craft knife or box cutter, large bucket, sponge, craft sticks, mixing containers and cups, disposable paper cup, safety glasses and gloves, black permanent marker, ruler
1. Carefully cut out back of papier-mâché numbers with craft knife to expose inside hollow area of numbers. Remove any interior pieces that would interfere with cement.
2. Position numbers, cut side up, on work surface. Determine thickness by placing ruler inside number with end against bottom; mark chosen depth inside each number using black marker. Spray mold release on inside areas of each number.
3. Wearing gloves, follow manufacturer's instructions to mix cement with water for one number at a time in mixing container. (Note: Cement will set up in mixing container. To ensure cement is workable throughout process and doesn't harden too quickly, work in small amounts.) Fill each number with cement up to drawn line; lightly tap sides to release air bubbles. For each number, make sure cement is set up to same depth. Let each number set overnight on level surface.
4. After cement has dried overnight, immerse numbers in bucket of water, softening papier-mâché mold. Carefully peel and remove paper from numbers. Let dry.
5. Wearing safety glasses, use wheeled glass nippers to cut mirror into random shapes. Position mirror pieces on numbers to gauge number of pieces needed. Use tile nippers to cut pieces to fit along edges of each number. (Note: For numbers such as "8" that are difficult to tile, paint areas with latex paint after grouting as noted in Step 8.)
6. Mix tile adhesive in disposable cup. Attach mirror pieces on top and sides of each number, leaving 1/8" area between each piece. Arrange pieces so raw edges align with edges of each number. Let adhesive dry overnight.
7. Follow manufacturer's instructions to mix grout with water in disposable container using craft stick. Apply grout to front and sides of each number, pressing in crevices between mirror pieces. Wipe off excess grout with sponge. Let dry. Rinse sponge. Continue to wipe grout haze off mirror tiles. Let dry overnight.
8. Paint untiled or smaller areas with latex paint in same color as grout; let dry. Apply sealant over grout lines on each number; let dry. Attach hanger to back of each number.