Report from the lab: analysing stable isotopes in cod bones
Medieval Oslo gradually became part of an international trading network. Written sources indicate that export of cod, hides and furs played an important role in the trade. Interestingly, fish bones make up a relatively small part of the total remains of animal bones from medieval Oslo. Did the rising volume of fish export result in a declining availability of fish in Norwegian towns? Or were Arctic stockfish consistently available in Oslo? Alex Hirons is now analysing fish bones found in the excavation of Oslogate 6 by stable isotopes of carbon, nitrogen, Sulphur and hydrogen. We are trying to find out from where Oslo was securing its fish supply.
Alex promise that there`s a smile behind the mask
Here is Alex, reporting from the lab preparing Batch 2 for demineralisation:
I cleaned the samples with a sand blaster & weighed total cleaned sample.
I then took a sub-sample with a Dremel drill, & placed this into a test tube (all labelled with sample code & weighed the week before).
These tubes are then re-weighed once they contain the sub-sample, & the empty tube is subtracted to find the exact sample weight.
All samples then submerged in 0.5 molar Hydrochloric acid, covered with foil & put in the fridge. This is to remove the mineral component of the bone, leaving behind the collagen we need for isotopic analysis.
These samples are monitored daily; samples that are ready will be soft & malleable. This is checked using a glass pipette to see how rubbery the sample is (I.e., if you press it against the side of the test tube, does it mould itself to the tube or is it still hard/stiff?). The acid is replaced every other day; excess acid is poured or filtered away, & fresh acid is applied. Making new bottles of correctly-diluted acid is another regular lab job!
The samples are now demineralising (80 samples in total). The next step is gelatinisation. Wait and see!
- What can animals tell us? Research questions and preliminary analyses from Oslogate 6 Sep. 14, 2021
- Report from the lab: analysing stable isotopes in cod bones Dec. 21, 2020
- Legumes Oct. 27, 2020
About Food in the Middle Ages
On this blog, we’ll talk about what kind of food people ate in the Norwegian Middle Ages by shining a light on local cultivation and recipes. We will show results from the research laboratories and exciting artifacts from our collections that tell of a diverse food culture, especially in the medieval towns, which consisted of so much more than just meat and porridge.