24th row

For this kiln the 24th row is where the skewbacks will sit to support the arch.
Before the arch goes up, angle iron needs to be on each corner, and on the top row pictured. The angle iron on the top row will be on each side, and it will support the arch. So when the kiln is heated, the arch will expand up and not out.
I have a quantity of angle iron from my old kiln. The old soft brick kiln was held together with many lengths of angle iron. It has been cut into lengths and many of the old pieces will be able to be used in this kiln. The longest lengths needed will have to be purchased (of course).

Here are some mortar qualities that I have learned:
I like using mortar is a sort of soupy consistency. When I purchase mortar it is in a trowel-ready consistency. I trowel about 1/3 to 1/4th of a bucket of mortar into a separate bucket & add water to near soupy consistency. In the very hot weather - I've been working in the summer heat waves of 100 degrees F + which is conducive to more liquid mortar - the hot air dries the mortar quickly. The last couple of days have cooled off dramatically. I can use a touch stiffer mortar on the hard bricks.
The hot face bricks on the inside of the kiln are hard bricks and absorb little water from the mortar. The back-up bricks on the outside of the kiln are soft bricks, and are held in water ( the half of the brick that will be mortared is immersed) just before being mortared. This way the porous brick does not absorb too much water from the mortar & dry it out before it is properly set.