Potential Issues in the Conservation of Bone and Teeth in Maritime Archaeology

Round 1

Reviewer 1 Report

This is a potentially useful guide for "best practice" aimed at marine/maritime archaeologists, field conservators, collections managers and scientists that wish to access skeletal remains for research. However, to be taken seriously by other professionals in the subject areas it needs to be tightened up and made much more rigorous. In some places it appears rushed.

It could do with a good editing also.

1) Their descriptions of the chemistry and structure of bones and teeth needs improving. There are clear differences in the growth and therefore the microstructures of bones (of all types) and teeth. This should be made clearer since it had a direct bearing on how easily different tissues degrade.

2) The authors' description of where organic materials might be found on archaeological sites seems a little parochial. While it might be true in Australia that there is a paucity of organic objects from terrestrial archaeological sites I can assure them that on urban sites in Europe organic finds are problematically common. Please reword this.

3) The author's grasp of chemistry could be clearer. Mechanisms of damage are not well described. e.g. "If allowed to dry without desalination, salts will expand and damage the glaze of a ceramic, and cause damage to glass artefacts." and "Desalination is crucial with all maritime archaeological artefacts. Bone is liable to be damaged if not desalinated, both physically due to expansion of chlorides upon drying, and chemically, from acid formation due to the hygroscopic nature of salts (Jenssen, 1987). I have explained how this happens in the annotated pdf. It is growth of crystals within pore spaces that causes mechanical disruption of pore spaces. Chlorides? Which ones? What about sulphates or nitrates? Please make the language more precise (even if this results in a moderate overrun on the word limit). What is the mechanism for acidification caused by hygroscopic salts? Do the authors mean ferric chlorides? If so they should be precise.

4) Some of the treatments described seem to be largely for aesthetic reasons. Why exactly are iron stains on bone a problem? If they are stable then removing them is going to cause more damage than leaving them. On the other hand, some staining may suggest an underlying problem that may jeopordise the integrity of the finds in the future (e.g. iron sulphides within the pore structures).

5) The sticky issue of consolidants! "Reversible" or not, it is likely that not much more than 50-60% of the solvent can be removed in future. PVAc emulsions do NOT have excellent penetrative properties. If applied to dry bones then they may well flood the larger pores and run into the vascular canals. They will not penetrate the tissues which is where the strengthening is required. If applied to wet bone then flooding the pore spaces is not going to happen. You will be relying on diffusion and the rates of diffusion in bone microarchitecture of droplets ~1 micron diameter is going to be on the order of many hours.

B-72 in acetone will have much higher and faster penetrative power - but for this the bone must be dry. Which leads me to the gaping hole in the whole manuscript.

6) Nowhere do the authors address how the bone gets from the waterlogged state to the dry state. This is the MOST critical part of the process and is not even acknowledged. If bone, ivory, teeth, etc. manage to survive the drying process they are probably (with some notable exceptions) going to be stable and will not require consolidation.

7) The authors are advised to tone down the preachy or didactic statements in their manuscript. "The vast majority of studies on bone and teeth (e.g., Booth and Bruck, 2020; Cartajena 252 et al., 2013; Sjögren et al., 2017), including specimens stored in maritime archaeological collections, present no mention of any pre-analytic or post-analytic checks, performed with the aim to fulfill any quality assurance requirements." The people doing these analyses are neither stupid or naive. I am sure they control for confounding factors in consultation with curators, conservators and museum scientists.

8) On the subject of which ... "If no data are available, a screening analysis is suggested, in the search of physical alterations and/or consolidants. This could be either achieved by CT-Scan and mass spectrometry, both minimally destructive, or by the same analytical technique planned to support the study" Are physical alterations important? What will a CT-scan reveal. The same analytical technique planned to support the study? Explain.

9) There is some confusing sentence constructions that should be looked at, and my personal bete noir capitalisation of analytical techniques when not a proper name.

10) In summary, in view of the wealth of potential information contained within ecofacts, and human remains in particular, then minimum intervention is most definitely the best policy - an expression not used once in the manuscript!

Comments for author File: Comments.pdf

Author Response

Please refer to attached document. Kind Regards. Edda Guareschi

Author Response File: Author Response.pdf

Reviewer 2 Report

This review article presents the diverse conservation and consolidation techniques applied to material recovered from maritime archaeological sites and discusses the damages and alterations to the material caused by these techniques, as well as how they impact analyses to be performed by a variety of scientific disciplines.

It is very well written and makes a convincing argument for the documentation of preservation techniques. This reviewer supports its publication in Heritage, after minor modifications. I would however appreciate the brief discussion of some unaddressed points:

First of all, what can the authors say about the possibility of not collecting materials and leaving them on site until satisfactory techniques are available?

What about the success of DNA analyses? Has any study presented satisfactory results using material recovered from an underwater site?

The second paragraph of the Discussion presents the details of the alterations observed on preserved material but (as also seen in the comments below regarding the introduction) uses vague language regarding isotope analysis (lines 243 and 244). In what way does coating with acrylic resins “interfere” with radiocarbon analysis? The same question holds for DNA analysis; beyond the “[destruction of] potential DNA traces”, by bleach, how do the other techniques impede or render unreliable possible DNA analyses? A word on the implications for the microscopic analysis of fractures would also be welcome in this paragraph.

At the end of the Discussion, the authors propose screening techniques, to be used where no data regarding the preservation process is available. It should be made more explicit that the X-ray screening techniques themselves are not neutral when it comes to molecular data.

Additionally, the authors should address the following minor issues:

Abstract: Is the “(faunal)” qualifier strictly necessary? I see it is used once later in the text but, in both cases, it seems sufficiently self-explanatory.

Page 3, line 134: What do the authors mean by “confuse”? Are the ¹⁴C dates wrong or unobtainable? Concerning DNA analysis, is the issue inhibition, contamination, or the simple presence of exogenous DNA? I would recommend using a more descriptive term than “confuse” here, maybe “inhibit” or “prevent” if that is the case.

Page 5, line 166: I cannot see the “solid arrows” indicating the knife marks, although these marks are quite visible in any case.

Page 5, lines 167 and 168: Same thing, the figures lack indicative symbols, although they are hardly necessary.

Page 5, Figure 2: There, the arrows would help when the figure is submitted.

Author Response

Please refer to the attached document. Kind Regards. Edda Guareschi

Author Response File: Author Response.docx

Reviewer 3 Report

This is a review of conservation in maritime archaeology.

The citation in line 39 should be amended as follows: "material remains of [hu]man[s] and [their] activities on the sea’". Inclusive language is important for understanding, and more accurate.

By the definition stated in the text, maritime archaeology excludes sites that were originally terrestrial, but then became inundated by the sea. However, such sites face some similar conservational problems to maritime sites. Personally, I think either the review shouldn't be focussed on maritime sites, but rather on underwater sites more generally; or a clear distinction between these two types of sites should to be made in the text.

I am also missing differentiation between freshwater and saltwater conditions.

line 107 I'd exchange "appear" to "become", since the appearance itself is less relevant

line 130 somewhere in this paragraph it should be stated that for material that is to be radiocarbon dated or analysed for other isotope ratios, samples should be taken before consolidation.

line 161: Typo: Tooth of an Australian sea lion; also I see no arrow in the picture. The figure description is also missing information on the consolidation methods used for these objects

line 171: I see no arrows, also a typo (solid arrows). I like this figure. It might be good to add more information on the skulls origin.

line 192: the figure descriptions are out of place here

line 211: should read: bones and teeth

line 237: yes, but for collagen extraction this is done on a piece smaller than 2 g, that is first treated with acid, and then gelatinised, so there will be nothing left to look for other evidence on anyway.

line 264-268: I work in this area. The reason that conservation methods are often not mentioned is because for most terrestrial sites, no consolidants were used (particularly in the case of recent excavation), and so if consolidants are not mentioned, that generally means they were (known or assumed to be) not present. I would suggest rewording your text so you make a clear case for also reporting the lack of consolidating methods, if none were used (which is what is currently omitted), in addition to what is written already.

Line 270 For e.g. stable isotope ratio analyses, it makes little sense to use "the same analytical technique planned to support the study" (so IRMS), because this will just spit out a result, without quality control. For carbon dating, d13C and d15N analyses, what we do is look at the %C, %N, and C:N ratios from the elemental analyser (EA) to check if these values are realistic, and also run FTIR (but animal glues are still a problem since they are similar in composition). Additionally, different parts of the same bone/individual can also be analysed - if these give substantially different results, there is a preservation/consolidation issue. It would be good to cite a few papers in this context, there is a lot published.

I enjoyed reading this paper, it was informative and well written. For this journal, this manuscript really exceeded my expectations. I would welcome more detail on conservation methods more generally, but that probably becomes a problem for the manuscripts word count(?).

 

Author Response

Please refer to the attached document. Kind Regards. Edda Guareschi

Author Response File: Author Response.docx

Reviewer 4 Report

The authors have proposed a very interesting review article about problems of conservation for maritime archaeological bones and teeth remains.

I fully agree with them that this information is crucial to know for allowing a good selection of specimens before any forensic, taphonomic, diagenetic analysis of such bones and teeth. It is also necessary for further mineralogical, datations, molecular analyses to know the employed technique of preservation used as well as damages occuring during specimens preparation.

The manuscript is clear, paedagogic, well written and examples well choosen. The references are appropriate and up to date.

This manuscript must be accepted for publication.

 

Author Response

Please refer to the attached document. Kind Regards. Edda Guareschi

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

This is still disappointing but can be remedied in short order.

The authors still do not understand my original comment about minimum intervention. They have added a sentence that includes "keeping any preanalytical intervention to a minimum" with regards future scientific analysis. But my point was also that this is an important principle in ALL branches of conservation and at ALL stages of intervention, regardless of any future analysis. It is a guiding principle in conservation and is generally identified as such in national and international codes of ethics for conservation organisations. That being said, I see that the AICCM Code of Ethics only mentions minimal intervention with regards to restoration and minimum sampling with regards to analysis. Other codes of ethics are more explicit. 

So! Please mention that both full documentation of interventive treatments and minimum intervention are important guiding principles that must be adhered to in all branches of conservation, not just bones.

On the subject of ethics, this is touched on on Line 196 but I think the ethical aspects of handling human remains must be more explicitly acknowledged. That means in the Ethics statement also. There should be an explainer that the authors are reporting previous work and did not handle human remains as part of this work. Please also quote any appropriate Australian legislation covering this code.

I am unhappy about the use of "nested references". Selwyn and Tse are cited for the work on sodium dithionite treatment of bone. In fact Selwyn and Tse are reporting work done by Godfrey et al. 2002. Please sue the original citation.

The sentence on Lines 299-302 should be deleted. It is nonsensical and reflects badly on the authors to anyone who reads it properly. "Moreover, demineralization by acids (e.g., HCl) to investigate bone collagen, or to achieve histological slides, can dissolve bryozoan skeletons and alter evidence of digestion by predators, such as acid corrosion and rounding of the bone edges [90]." The authors are describing destructive analysis of a sub-sample already selected for sacrifice. It is barely credible to worry about bryozoan skeletons when the sample has been solubilised, gelatinised and combusted to CO2.

On the annotated pdf there are highlighted passages with comments. These comments contain either corrections/amendments to highlighted text in inverted commas; or criticisms and comments that need to be addressed.

Comments for author File: Comments.pdf

Author Response

Please also refer to the attached documents (pdf file and word file)

Author Response File: Author Response.pdf