1. A furnace comprising: a generally cylindrical furnace body having a closed end and an open end; a frame pivoted to a ground member, said frame supporting said furnace body for rotation at various angles in a reclined position from said open end and in an inclined angle towards said open end; a burner to heat said furnace; and, at least one hinged door, arranged to close said open end of said furnace; wherein non-tapered walls of an interior of said furnace are substantially parallel and cylindrical from said open end to said closed end; and wherein said at least one hinged door is hinged to said frame and is capable of inclining and reclining in unison with raising and lowering of said furnace.