The reason that the StarCat doesn’t use ceramic blanket insulation on the sides is because of the compact firebox size. Ceramic insulation is 1″ thick, and to put two layers in the firebox would deprive you of crucial volume needed for fuel and clean combustion.
If you have chosen to source your bricks locally, please be aware that there are many different styles of firebrick that are meant to serve different purposes. For example, the firebrick that is used in a house wood stove or fireplace is designed to allow heat to pass through the brick to heat your home. In contrast, with a maple syrup evaporator, you want insulated firebrick, which keeps the heat inside the combustion chamber rather than allowing it to escape. You want to keep the heat focused on the evaporator pan. This will result in a stronger boil and increased evaporation rate.
The StarCat Firebrick Kit is designed specifically for use in this evaporator. This style of firebrick will help keep the sides of the arch cooler and help keep the heat in.
We strongly discourage using the 1/4″ thick “arch paper” for insulation. In our experience, this product had virtually no insulation value and crumbled to dust after the first fire and cool down cycle. We recommend insulated firebrick as your best solution.