Most kilns are built mostly out of insulating fire brick. K-23 is the base
standard though there are others. The basic kiln is nothing more than an
insulated enclosure to retain heat. All kilns should be vented to allow
fumes to escape, and in the case of fuel fired kilns (gas, oil, wood) a
chimney is needed to vent the combusted gas. There is really too much to
explain is a quick e-mail response.
If interested and you are in the Northeast, I have a 29 cu ft + four burner
propane fired catenary arch downdraft kiln I'd like to sell. It would need
to be dismantled to move, but the sale will include all the soft and hard fire
brick, the burners, silica carbide shelves and assorted posts. $500 takes it
Check the Rhodes book out. I built my kiln from a plan in that book and
there are many others.