In the grand scheme of things, a chip in your ceramic floor tile isn't a big problem. But you are reminded of the chip every time you sweep the floor, have company over or walk in the room. Replacing ceramic tile costs a fair amount of money to have done professionally and takes a long time to do yourself. Luckily, chipped ceramic floor tile can be repaired without too much labour or expense.
Clean the chipped tile using soap and water. Rinse it well and dry it with a hair dryer for 15 minutes. Ceramic tile is deceptively absorbent.
Use the paint brush to paint the primer/sealer to the chipped portion of the tile. Do not to get any primer/sealer on the glazed portion. Apply a thin coat. The primer/sealer should not puddle. Wait two hours for the primer/sealer to dry.
Paint the chipped portion with a thin coat of high-gloss paint. Stand back and look at your handiwork. If the colour of the chip matches the rest of the tile, you are ready for the next step. If not, wait 24 hours for the paint to dry and add another thin coat. Wait 24 hours for the last coat to dry.
Mix the epoxy. Squirt equal amounts of epoxy from each section of the epoxy syringe onto a paper plate, and stir the two puddles of epoxy mix together with a toothpick.
Daub the mixed epoxy onto the chip in the tile with your toothpick. Add small amounts at a time until the chip is level with the rest of the tile. Allow the epoxy to dry for 24 hours before allowing anyone to walk over it.
Have your high-gloss oil paint made professionally. Many home-improvement or paint stores (Home Depot, for instance) will make custom colours for you. Bring in one of your spare tiles if you have one. If not, a picture of the chipped tile will have to suffice. If given a few days (maybe even hours), they can match the colour exactly. Your local hobby shop is the best place to find primer/sealer. There they sell it in tubes small enough for your purpose. Be sure that the epoxy you buy is clear and waterproof.