Ceramic is a sturdy material, but it's prone to breakage over time. If you have a ceramic coffee mug that's developing cracks or has lost a large chunk from the rim, or even the entire handle, you can repair it. Repairing a ceramic coffee mug is a straightforward process and can be done at home.
Inspect the crack. A crack that has cannot be budged or separated by your fingers is one that likely does not go all the way through the ceramic and does not need to be treated. If you find that the crack is loose and that the edges can be pulled apart even slightly, a repair is necessary.
Push the sharp edge of a razor blade into the crack to open it a little wider. Rock the blade back and forth gently rather than trying to press it straight down. You are trying to get an opening for the adhesive to enter.
Mix a dime-size amount of epoxy with a dime-size amount of hardener. Epoxy comes with its own hardener. While in many cases the epoxy and hardener are in a dual syringe for simultaneous application, the syringe tip will produce more epoxy than is necessary. The mixing should be done on a piece of cardboard that can be thrown away later.
Use a toothpick to apply epoxy into the crack. Work quickly, because you have between three and four minutes before the epoxy starts to cure. Be neat as well, because epoxy can dribble out of the crack and harden into place.
Wrap a rubber band around the body of your cup to hold the edges of the crack together tightly.
Allow the coffee mug to sit until the epoxy cures. The package that the epoxy came in will tell you how long that takes; depending on the epoxy, it can take an hour to a day.
Remove the rubber band.
Assemble all the pieces of the broken coffee mug.
Set the main body of the ceramic mug into the sand with the part that needs to be repaired pointed up. This will secure the mug while you work with both hands.
Brush any debris or dust out of the broken edges with a paintbrush.
Mix a dime-size amount of epoxy with a dime-size amount of hardener.
Use a toothpick to apply the epoxy mixture to the edges of the break on the main body of the ceramic mug.
Set the broken piece into the main body of the mug and hold it in place for at least a minute. While a crack needs to be held together with rubber bands, a chip or a broken handle cannot be bound in this way. Simply allow the glue to start to cure before you let go of it.
Allow the epoxy to cure completely.
Remove the ceramic coffee mug from the sand and wash as you would normally.