Complete instructions as well as more examples can be found on my website. http://www.gardensandcrafts.com/bbart.html
Step 1: Finding and Preparing your Bowling Ball
Always start with a clean and prepped bowling ball. Use rubbing alcohol or vinegar to get the wax finish off the ball. Sand lightly to rough up the surface, then rinse and dry the ball before painting or gluing.
Step 2: Painting your Bowling Ball
Use a paint designed for plastics, or use a plastic primer before painting. I find that spray paint is easier to work with. Always choose a paint that is rated for outdoor use.
Sealing a project with 2-3 layers of an outdoor polyurethane will help the paint job last longer. This ball is painted with a copper colored paint and has been in my garden for four years now.
Step 3: Mosaic a Bowling Ball
There are a variety of adhesives that can be used, based on what type of material you will be applying to the ball. I find that thinset mortar, construction adhesive, clear silicone or premixed concrete patch work for most things. Mac Glue, Plumber's Goop and Silicone work well for glass. Make sure you have proper ventilation when working with glues, following the manufacturer's instructions.
I used Plumber's Goop to apply these glass globs to the ball. The ball was already a pretty bluish-green color, so I did not feel the need to paint it first. I did not grout it.
Step 4: Glass Globes on a Bowling Ball
Step 5: Grouting your Bowling Ball
Always use sanded grout as it holds up better outdoors. Adding Admix to the grout instead of water will strengthen grout and help to prevent mold and mildew. Mix the grout so that it is the consistency of a stiff brownie batter. Always wear a dust mask when mixing grout to avoid breathing in the grout dust. It's easier to apply the grout with your hands on a round surface. Wearing two pair of latex or nitrile gloves when applying the grout will protect your hands from chemicals and from getting cut by any sharp edges. Apply the grout so that it gets in between all the pieces. This adds strength to the mosaic.
Allow the grout to set up for 10 minutes, then wipe off excess grout using a dry cloth or sponge. Allow grout to set up for another 10 minutes, then wipe the ball down with a damp sponge, buffing the tiles as you go along to remove any grout film.
Have a bucket of water handy and use the water to keep your sponge clean as much as possible. Never put this water down your drains, as any grout residue can set up in your pipes and cause a blockage. Pour any water outside and then wipe out any grout residue that remains and dispose of it in the trash.
Sealing the grout is not an absolute necessity, but I find the grout resists stains better that way and lasts longer outdoors. Sealer can be applied after grout has set up for at least 24 hours. Follow manufacturer's instructions, as they may be slightly different depending on the brand you use.