any shape such as circular elliptical or other curved configurations in one embodiment the oven is circular in shape and has a diameter of less than 15 feet in the embodiment of fig1 the transport system is a rotatable turntable 102 that rotates about a single central axis 103 supported by radiating spokes 104 the rotatable turntable 102 may be driven by a driving device such as an electric motor not shown alternatively the transport system may be a chain driven tracked path hollow pedestals 105 are connected to the transport system and may be conveyed though the curved oven 101 along a path individual molds 106 are mounted on the pedestals 105 the molds 106 may be fluidly connected at a lower opening to the hollow pedestals 105 the path of the rotatable turntable 102 leads into an entrance aperture 107 through the oven 101 and out an exit aperture 108 the apertures 107 108 may be shaped substantially like the profiles of the molds 106 and pedestals 105 to beneficially reduce the amount of heat loss from the oven 101 as the transport system conveys the molds 106 and pedestals 105 through the oven 101 the shape of the apertures 107 108 may be for example 10 greater 5 greater or a smaller percentage greater than the profile of the pedestal 105 and mold 106 conveying through the.