Tempered glass could have spontaneous breakage without receiving any external force, which is the nature of tempered glass. The reason comes from nickel sulfide inside the glass. Nickel sulfide is α Nis in high temperature during the heating section of tempering procedure, when cooled rapidly in cooling section, there is no enough time for it to turn into β Nis of low temperature. The morphic transformation will last for ten of years after the tempering glass is installed, leading to spontaneous breakage. Heat soak furnace is assistant equipment to tempering. Upon completion of glass tempering procedure, the glass is tested in the heat soak furnace to ignite those tempering glasses with potential spontaneous breakage in advance eliminating rudimental Nickel sulfide and to avoid breakage happens after installation. This increases the safety and reliability of building. The machine is characteristic of computer in-process monitoring and controlling, multi curve display, data storage, record check and curve printing. This machine can be extended to be used in drying low frit heating and pre-pressing of bending lamination glass. The machine can be customized.