The first day of school in the China falls on 1 September, or the first Monday following if September 1 is a Friday, Saturday, or Sunday. In northeastern China, schools open on Monday in mid-August after summer vacation.
3) Improper heating profiles setting lead to unbalanced heating zones temperature inside heating furnace, which causes uneven glass temperature on both different parts of the glass sheet and between the top and bottom glass surfaces, thus may brings irregular white haze on glass surfaces.
Variations in glass color resulted from a myriad of different causes including the strata of the sand source, the mineral in the soil of the of the trees burned to produce potash (an flux alternative to soda), and many others known and unknown (Toulouse 1969a).