After drying all the clay I collected, I then separated out orangey / yellow chunks, as these will be high in iron and affect the colour of the clay. I'll make a separate batch of iron rich Norfolk clay later.
I then added the dry clay into a bucket of water and let it slake down into a slurry, which I mixed with a blender to get smooth. I ran the mixture through a sieve but amazingly the clay was really pure and contained no stones or sand! This means it can be pulled out of the ground and thrown on a potters wheel as is.
The clay slurry was then poured into plaster moulds and left to dry to useable hardness. (Plaster helps to draw out moisture).
Once the clay had dried enough, I made several test bars, measuring 5 inches (my old school ruler didn't have cms).
I let the test bars dry completely before measuring them again - this is to get an idea of how much the clay shrinks when air dried.
I then fired two of the bars to 1050°C and the other bars to 1200°C. The tests below are on the lower fired bar.
After their firing, I measured ther lengths again and calculated how much they had shrink ((original length - final length) / original length) * 100 which was about 8%.
To calculate the amount of water the fired clay body absorbs, you first weigh the bars post firing and then submerge in water for 24 hours. The formulae is ((dry weight - wet weight)/dry weight)*100 and worked out as about 22%.
This is a simple test where you scratch the fired body with a nail to see whether it crumbles and if so, how much by. The nail didn't scratch the clay.
This is to see how the clay distorts when being fired and you simply place the test bar so it's not supported across the middle and after firing you check whether there is any bend in the bar. Happy to say there was no slumping.
The results of the tests indicate the clay is a typical earthenware surface clay with low (less then 15%) shrinkage and high absorption.
Fired to 1200°C
At the higher temperature the clay melted and stuck to the base I fired it on. Interestingpy the clay went from a cream colour into a mustard yellow, indicating the presence of iron, which makes sense, given all the orange bits I picked out.
The clay has almost no absorption now and resembles a stone or glass. This is because all the chemically bonded water has now been removed at the higher temperature and the crystalline structure of the clay now won't allow any water in.