The cloudless skies have re-energised me and I've got loads done this week. the kiln is really taking shape - chimney finished (8ft from chimney floor, which seems short but it's a small kiln) and the arch is in place.
Still quite a bit of cutting to do to fill in the side wall of the chamber, then cover with secondary insulation + finish the firebox roof. Next week I'll measure up for all the metalwork.
Alongside this I've been working with many of the non-stoneware clays that I have collected, including local Fen clays, for an 1150C firing in the new kiln. I have managed to use some successfully, with homemade grog additions, but there's been a lot of cracking going on, with a very late sudden shrinkage that indicates highly plastic smectite clay minerals. My reading confirms that this is often the case with these Fenland clays, making them very difficult to work with. I have found one seam of sandy clay that is quite useable as it is (fantastic!) but only have a small sample of it + the area I got it from has now been quarried out.