Saturday, 26 September 2009

Experimental Archaeologist or Ancient Technology Specialist?

Who should conduct experimental archaeological experiments; archaeologists or practitioners of the particular technology under investigation? As a potter I wouldn’t dream of stomping onto an ancient site, spade in hand, and starting digging unless I was under the strict guidance of someone who knew exactly what they were doing. However there does see to be a tendency for archaeologists to construct a replica kiln, fire it, without consulting anyone who might know how to fire the thing, and then writing up the results in a learned journal as if it meant something. I’m sorry if this sounds like sour grapes but:

It was with interest that I read the recent article in Current Archaeology ‘Experimental Archaeologists Build a 14th-Century Kiln’ (CA No.235, P.7). As a professional potter and, dare I say it, ‘experimental archaeologist’ (Maybe I need a new job title!) I am delighted to see archaeology students getting to grips with ancient technology and impressed by the well built kiln shown in the photographs. But .... somewhat astonished by the timber consumption of three tonnes which is reported. In illustration 3 (not shown here for copyright reasons) the fireboxes are shown completely choked with charcoal and ash, a situation which would certainly limit or prevent temperature rise. Unlike some other heat based technologies kilns require a little and often policy when it comes to stoking, regular removal of ash build up and strict control of air flow to encourage fast ignition of the fuel.

A clean burning firebox in my kiln at Segedunum

It is also quite apparent that the walls of the structure are remarkably low, not a problem in a clamp type tile kiln where the tiles are stacked within, and well above these ‘proto walls’ which are then extended upwards as temporary daub insulation. In the illustration the chamber is not even filled to the height of the walls making it a remarkably inefficient load; fully loaded kilns fire far more efficiently than half empty ones. The top of the tile pack is apparently not capped as it would have been, again with wasters and temporary insulation. All of these factors will adversely affect the firing of the kiln.

Temporary daub dome being removed from Segedunum Kiln

The fuel itself must be completely dry; long term, managed storage of timber is something that wood firing potters accept as part of the process. Finishing of firings would often involve the use of very fast combustibles such as dried gorse (hell on the hands but great for raising temperature).

The thing that has to be borne in mind is that the people who fired these kilns had almost certainly been doing it all their lives and had learned the skills from their parents and grandparents. I have been firing wood kilns all my potting life and still acknowledge that I have a lot to learn about the process.

If this was the first firing of this kiln its firing characteristics would have been quite different to those of subsequent firings There is a risk that calculations for large scale ceramic industries are based on experiments like this one, giving a very distorted view of fuel use, manpower requirements, land usage, etc., etc.

The Norton kiln could certainly be fired on a lot less timber. I regularly fire an experimental La Tène-derived, surface built, updraft kiln of turf and clay construction, and even though this is a Romano-British kiln the firing characteristics of which are similar to this type of kiln. Its chamber would happily accommodate something in the region of 200+ Medieval tiles and yet it uses less than 150kg of timber to reach 1000 degrees C over a period of 6 to 8 hours depending on weather conditions. That is only about 5% of the fuel consumption recorded for the Norton Kiln, even given kiln differences and a margin for error it's difficult to see how you'd get up to 3 tonnes.

I’m not saying don’t experiment, in fact I’d like to see much more experimentation. What I am saying is; if you experiment with ancient technologies seek out the best expertise you can find. I love working with archaeologists and by working together we can get great results that combine the best aspects of both disciplines.

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Tuesday, 8 September 2009

Stibbington Potters Wheel - Stick or Kick?




The case for classing this as a stick wheel:

Firstly I Note that radii drawn through the holes that I have marked as 1, 2, 3 on the image above (Fig.1), divide the wheel into three roughly equal segments, this would be a very sensible placing for stick holes. Furthermore holes 1 and 2 are shown in drawings, to be elliptical at the upper edge, and also appear to be so in the photograph in 'The Pottery Kilns of Roman Britain' Swan (1984), the long axes of these ellipses are at an angle of approximately 50 degrees to the radius of the wheel, descending left to right when the hole is at 12 o’clock on the wheel. The fracture of the stone at hole 3 has removed the upper surface but it too seems to exhibit an elliptical shape in approximately the same direction. When operating a stick wheel, the stick is inserted into one of the holes and force is exerted in the direction of spin, anticlockwise in the case of a right handed potter. Once the required speed is achieved the stick is withdrawn and the natural position for this to happen is when its hole is at approximately 2 o’clock, the stick is then naturally brought back to the right hand side of the potter. When the hole is at 2 o’clock the direction of drag will be approximately 50 degrees to the radius. As the stick leaves the hole it drags slightly on the trailing edge of the hole and over time this slight drag will cause the hole to wear into an ellipse. I note that some of the other holes also exhibit this same elliptical form. My own stick wheel (Fig.2) has started to exhibit exactly the same type of wear even though it has thus far made only a few hundred pots. Other, apparently random, holes may be the result of balancing, attachment to a frame, a prior existence as a mill wheel (quern), or additional stick holes when the original ones became too worn. The fact that small stones are jammed in two of the holes may be accidental but could, depending on the depth, be a device to prevent the stick sitting too deeply into the hole and becoming jammed or difficult to remove at high speed, once the holes had become excessively deepened through wear. The large central hole in the flywheel would readilly accomodate a raised wheelhead in the form of a solid log with a hole bored up the centre in which the fixed central shaft would pivot (Fig.4).


It is possible that the wheel has seen service as both a stick and a kick wheel. The worn band on the upper surface of the stone at approximately the midway point between the inner and outer rims corresponds almost exactly with the wear pattern that is developing on my own kick wheel (Fig.3). This type of wear could also develop from using the foot, or even a piece of wood, as a break, something that I do on a regular basis when using a stick wheel. A flywheel of this type could easily have provided the motive power for potters’ wheels for several generations and been required to serve different purposes for different masters. Equally it may have been used under different circumstances by the same potter. A stick wheel has several advantages over a kick wheel; not having a cumbersome frame it is inherently more portable suiting the purposes of an itinerant potter ideally; a far higher speed can be generated with a stick than can be achieved with the foot, making the production of fast, cheap ware far more attainable; its low wheel head is almost essential to the making of very large storage vessels or amphorae. The kick wheel on the other hand has the following advantages over the stick; being fixed in a frame makes it far more stable and therefore better suited to the production of finer wares such as Samian or Nene Valley colour coated wares; its setup allows for a seat and therefore much more comfortable working conditions

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Friday, 4 September 2009


Just a very brief interuption to the flow of this blog to note the most joyous news that today I became a grandfather. TAAAAAARAAAAH!!

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Wednesday, 2 September 2009

Questions, Questions, Questions!!!

Working at Museums, English Heritage Sites and the like, with a mixed audience of children and adults, I am constantly presented with new questions. Sometimes I have to confess that I simply don't know and I add the question to my ever growing list of things to find out!

Here I am demonstrating Roman Pottery as drawn by Katie

These are some of the more common questions and requests that I have had over the past few weeks while working as Gaivs the Potter (Yes I do dress up when needed!!):

Why do amphorae have pointed bases?
Where did amphorae come from and what did they carry?
How did the Romans make Samian Ware?
Can you show me how a Nene Valley hunt cup was decorated?
How did the Romans fire their pots?
Why do some Roman pots have faces on them?
How did the Romans use moulds to make their lamps?
What did a Roman potter’s wheel look like and how did they use it?
Can I have a go at making a moulded goddess figure?

Where did the clay come from?

These questions I can answer through a combined use of my handling collection, demonstration, hands-on activities. Other questions are not so easy to answer, some will require considerable research, some require experimental reconstruction of kilns and equipment and some will never be answered.

Some of these questions include:

Why didn't the Romans glaze many of their pots?
How long did a cooking pot last?
Why does the surface texture of Samian ware vary so much?
How hot did the Romans fire their pots?
How did the Romans package and transport their pots?

One thing I can be certain of is that; as long as I continue to engage with the public, and especially children, I will never be short of topics to research.

Someone kindly!? took a video of me working with moulds and entertaining a crowd at Corbridge the other day and has put it on Youtube: (Don't laugh, you have to entertain to teach.)

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