Mix your cement completely to get rid of lumps until the consistency resembles that of cake batter. Pour cement onto one side of the window in small puddles dispersed over the area of the window.
Use a natural bristle scrub brush to spread cement under the edges of the metal came, the strip between the glass panes. Hold your brush sideways, perpendicular to the cames, as you push cement underneath. Adjust the angle slightly when brushing the border cames so as not to distort their shape; hold at an angle slightly less than 90 degrees. Fill all the cames’ edging with cement.
Dust a thin layer of calcium carbonate across the surface of the window to help the cement set. Wait several minutes, then dust extra calcium carbonate from the window surface.
Scrub the excess cement off the glass panels with the brush. Hold your brush parallel to the cames as you scrub to avoid removing the cement under the cames, then brush the extra cement into the cement tub. Use strong brush strokes, but don’t apply a great deal of pressure to the glass.
Repeat the process on the opposite side. Use a separate, clean bristle brush when removing extra cement. Brush off extra calcium carbonate by hand.
Spread calcium carbonate across the surface of the glass a second time. Use the abrasive, absorbent qualities of the compound to scrub the extra cement from the window pane. Repeat on the opposite side, brushing off cement and calcium carbonate as you go.
Use a stopping knife to press the edge of the came close to the pieces of glass. Smooth out the came so that no lumps are visible underneath. This is not necessarily with a narrow came measuring less than 3/8 of an inch in width. Repeat on the opposite side of the window.
Use a lathekin to scrape traces of cement from the came’s edges. Be sure not to scrap the underside of the came so as to preserve the cement underneath. Scrub the surface as you go to assist in removing debris. Repeat on the other side. Continue brushing and scraping cement from the cames and the glass until the window appears clean. Do not clean with liquid.
Lay flat and let dry for 24 to 48 hours to let the cement dry and set completely. Inspect the window periodically as it dries for any traces of cement that may have leaked from underneath the came, and scrub cement that spreads to the glass.