Complex sentence: A stack of three sheets of veneer was then put through a press, where each panel was subjected to a pressure of 150 psi between metal plates at 210 degrees F. This pressure and heat made the bond between the veneers permanent and the glue became insoluble.
Split into simpler sentences: A stack of three sheets of veneer was then put through a machine press. There each board panel was subjected to hydraulic pressure of 150 lbs per square inch between hot metal plates of 210 degrees F. This pressure and heat made the contact between the veneers permanent and the glue became insoluble.