Porcelain, like ceramic, is a clay-based tile that is generally topped with a high glaze. Usually the only option to repair cracked tiles is to replace them. However, if a crack doesn't go all the way through the tile it is possible to temporarily fix the tile. Porcelain repair kits are available at home improvement centres for repairing chips and small cracks. Although the repair is not perfect, it is often much less expensive than replacing tiles.
Clean the area around the crack. Sand the crack with a fine-grit sandpaper and wipe it off with a damp cloth. Allow the porcelain tile to dry completely.
Mix the two-part epoxy from the repair kit according to its instructions. Some systems will require you to stir together equal amounts of the two compounds on a paper plate, while others come in self-mixing containers.
Apply the epoxy over the crack in the surface of the tile. Use a toothpick to work it down into the crack. Continue adding the epoxy to the crack, forming it slightly above the surface of the tile.
Let the epoxy dry for eight hours. sand the epoxy with a fine-grit sandpaper until it is flush with the tile surface. Wipe the dust off with a damp cloth.
Brush small amounts of the enamel onto the patch, attempting to blend the edges of the repair area with the surrounding tile. Let it dry for eight hours.
The repair kits come in different colours. Although you most likely will not find an exact match, use a colour that closely matches the tile.