The document specifies a method of determination the (dilatrometric) transformation temperature of a glass by means of the termal expansion method. This temperature characterizes a certain glass transition range from the elastic brittle (low temperature) state to the viscous (high temperature) state of glass. The transformation temperature has been found useful for specifying cooling programmes and estimating the upper temperatur limit of applicability of the respective glassware. This method is applicable to all glasses of normal bulk-production compositions.