Sieving & Flotation
We had a fairly early start, as we had to get up to ArkT before 9:00 to help Jane, Jo and David load up the van with all the soil samples to take to Oxford Archaeology, so we could start to separate the soil from the interesting stuff(basically what’s left – this will be looked at more closely, under low magnification using a microscope, by an expert). We had 41 boxes and three bags of samples stored at ArkT, and a further 12 boxes which we picked up which Jane was storing at her place – I think that quite a few of us involved in the project are coming to terms with having boxes of finds and assorted archaeological paraphernalia littered around our homes!
Then off to Oxford Archaeology, who have kindly let us use some of their facilities to process our finds – not only the Bartlemas soil samples, but also the Test Pit samples. We generally take soil samples for two reasons; to get an idea about all the very small stuff (2 to 10mm) which would be too finicky to pick out by hand, and to take an environmental sample, where we are interested in the organic stuff – small animal remains (snails, insects, etc) and plant remains (seeds, grain, pollen) which can enable us to build up a picture of the environment at that period.
We are really lucky that Oxford Archaeology (OA) have given us this opportunity; we do have some of the equipment required (though not as many units – at OA we can have more than one team at work at the same time). But apart from the obvious advantage of gaining some priceless training from an expert, 52+ plus boxes of soil samples, taken from fairly clayey soil, generates an enormous amount of spoil a.k.a mud. Not the sort of thing one wants to dump on the doorstep, so to speak, of the guys at ArkT, who are being so helpful to us. It’s the sort of detail which can pull a Community project up short, but which a professional organization can take in its stride.
When we arrived we were greeted by Rebecca Nicholson (OA’s Environmental Archaeology Manager) who shepherded us through a seemingly incomprehensible maze to the wet room, where we would do the work, and introduced us to Julia Meen (their Environmental Archaeologist), who would take care of us for the day. Then we all helped to unload the van and stack up all the boxes ready for the work ahead.
After getting suitably kitted out – wellies and waterproofs being the order of the day; there is a lot of water involved – we got started. We kicked of with sieving the sample which had been taken from one of the skeletons that had been found in trench 2. As it was articulated (all the bones still in the same position as when they had originally been buried) we could not lift it – as the ground around the chapel was consecrated we respected all burials, but as soon as we realized that we had found a burial, we collected all the soil in the cut formed by the burial, so that we would not lose anything. It is surprisingly easy to miss stuff when you’re dealing with, as I mentioned, rather clayey soil. So, after estimating how much soil we had (as I might have mentioned before, everything gets recorded; it was about 15 litres) it got emptied onto the topmost of three sieves – the top one being 6mm (I think), the next one being 4mm and the bottom one 2mm. Armed with a water spray-gun, we took turns washing the soil off the solid residue so that anything smaller than 6mm falls through the sieve to the next layer. After we had all the mud off what was left in the sieve, it gets transferred to a paper-lined tray (appropriately labelled; it’s amazing how many waterproof labels & pens we get through). We then repeat this procedure for the other two trays – I was surprised how much clay gets retained by the lowest, the 2 mm, sieve; with all the water we had poured over the stuff, you would have thought it would have been totally clean by then, but no – it still needed a whole lot of work.
Then took a break for lunch; Gill & I had forgotten to bring sandwiches (well, a bit of a communication breakdown, really) but Gill went round the corner to the recommended deli (Eggs Eggcetera on Botley Road – gets our thumbs up) and took up the whole of the dinner area, rather embarrassingly – though we only realized this after the event. Then got back and chatted to Julia about how many sample boxes she normally gets through in a day – 16! Had a look at the 4 that we were going to do and went outside to look at the heap of boxes outside – a rather depressing sight – it certainly didn’t seem to have got any smaller!
I carried on sieving, with renewed vigour, while Julia explained the other technique, flotation. This involves a large tank with a sieve above it – you wash your sample as normal and all the washed out stuff falls through, though this time you have a very fine mesh membrane forming a ‘basket’ in the tank which catches all the residue from the sieve. Once you have cleaned up the large finds remaining in the top sieve and tagged and trayed it, the second part of the operation starts. Water is pumped into the tank from below so it fills up and overflows over a weir and into a second sieve (the ‘flot sieve’) , while the residue in the mesh ‘basket’ is constantly agitated – this causes all the organic material to float to the top and get carried over the weir into the flot sieve. So you end up with a flot sieve full of all the organic content of your sample – and a lot of mud again!
While this was going on we were also moving the still damp trays of samples to the drying room – what luxuries – where they would dry out (surprise, surprise) before being distributed out to the various experts who will, in turn, feed their results back to us for incorporation into future reports.
So that was our day, though as usual there was a lot of chat as well, and we took the opportunity to pick Julia’s brain – a real professional! – on a number of subjects. One of our number is just coming up on University entrance and so was especially pleased to have a couple of people (he was quizzing Jo as well) to chat to about the finer details of various archaeology courses, and all of us were interested to have a professional take on the current upheavals caused by changes in the planning laws, economic troubles, etc.
There are more days planned (we’re not sure how many, check out the Archeox website for updates) to give the maximum number of people a crack at the whip. One of the downsides of this approach is that poor Julia has to start from scratch every day, and the speed of work stays rather low as no one can benefit from experience, but we have to give as many people as possible a chance to experience all aspects of archaeological investigation. This way people learn about the whole process, and appreciate there is more to it than just the ‘sexy’ bits one sees on Time Team.
So a big thanks to OA for a fascinating, if somewhat damp, day, especially to Julia for putting up with us all. On a personal note, many thanks to Steve for giving us a lift home – it wasn’t the walk to the station to get a No 5 bus per se; it was the lugging of the wellies, waterproofs, mugs, etc. David had given us a lift down but had, obviously, had to return the hire van as quickly as poss.
Not much to add. After starting with the wet sieving, I spent a lot of time taking grubby newspaper out of finds trays and replacing it with fresh -strange how bits of news catch your eye (anyone for the story of the cctv camera in traffic wardens’ ID badges?) and writing waterproof labels as the residue in every sieve needs a fresh tray. Some interesting things among the pebbles and gravel – a few bits of bone and some tiny shells.