A method of adjusting the pH of a strengthening melt for use in strengthening glass substrates, e. The first area of the dining surface has a light appearance. and under a vacuum in the range of 10\u22126 to 1,000 Torr, for a first period of 1-100 minutes, to form a partially dried layer; heating the partially dried layer to a temperature above 100\xb0 C. The first and second loads are cascade connected between a higher potential power source and the current input end of the first transistor.