How to replace broken window glass and save £250 with this DIY job. HOW TO REPLACE A BROKEN WINDOW PANE Replacing the glass in an old sash window can be a meticulous but manageable process. Below is a general step-by-step guide. Remember to always wear appropriate safety gear, including gloves and safety glasses, during the process. Materials and Tools: - New glass pane (cut to size) - Glazier's points - Putty knife or chisel - Paintbrush - Linseed oil - Glazing putty - Multi-tool (like an oscil