological sites is already in a fragmented 
state and can be readily sampled by drilling, abrading or cutting from a broken edge 
using, for example, diamond-impregnated tools.  Similarly, even when archaeologi-
cal objects appear to be complete, many have a damaged region from which samples 
can be easily removed by drilling, abrading or the application of pressure.  Provided 
that such samples are taken with care by someone, such as a conservator, who is ex-
perienced in the handling of museum objects, there is minimal risk of physical dam-
age to the objects during sampling.  Obviously, in taking samples from such objects, 
it is important to avoid, as far as is possible, any loss to their characteristic form or 
decoration.  Furthermore, a full photographic record of the object, before and after 
sampling, should be made.  
 
In the case of genuinely complete objects, it would still normally be possible to re-
move a small sample by drilling or abrasion from a concealed part of the object, such 
as the base of a pottery vessel, without risk of physical damage to the object.  How-
ever, it is certainly preferable to avoid any sampling of complete objects unless abso-
lutely essential, for example, to establish the object’s authenticity.  Instead, one 
should try to sample comparable but damaged objects, whose link with the complete 
object can be confirmed by non-invasive qualitative analysis of the latter. 
 
In deciding on the importance that should be attached to any loss of object integrity 
as a result of invasive sampling for scientific examination, one first needs to consider 
what is meant by object integrity.  The state of any object in a museum is inevitably 
very different from its state when first produced in antiquity.  In addition to any 
changes due to use and reuse of the object in antiquity, there are the changes that 
have occurred during burial as well as those occurring subsequent to excavation as a 
result of both the action of the post-excavation environment and any conservation 
processes to which the object has been subjected.  In consequence, provided that 
there is minimal loss of an object’s characteristic form or decoration, I believe that it 
is legitimate to question whether the removal of a small sample for scientific exami-
nation will have any significant impact on the overall integrity of an object. 
 
Forum: Invasive Sampling vs. Object Integrity 
4 
The Basis for the Curator’s Decision 
Ultimately, the decision on whether or not to sample must rest with the curator, who 
needs to balance the cultural value of the object against the archaeological value of 
the information that could be obtained as a result of invasive sampling for scientific 
examination.  In making their decision, the curator should, wherever possible, con-
sult, first, with an independent archaeological scientist who will at least be able to 
judge the scientific validity of the proposed scientific examination.  Second, consul-
tation with conservators is essential regarding the possible risk of physical damage to 
the object during sampling.  It can also be helpful, on some occasions, for a conser-
vator to be present during, and perhaps assist with, sampling.  However, it is not a 
conservator’s role to pass judgement on either the cultural significance of an object 
or the extent to which it is important to maintain object integrity.  
 
Third, the curator must consider the views of present and future generations of aca-
demics, and of the general public for whom the objects are ultimately being pre-
served.  Since a majority of academics from across the humanities and sciences tend  
to see museum objects as sources of information, one would expect them in general 
to favour invasive sampling over object integrity, provided that the criteria outlined 
above have been strictly met.  The wide range of TV and radio programmes and gen-
eral books on all aspects of archaeology indicate the enthusiasm for the subject 
among the general public.  Therefore, again, one would expect the general public to 
favour invasive sampling provided that it did not involve obvious physical damage to 
the object, and that the results of the scientific examination were presented in a man-
ner that was generally understandable.  However, in the present political climate, 
invasive sampling of material on which any indigenous peoples might have a legiti-
mate claim should not be undertaken without their prior permission. 
 
Additional factors that the curator needs to consider include, first, whether there is 
some more appropriate source of material for scientific examination, other than that 
in their museums, and second, whether scientific research on the objects should be 
deferred until some entirely non-invasive analytical technique has been developed.  
Obvious alternative sources of material for scientific examination are current ar-
chaeological excavations.  However, it is frequently not possible, outside Europe, to 
remove even the small samples required for scientific examination from their coun-
try of origin.  Therefore, the material collected from past excavations outside 
Europe, and now held in museums in Europe and the USA, is often the only material 
available for scientific examination.  In consequence, without access to this material, 
the possibilities for the scientific examination of archaeological material from out-
side Europe will be severely limited, and progress in the archaeological understand-
ing of early technology and trade will be seriously hampered.  
 
Awaiting the development of an all-powerful, non-invasive analytical technique 
again is not a realistic option.  In addition to the consequent delay in the progress of 
archaeological research into early technology and trade, it is doubtful whether a non-
invasive technique that can provide high resolution compositional and microstruc-
tural profiles to depths of several hundred microns below the surface of an object 
will be developed, at least in the foreseeable future.  In addition, much of the impetus 
for the modification of analytical techniques for the specific study of archaeological 
Forum: Invasive Sampling vs. Object Integrity 
5 
material comes from the need for results that go beyond those already obtained with 
established techniques.  Therefore, without a succession of ongoing scientific pro-
jects to stimulate development, it is unlikely that appropriate new techniques would 
emerge.  
 
A final barrier that must be borne in mind is that requests for invasive sampling can 
add significantly to the many demands that already exist on both curators’ and con-
servators’ time.  Thus, the objects for analysis must be collected together, any possi-
ble impact on them must be assessed, and if the application is approved, then time 
must be set aside for the actual sampling.  Conversely, curators should remember 
that scientific examination is itself a very time-consuming activity, and therefore, 
archaeological scientists tend to be as parsimonious as possible in their requests for 
samples. 
 
Conclusions 
Finally, one needs to consider how satisfactory the present situation regarding access 
to samples for scientific examination is in the UK.  Over the past few years, I have 
applied for samples to the Ashmolean Museum, Oxford,  The British Museum and 
the Petrie Collection, UCL.  In each case, I have been asked to complete an applica-
tion form that aimed at ensuring that the criteria for permitting invasive-sampling, 
outlined above, would be met.  So far, my applications have generally been success-
ful, although I have not always been allowed to take samples from the full range of 
objects requested in my application. 
 
In spite of this comparative success in obtaining samples, there is no doubt that it is 
becoming both more difficult and more time-consuming to obtain samples than it 
was, say, 10 years ago.  This partly reflects the ever increasing demands on curators’ 
and conservators’ time in the more bureaucratic world in which we all now work.  
But, I also feel that, at least in some museums, the emphasis put on object integrity is 
unnecessarily restrictive, especially when the requests are for samples from indus-
trial debris surviving in considerable quantity.  It is not clear to me, however, 
whether this increased emphasis on object integrity comes from curators or from 
conservators.  Interestingly, even though (or perhaps because!) the UK has tended to 
be at the forefront of archaeological science, it is now often easier to obtain samples 
for scientific examination from museums in the US and some other European coun-
tries than it is from museums in the UK.  
 
If the current trend in the UK continues, I fear that progress in archaeological re-
search into early technology and trade could be seriously hampered.  Therefore, I 
would urge that the balance between invasive sampling and object integrity is not 
pushed any further in favour of the latter.  In conclusion, let us always remember that 
objects are primarily sources of information and not ‘holy relics’. 
 
Endnote 
1 Recently semi-portable equipment for laser induced breakdown spectroscopy has been developed for the non-invasive 
analysis of archaeological objects by the Foundation for Research and Technology Hellas in Heraklion, Crete. However, 
the analytical data obtained using this technique is only qualitative or, at best, semi-quantitative. Therefore, although 
potentially a very valuable diagnostic tool, this technique is not a substitute for fully quantitative analysis by laser abla-
tion ICP-MS, for which the objects must be brought to the laboratory. 
Forum: Invasive Sampling vs. Object Integrity 


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