For the last three weeks CHP’s Olly Davis, with a lot of help from Julia Best, Paul Kemble and other CAER volunteers, has been wet sieving the soil samples taken from Caerau during the summer’s excavations. Read the latest blog to find out what they discovered…and how cold they’ve been!
Paul and Julia start sieving
All the artefacts we recover when we’re digging, such as pottery, animal bones and metalwork, can begin to tell us a story about how people in the past lived. But some material is so small it’s not visible with the naked eye – this may include tiny plant and animal remains which can provide clues to the ancient environment – so we take samples of the soil which we sieve to find those tiny clues about prehistoric lives.
If you visited the dig during the summer you may well have noticed lots of blue bags being filled with soil by eager archaeologists. These were the samples we took – and we took a lot of them!
For three weeks we’ve been based at St Fagans Museum wet sieving all those 100s of bags! Wet sieving is a process where we use water to wash the soil through very fine-mesh sieves. Once all the soil is washed away you end up with two residues.
Nice bit of prehistoric pottery from the coarse residue
The first is a coarse residue that gets caught in the mesh (all the stones, pottery etc). The second is known as the ‘flot’ – this includes all the very small, light, mainly organic remains that float to the surface in the wet sieve tank and we collect in small round sieves. The flot can include small seeds and plant remains which will be able to tell us about the diets of the prehistoric occupants of Caerau Hillfort, as well as charcoal which we’ll be able to use to radiocarbon date the site.
The whole process can take quite some time, mainly depending on what the soil in the samples is like. The soil from Caerau is very clayey so it takes a long time to dissolve away – and that means it requires us archaeologists to have our hands in very cold water for a very long time!
Despite the numb fingers and toes the sieving has been really rewarding. There’s been loads of finds from pottery and iron nails to carbonised grains of barley and wheat – the Iron Age occupants at Caerau Hillfort must have been growing these crops in fields where the houses of Caerau and Ely now sit!
Some of the grains (tiny black dots) that have floated off from the sample
We’ve also recovered lots of small fragments of burnt animal bone – the remains of meals that the prehistoric hillfort residents cooked and ate – and the shells of tiny snails that lived 2000 years ago. The snail shells might sound insignificant, but they’re not at all – in fact they’ll be extremely useful and experts will be able to inform us if they are woodland or open ground species thus telling us if the hilltop was wooded in the past.
All the residues now need to dry before we can examine them more fully, but from what I’ve seen come out of the sieve our story of Caerau Hillfort will now be much richer!
A ‘friend’ on the farm comes to see what we’re up to!