Ceramic tile can develop hairline cracks for a variety of reasons. Perhaps you dropped something heavy on the tile, such as a cast iron skillet. Or if your ceramic tile was installed over newly laid concrete, the tile may crack as the concrete settles. Whatever the cause, you can remedy the cracks yourself without having to hire a professional. After the repair, your ceramic tiles should look as stunning as they did the day they were installed.
Apply a clear epoxy resin to any hairline cracks you find. Because hairline cracks are so small, you may need to use a toothpick to push the epoxy compound down into each crack. The epoxy should fill up the cracks completely.
Allow the epoxy to cure for several hours.
Match an oil-based paint to your ceramic tiles. Apply a small amount of the paint to the crack with a fine-tipped artist's brush. This makes the crack almost invisible to the naked eye.
Cover the cracked tile with several layers of clear urethane after the paint on the crack dries. This will prevent the paint from wearing away and also protect the tile.
Reapply the urethane every two years as necessary.