This week I have been mostly making….a ware chamber.   Leave a comment

The first course of the ware chamber is bedded on ceramic fibre paper to ensure it has a perfectly level surface

The first course of the ware chamber is bedded on ceramic fibre paper to ensure it has a perfectly level surface

The kiln I am building has the ware chamber (the area – strictly speaking volume – where the pots are placed for firing) located above the fire boxes. The ware chamber floor is the fire box roofs. It has approximately the same length and depth dimensions as the base of the kiln and is just over a metre high , however this varies because the top of the chamber is arched. The internal volume is approximately 0.85 cubic metres (30 cubic feet) although not all of this can be used for stacking pots as shelf-free space must be left over  the flues which bring the heat, gasses and flames into the chamber from the fireboxes below.

 

 

 

Once the first ware chamber course is complete the corner supports can be put in place. These are held in place by threaded rods.

Once the first ware chamber course is complete the angle iron corner supports can be put in place. These are held in place by threaded rods.

The ware chamber is built with HTI (High Thermal Insulation) bricks. These are similar to, what in the UK, are called ‘breeze blocks’ or ‘Durox’, but they are very high temperature tolerant and even more thermally insulating. The material is like pumice but with a uniformly small bubble size. I read somewhere, many years ago, that it was developed as part of the US space programme for insulating the Space Shuttle during atmospheric re-entry and earned the craft the nickname ‘the flying brickyard’.

 

 

 

 

By the time the sixth course is finished the chimney outlet has been bridged using a piece of kiln shelf as a lintel. Note the thin slivers of HTI brick needed to make this wall the same length as the firebox walls and the way the bricks have been cut to allow a vertical panel of bricks to be removed

By the time the sixth course is finished the chimney outlet has been bridged using a piece of kiln shelf as a lintel. Note the thin slivers of HTI brick needed to make this wall the same length as the firebox walls and the way the bricks have been cut to allow a vertical panel of bricks to be removed

The HTI bricks are cut from a larger slab of material after it has been made and are therefore very uniform in size.  This is in contrast to the firebricks used for the base which are cut before they are fired and can vary in length by as much as 5mm with the majority being slightly longer than their nominal length of 230mm. This means that a row of 6 HTI bricks is almost always shorter than a row of 6 heavy fire bricks and necessitates cutting thin slivers of HTI brick to make up the length. Fortunately HTI bricks are easy to cut. The second, third, fourth and fifth ware chamber courses  have a gap in them at the back where the flue to the chimney will join and at the front of the chamber the bricks are laid such that they can be removed to allow the pots to be placed into the chamber. Although strictly speaking this panel of bricks is not a door, for simplicity’s  sake that is how I will refer to it from now on.

 

 

 

 

 

The ware chamber walls are complete, the door bricks have been cut so it can be laid in row-lock and two 'spy-hole' bricks have been put in.

Viewed from the front, the ware chamber walls are complete, the door bricks have been cut so the brickwork can be laid in row-lock and two ‘spy-hole’ bricks have been put in.

The remaining 7 wall courses are straightforward and similar and and when they were complete I took down the door bricks and cut one of each alternate course in half so that the door wall could be built more stably. In a couple of places I replaced a brick with two wedge shaped bricks one of which was slightly too long for the space available for it. This made it stick out from the wall which will allow me to pull it out during a firing to see what is happening in the kiln and pull out test pieces.

Finally, on each side of the kiln, a piece of angle iron is supported by brackets on the corner supports just above the top of the chamber wall. This is the ‘arch support’ which will prevent the arch, which forms the roof of the ware chamber, from pushing outwards and collapsing.

Next, the tricky bit, building an arch.

 

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