In order to create the body of work required to fill and subsequently fire the replica Julfar kiln, Updraft Two, I need to produce a strong and reliable clay. I estimate a minimum of half a ton of clay will be required to produce the one hundred or so pots needed to pack Updraft Two and provide for the workshops offering the unique opportunity to work with this local clay.
In the absence of any processing machinery, dauntingly, this quantity of clay will have to be processed and refined by hand, echoing the technique used by the Julfar potters.
In order to transform the raw clay into a workable state it needs to be soaked, washed, sieved and dried. To achieve the hand processing of such a large quantity of raw clay I have designed and constructed, a series of simple devices.
This apparatus consists of a drill with a plaster mixing attachment, a one meter square rectangular sieve made from mosquito screen, a processing line consisting of plastic boxes and a series of ‘clay drying hammocks.’ With the help of these devices contaminants will be removed from the raw clay precipitating a purer, denser clay.
However the process of refining the clay does not end there. The pure clay, free from stones and other impurities is very plastic and sticky and shows a high shrinkage rate; it requires a temper to ‘open up’ the clay body and reduce shrinkage. The Julfar potters may have used different tempers during the nine centuries Julfar ware was produced. Ethnographic sources cite crushed sea shell as well as a different types of course clay; which would account for the distinctive rough hackly fractures that can be seen in most Julfar ware body types.
Julfar ware was made using coils of clay and a ‘dawwar’ a small concave disk that was rotated with the foot to help maintain the form and shape of the pot. As the pots were hand built the temper used could be fairly course. To create my body of work I will throw the pots on a wheel, which will require the production of a finer, smoother clay. I am currently experimenting with different percentages of sand temper sourced from Ras Al Khaimah and Abu Dhabi. My aim is to create a strong throwing clay that has the capability to withstand a high degree of thermal shock and showing a moderate amount of shrinkage, circa fifteen percent.
The kilns used to fire Julfar ware were basic updraft kilns where the pots were placed on a checkered platform directly above the firebox. Controlling the rising temperature was difficult and the rampage rate could have been as high as 250 degrees centigrade per hour, putting a tremendous amount of stress on the clay body. For a successful firing of Updraft Two, I need my clay to be able to cope with such steep rises in temperature and not suffer from cracking and warping as a result of the intense heat. I therefore need to subject each clay mix to a series of sharp temperature increases, which will be achieved and measured in electric kiln, in order to adequately evaluate its resistance to thermal shock. Only then can I be certain of producing a clay with the most positive predicted outcome, the survival of the Updraft Two firing.