Last updated: July 20, 2023
Article
Podcast 061: The Molecular Weight of Silk and Interpreting “Biscuits”
National Park Service
First NCPTT Summer Intern
Jason Church: Kathryn you have the distinction of being the first summer intern at NCPTT, which we’ve had lots of and we’re doing several interviews with past interns currently and you’re actually the first. So can you tell us a little bit about spent your time at NCPTT?
Kathryn Hallett: Sure, I didn’t realize that I was the first intern so that is quite an honor. My internship was in the summer of 2001, between roughly the beginning of June to the beginning of September. The internship came about because, at the time I was carrying out a master’s program in conservation science in London, and that was at the Royal College of Arts.
Kathryn Hallett: I was doing a placement at The British Museum and my supervisor there was a scientist called Sue Bradley, who was a contact of the materials scientist at NCPTT, Mary Striegel. I was looking for a summer internship as part of my master’s program and Sue suggested that she thought I would get a lot form working with Mary, and I was interested in working abroad.
Kathryn Hallett: I contacted Mary and she very generously accepted my request for an internship and I yes, flew over a very long journey over to Alexandria airport which, for me was quiet an eye opener, tiny airport via Houston. Mary herself came and picked me up and was so very generous with her time and hospitality.
Kathryn Hallett: While I was at NCPTT, the main project I worked on was … well I was working on a small part of a larger research project, to evaluate an awful organic polymer that was proposed for use on limestone. The aim of this polymer coating was to try and reduce sulfur dioxide deposition. It was an ongoing program and a joint research project between NCPTT and DuPont, the chemical company.
Kathryn Hallett: I was working with Mary and with another scientist called Elizabeth Bede, and a further scientist called Deig Sandoval. Together they had put together this project with DuPont, and I was able to go and work for a few months to carry out some of the practical work. I was working with the environmental chamber that had been built in the lab at NCPTT, so I got to know that piece of equipment, which is quite an amazing resource.
Kathryn Hallett: I pretty much was able to take it apart and clean it and put it back together again and all of that sort of thing. Mary and Elizabeth taught me how it worked, what it was for, lots of buttons and switches. Essentially enabling them to expose samples of stone to very carefully controlled and monitored environments. So, things like the wind speed, the concentration to the various pollutant gases, temperature and humidity and all of that sort of thing.
Kathryn Hallett: We would then expose samples of limestone, some of which had been treated with this proposed polymer coating and some of which hadn’t been treated as a control setting. Then following the exposure to sulfur dioxide in the big environmental or chamber, we then extracted any deposited pollutants from the limestone and analyzed them using the ion chromatography equipment, which I think you just had upgraded.
Kathryn Hallett: Then we were looking for, obviously sulfates, dissolved sulfates that might have been deposited on the stone to indicate how effective the polymer coating had been. A fascinating project to be a very small part of.
British Museum & Historic Royal Palaces
Jason Church: After you left your summer at NCPTT, where did you go from there, back to your master’s program?
Kathryn Hallett: Yes, That’s Right. I then went into the final year of my master’s program. It was a three-year master’s program because essentially it was run on a part-time bases. I would be part time at the Royal College of Arts, and part time in the labs at the British Museum, so it’s well over three years.
Kathryn Hallett: My internship at NCPTT was between the second and the third year. Once I got back to London, then I was into my final year at the British Museum and writing up my dissertation, which was on a completely different topic. I was looking at lighting conditions for ethnographic exhibitions, so something quite different.
Kathryn Hallett: Then I completed my master’s in 2002, then I was job hunting and I was really, really fortunate, I managed to find a job pretty much straight away. I then was working for Historic Royal Palaces, where I still am today. I was very fortunate to find employment, from yeah, right from the moment I graduated in 2002.
Jason Church: Tell us a little bit about your job now, with The Royal Palaces.
Kathryn Hallett: When I was first employed, back in 2002, I was taken on, on a research contract. Over here in Europe, we have a funding program that’s run by the European Commission and at the time, in 2002. There was a funding round available for cultural heritage research projects.
Kathryn Hallett: Historical Palaces was a partner in a European research project to study the deterioration of tapestries, so I was taken on as scientific researcher to work specifically on it from size exclusion chromatography to evaluate the molecular weight of silk.
National Park Service
Chromotography & Tapestries
Kathryn Hallett: We were looking to see whether we could use that technique as a marker of damage in silk, to help us to understand how deteriorated were the tapestries in the collection at Hampton Court. There were over seventy historic tapestries at Hampton Court, so it’s a fantastic collection to work on. That was the first three years.
Kathryn Hallett: That project I was using size exclusion chromatography and I really benefited from the experience I had had in Louisiana because although ion chromatography and size exclusion chromatography are different techniques the actual equipment I was using was not so different. Obviously, I was using a different solvent and a different separation method, but in terms of the software, writing programs and how to care for the equipment, there was a lot of similarities so I was able to hit the ground running on that research project, which was very helpful.
Kathryn Hallett: As a result of that research project, we were successful in finding a good analytical method for identifying the level of deterioration in silk for tapestries. We were correlating the molecular weight of silk with the tensile strength, although obviously, the tensile strength tests were done on samples, because as you can imagine it’s very difficult to take the right sort of sample from a historic tapestry that one can then use for tensile strength testing, it just wasn’t going to work.
Kathryn Hallett: So, from the historic tapestry samples, obviously very, very tiny, that we were able to take I could use size exclusion chromatography on those samples, but for the correlation between molecular weight of silk and tensile strength, those experiments were all done on model samples.
Kathryn Hallett: So yes, it was a fantastic project to be involved in, working with a great collection. That was up until 2005, when that project completed, then I was fortunate enough to be taken on a permanent contract as a Conservation Scientist at Hampton Court. I carried on some of the research that we’d started on the tapestries, but I also broadened out the research, really to support all of the conservation functions of the royal palaces.
Kathryn Hallett: The charity is an independent conservation charity that at the time looked after five historic sites in the UK. As well as Hampton Court, the charity is also responsible for Kew Palace, which is in Kew Royal Botanic Gardens, the Tower of London, obviously an iconic historic site, world heritage site, Banqueting House in white, which is home to an amazing original Rubens’ painted ceiling, and also Kensington Palace, which is in Kensington Gardens and is still partly occupied by the royal family.
Kathryn Hallett: From that three year research project, from then being taken on as a permanent member of staff, I was able to widen out the research to underpin all of conservation functions of the department at Historic Royal Palaces. At that point, I started work on other materials, as well as tapestries and in fact also returned to stone conservation for a time. I was involved in a research project looking at preventive conservation Reigate stone, which is a particularly troublesome type of stone we have her in the UK.
Kathryn Hallett: It’s a kind of sandy limestone or a limey sandstone, depending on who you talk to, incredibly porous and incredibly soft. Large parts of the Tower of London and Hampton Court are built from Reigate stone and it causes us to have a big problem in terms of its preservation. It was great to be able to draw on some of the knowledge I’d learned with Mary Striegel and other colleagues at NCPTT about stone conservation to work on that project too.
Jason Church: That’s fantastic we would have never known the connection between the two.
Kathryn Hallett: I know. Yeah, all of the research I was involved in, in Louisiana really helped me in many ways, not just learning about how to conduct a rigorous and large scale research project, but small things like, as I said, how to operate chromatography equipment, information about the chemistry and morphology of limestone’s. I’ve drawn so much on what I’ve learned from Mary and her other colleagues; it supported me very much in my career at Historic Royal Palaces.
Jason Church: That’s very encouraging, thank you. Any funny or interesting stories about your time here in Natchitoches?
Kathryn Hallett: Oh well, quite a few I guess, I’ve been racking my brains to try and think of some funny stories, and I’ve thought of quite a few actually. I guess, one of the first things that I noticed when I was in Natchitoches was the cultural differences between that town, and obviously I was use to London, but it gave rise to quite a few humorous situations for me.
Kathryn Hallett: One example, I was staying in university accommodation for part of my internship and there was a supermarket quite a short distance away really, so I would obviously regularly go and visit the supermarket to stock up on my food. I didn’t have a car while I was in Louisiana, I didn’t really see the need for it, Natchitoches is quite a small town as you know.
Kathryn Hallett: I didn’t really expect to travel far, so I didn’t drive a car, but I found that that made me quite an oddity. When I would walk from my accommodation to the supermarket, a couple of times I had people pulling over an asking if I was all right because they were so unused to seeing people walking along the road.
Kathryn Hallett: Whereas, of course, in London it’s the opposite really and people are very accustom to walking from a, to b, but I found that in Natchitoches that made me quite an unusual being. Especially when I was walking along the road in the August heat carrying my shopping bags and all of the kind folks in Natchitoches would think I was probably quite odd and pull over with their cars and see if they could help and give me a ride.
Jason Church: Yes, we’re not much of a walking town, for some odd reason.
Hampton Court, Historic Royal Palaces
Kathryn Hallet: No, which yeah, I found funny. Let me think, What else? Well as I said, Mary Striegel and the other colleagues I worked with, Elizabeth Bede and Deig Sandoval particularly, were so very kind to me, and the hospitality they showed me was amazing. They were always inviting me out for lunch and dinner, and showing me round and introducing me to people, so I really felt part of the community.
Kathryn Hallett: One of the fun events they invited me to, and I don’t remember the name, but it was a festival, it was held at the university, in I guess one of the sports halls, it was over a weekend I think. During the festival I got the chance to try out some unusual cuisine, gator on a stick I had never had before and was quite unwilling to try, but I did give it a go. Everyone said, “Oh, it tastes like chicken,” wasn’t sure about that, but I gave it a go.
Kathryn Hallett: I also got to soak up some of their fantastic blue grass music, have some daiquiris I remember was a big, lots of daiquiris, and enjoy the atmosphere there. That was fun. We had a great social life and everybody was so kind. I remember visiting a colleagues house for a crochet evening with lots of daiquiris. That was fun too. As well as all of the hard work that we did, I really enjoyed meeting everybody at the center and everyone was really kind in helping me feel at home.
Jason Church: Fantastic. You must have gone to Louisiana Folk Life festival.
Kathryn Hallett: Yes, that sounds about right, yeah.
Jason Church: Still a very standard festival for all of our interns to attend.
Kathryn Hallett: Oh good. It was a great experience and great chance to immense myself in Louisiana culture and have some of their Cajun cooking, yes all of that really. The cultural side of the internship, I enjoyed very much indeed. I remember being quite stunned about biscuits because in London or in the UK, a biscuit is something sweet that you have with your cup of tea, but something quite entirely different in the south of America. I enjoyed finding out about that to my surprise as well, that it wasn’t quite the biscuit I expected.
Projects: Terra Cotta Roundels, Gate Houses, Hampton Court
Jason Church: Well any projects that you have coming up that you want to mention to us, anything you have coming up in your current …
Kathryn Hallett: At the moment, I’m working on a project to look at a Terra Cotta conservation. Again, as I mentioned, in my current roll I really focus on whatever material is required for the sort of conservation projects that we have coming up. So I can be working on any material from textile to arms and armor to gilded furniture, and so on and so forth, all of the contents of a royal palace.
Kathryn Hallett: At the moment, my main research project is looking at a set of Terra Cotta roundels that are mounted on the gate houses of Hampton Court. They’re a fantastic survivor; they actually were commissioned by Cardinal Wolsey who was one of Henry the IIX advisors in 1521. There are eleven of these Terra Cotta roundels, they depict Roman Emperors we believe, and they’re still mounted outside on the gatehouse at Hampton Court.
Kathryn Hallett: We have been involved in a research project now since, gosh, probably 2008 to study the materials of these Terra Cotta sculptures to understand there manufacture original decoration because we know from the accounts at the time that they were originally painted and gilded, although they don’t appear that way now, to look at how they deteriorated.
Kathryn Hallett: Some of them are in really good condition and others are in less good condition and then obviously to look at options for their conservation in the future. This research project has involved really every facet of conservation science, everything from looking at the geological provenance of the clay, we’ve been involved in ICP-MS trace element analysis to try and identify the geological provenance of the clay, that we believe is a local London clay.
Kathryn Hallett: I should say we know that the sculptor was Giovanni da Maiano, who was a famous Florentine sculptor, who worked at the court of Henry the IIX. We were looking at the geological provenance of the clay, so whether he brought his clay with him from Florence or whether he used a locally available clay. We’ve also been looking at thermoluminescence dating, because we know that all of the sculptures have been moved and have been restored in one way or another over time.
Kathryn Hallett: We wanted to try and find out which where the original pieces and which are native additions. We’ve also been carrying out pigment analysis and using mammon microscopy, as I mentioned, to try and look at the decoration that might be remaining. We haven’t found very much, but in certain crevices and behind ears and noses of these Roman Emperor sculptures, we have found some traces of polychromy.
Conservation Options
Kathryn Hallett: The second phase of the project has been looking at conservation options, so we’ve been trialing laser cleaning, for example, so that has been really successful. Removing black soiling from Terra Cotta is quite a challenge, because don’t have the same ease of color difference between the soiling and perhaps a paler substance like a paler stone, but we’ve been getting really good results with very little discoloration. That’s been very successful.
Kathryn Hallett: We’ve also been looking at options for consolidation and various water repair compositions. We’ve been looking at different samples of mortars, different mortar mixes, different levels of hydrochloric lime components and we’ve actually been making samples and weathering them up on the roof of Hampton Court to help us decide which recipe of mortar is the right one to use. So, which one is going to weather well and be robust, but not so strong that it risks damage to the Terra Cotta itself. So really all encompassing holistic observation project that I’m really enjoying being part of.
Jason Church: Oh that sounds fascinating, maybe we’ll get to talk to you in the future, when you make some decisions on the sculptures, what decisions you made and why.
Kathryn Hallett: Yes, that would be great. The project is nearing its completion now so we’re starting to look up publishing. We published a paper in the ICOM-CC conference that was in New Delhi a few years ago. We published a paper there about our project and what we were looking at, obviously we’ve moved on since then and we’re now pretty much finishing off our ideas about the treatment phase. So yes, absolutely I’d be happy to talk to you about it another time.
Jason Church: Kathryn, thank you so much for talking to us, we’re glad to have caught up with you and to hear what our first intern has done in your time since here at NCPTT. We really appreciate it, we hope to talk with you again in the future.
Kathryn Hallett: Great, thanks Jason it’s been really great to catch up and relive my wonderful memories from Louisiana.
Read other Preservation Technology Podcast articles or learn more about the National Center for Preservation Technology and Training.