Spectroscopies at E-RIHS lab in Ljubljana

The last laboratory I visited as part of the “Meaningful Materials in the khipu code” project was the Heritage Macromolecular Laboratory: a joint laboratory between the Institute for the Protection for Cultural Heritage of Slovenia (IPCHS) and the University of Ljubljana.

Accessed through IPERION-HS funding, this laboratory is also among the foundational pillars of E-RIHS. Unlike IPERION (which operates as a network, as a consortium) the upcoming E-RIHS will operate as a proper European Research Infrastructure for Heritage Science.

From left to right, top to bottom: Lucrezia Milillo, Marei Hacke, Lea Legan, Klara Retko, Polonca Ropret in front of the entrance of the laboratory, already displaying the E-RIHS plaque

Here, together with the heritage scientist Marei Hacke, we brought khipu samples to refine and expand our understanding of khipu colours through Raman Spectroscopy and Surface-Enhanced Raman Spectroscopy (SERS).

Marei Hacke preparing khipu samples for Raman Spectroscopy

Even though Liquid Chromatography is the most efficient option for knowing which organic dye has been used, it can be time-consuming; while Raman and SERS have a better ratio of sample quantity/successfulness of the analysis compared to chromatography and are quicker. This means that also one tiny hair is sufficient to obtain a spectrum whether it is an organic dye or an inorganic pigment.

Dr Klara Retko is an expert in the optimisation of the Surface-Enhanced Raman Spectroscopy for the characterisation of organic colourants present on cultural heritage objects. For this reason, it was a great opportunity to have her analyse khipu dyes with Raman and SERS.

The Raman analysis of khipu samples was paired with FTIR-spectroscopy performed by Lea Legan in order to cross-check data about dyes. However, FTIR was particularly useful to analyze khipu vegetable fibres whose nature is still obscure. These data will be also cross-checked with light microscopic and SEM imaging of these fibres, in order to shed light on another still obscure constituent of many khipus. FTIR as well requires a minuscule amount of fibre.

Working at the Heritage Macromolecular Laboratory in Ljubljana has been a great opportunity not only to obtain new exciting findings on khipu colours (which are going to be disclosed in a publication later on) but also for me to enhance my understanding of the very process of sampling. Experiencing the very practicalities behind these analyses, made me understand much better the fibre quantities required for different purposes.

Lucrezia organising the khipu samples in the appropriate bags and updating the project’s spreadsheet

As Straight as a dye

Chromatographic analyses in Pisa

A huge section of this project is dedicated to the understanding of dyes in Andean khipus. We know that colour played an essential role in conveying qualitative information in the khipu semiotics. “The problem is that we don’t know ‘how'” you might have imagined.

Yes. But there’s more. The huge problem with colour, as silly as it might sound to point out, it that it fades in time. And it fades according to multiple co-interacting factors (acidity of the soil, humidity, mordanting techniques, light exposure …).

Therefore, if we really want to think about the role of colour in Andean khipus, we first need to understand how they have been coloured.
For this reason, after all the preliminary morphological studies, technical photography evaluations, and XRF mappings, some khipu samples in this project have been selected for chromatographic analyses.

Samples from a khipu after chromatographic extraction

From 10th to 15th July 2022 I was in Pisa at the Science for Cultural Heritage (SCICH) laboratory in the Department of Chemistry. Here I collaborated with Ilaria Degano, Associate Professor in Analytical Chemistry with an expert and unique knowledge of native South American dyes.

Prof Ilaria Degano preparing the samples for HPLC

Liquid chromatography coupled with diode array detector and with high-resolution mass spectrometry (HPLC–DAD, HPLC–HRMS) was performed for characterizing organic dye composition.

This was the first time ever khipu dyes have been analyzed and identified and will be a unique contribution to our current limited understanding of khipu meaningful colours.

The team and I can’t wait to present the first results coming out of this research in the Dyes in History and Archaeology conference!
Check all the details, the program and how to participate here!

Andean khipus Dating INFN

Today, there is an extreme scarcity of knowledge regarding not only “where” khipus are from, but also “when”. We lack the archaeological context of most of them and of 12 hundred khipus recorded so far, only forty-ish have been radiocarbon-dated.

C-14 dating is not self-sufficient in providing answers to khipus’ temporal origin given the very short time-lapse the Inka empire has been ruling for. However, it is still an essential and large contribution to our understanding of khipus if correlated with morphological and archival information.

From June 27 to July 7 2022, as part of the IPERION-HS project, I was a guest in Florence at the Italian National Institute for Nuclear Physics (INFN) section Cultural Heritage Network (CH-Net).

Here, I collaborated with Mariaelena Fedi (head of the AMS C-14 section), Serena Barone and Lucia Liccioli to radiocarbon date five samples of Andean khipus (also part of the wider research project).

All the samples but one had already been prepared in cathodes for being allocated in the Accelerator Mass Spectrometer (AMS) carousel. Fortunately, I could attend and partially participate in the graphitization of the last sample I brought with me to Portsmouth from Gothenburg.

After graphitization, the sample becomes literally a piece of graphite (only the Carbon atoms of what composed the cotton samples are left). The piece of graphite is encapsulated in a cathode made of aluminium ready to be placed in the AMS’s carousel as portrayed below.

The measurements can be really time-consuming even if letting the AMS work day and night. This was a great time to have a tour of the laboratory, to know the projects they are involved in, and to understand more about the very practicalities of C-14 dating.
The C-14 team has been incredibly instructive and communicative in keeping me updated with everything that was going on and also had astounding patience in explaining to me how AMS C-14 works, how they organize data and how to evaluate results.

During this time I was also able to structure a presentation I then gave to the whole INFN CH-Net team on the last day. This was a great opportunity to give back to the team the importance of their contribution within the broader picture of khipu research. Having feedback from an audience of researchers and professors specialized in physics was a great opportunity for me to enhance and expand my communicative skills and my views about the broader khipu research.

Micro-XRF at Historic England, Portsmouth

Three intense and exciting days (20th-22nd June 2022) saw the team of Meaningful materials in the khipu code busy and excited about using the XRF at Historic England as part of the IPERION-HS-funded project.

Hosted by the materials scientist Francesca Gherardi and the wonderful team of Historic England – Archaeology, the visit aimed to map the khipu samples, especially in the search for possible mordants and auxiliaries possibly associated with differently dyed threads.

Marei Hacke (left) and Francesca Gherardi (right) evaluating the XRF map at Historic England
XRF Tornado M4 on the left
Photo CCBY by Lucrezia Milillo

Historic England in Portsmouth possesses a Bruker XRF Tornado M4 which can perform the scan in a vacuum. This allowed us to detect also very light elements – such as Aluminium, which is known for its mordanting properties.

However, khipu samples are extremely tiny and volatile, therefore they had to be covered with a protecting net in order to prevent them to be blown away when the air was pumped back in the vacuum chamber.

Lucrezia Milillo organizing the khipu samples
Photo CCBY by Marei Hacke

Watch this video to see more about our work at Historic England – Archaeology in Portsmouth.