The Hearth
After a false start, in which we made the replacement hearth too long, we shortened it to the correct size and were able to re-build the firebox. We decided to re-use some old mullite tiles for the hearth, as they would withstand the firings far better than Roman tile fragments, and laid them directly on compacted soil using daub as a ‘cement’. We did not extend the hearth in front of the lehr as the new floor would cope with any hot ashes and heat radiating from the stoke hole.

The Firebox
We re-used the daub walls for the firebox as they had not appreciably deteriorated, except for the entrance to the stoke hole, which needed five-inch wider walls as well as a replacement keystone. In the end, it was re-built as a single unit, using a plastic bucket as a form for the arch. It shrank as it dried, so needed building up to the correct height several times. When finally dry, the gaps between it and the old walls were filled with fire cement.

The back wall also needed to be longer, and we found that two HTI bricks laid at 45° sufficed, with two half bricks above them, and the gap at the top filled with daub. About a one-half-inch difference in thickness between the walls and the bricks was filled with a sheet of daub, which had to be stuck in place with fire cement once it had dried.

The metal bars had bent in the heat, so had to be turned 90°, as well as having to be lengthened by ten inches. These bars will eventually be replaced with ceramic bars.

The Walls and Roof
The walls of the chamber were rebuilt in the same manner as the original walls, but with the back and front walls needing another row of bricks and another strip of one inch-thick ceramic fibre blanket. The two end walls were secured by four tie bars: the outer bars pulling the walls inwards and the two inner bars pushing the walls outwards, thereby keeping the walls in place and allowing them to resist movement caused by the large cracks and splits that they had previously acquired during use. These cracks and splits were filled with fire cement.

Both the double-layered floor and the roof had to be extended with extra kiln batts. We also made two flue holes and put a double layer of LTI bricks on top of the kiln batts to add to the insulation.

We had two new Type K thermocouples which we inserted in the back wall, at each end, and near the top of the third row of bricks.