The work was getting too heavy and difficult to continue without transporting first so I moved it home and carried on building in situ.
In order for the core sample to be secure I have built it on top of an old fire grate upside down. As I was adding, I decided to build a fire underneath to dry the work as I progressed. As it grew, it also shrank! Obviously the clay at the bottom is shrinking while I build and I keep moving the metal pipe upwards so that it doesn't crack the clay below under compression. However, in doing this the uppermost clay is fatter and wetter so it is hard to judge what is going on!?