A reader needs help repairing cracked tiles. (Reader photo)

Q: We installed porcelain tile in our hallway and kitchen 20 years ago. Over the years, one or two tiles in the kitchen have developed hairline cracks. When we remodeled our kitchen five years ago, we replaced those with some spare pieces. But there must be a problem with the subfloor, because both replacement tiles have also cracked. They are in a highly visible location, and we have no more spare tiles. On the Internet, there are suggested remedies such as applying an epoxy in the crack, painting over with an oil-based paint that matches the tile color and then covering the paint with polyurethane. Would that improve the situation?

McLean, Va.

A: Given the options of living with the cracks, replacing your whole floor or trying to patch, what do you have to lose by trying a patch? But rather than buying epoxy and enough different colors of paint to match the mixture of colors on your floor — and depending on thin layers of paint and polyurethane to keep that look over many years — use an acrylic putty tinted to match the background color of the tile, topped by dabs of accent color and a clear coat. This way, if some of the patches wear, you’ll barely notice.

Compared with the cost of buying small containers of all the things you would need to do the epoxy repair, you’ll probably save money by buying a kit with acrylic putty, such as Cal-Flor Mix2Match TileFix ($21.86 at Home Depot). The kit includes a tube of acrylic putty plus mixing materials, little bottles of color tint and a small bottle of lacquer for the topcoat. Cal-Flor Multi-Surface Repair ($49.99 at Lowe’s) is basically the same except that it has more materials and a wider range of color tints, making it a more versatile solution if you have a lot of different surfaces that need patching, including wood, vinyl, laminate and stone, as well as tile. Each kit includes one or more cardboard pieces printed with lines showing how much putty to squeeze out and mix with the appropriate number of drops of tint to match colors on a chart that’s included in the kit.

Online reviews from people who have purchased the Cal-Flor kits say the materials work well, but many report that the color charts are virtually useless except as a place to start. Plan on needing to adjust and test the color several times to achieve a good match. The putty dries darker than what you see when it’s freshly mixed. So, with each color adjustment, spread a dab on a piece of cardboard and blast it with a hair dryer so you can judge the final color. Cover the rest of the mixed putty with plastic wrap in the interim so it doesn’t dry prematurely.

The coloring is very concentrated, so don’t try to adjust a mix by adding a drop of color; instead, mix the drop into a fresh squeeze of the putty, and then mix a little of that into the putty you are trying to color-adjust. To lighten a color, add more untinted putty. There is also a white tint that you can use for adjustment.

Once you achieve a color that’s a good match for the base color of the tile, fill the cracks and smooth the putty with the plastic spatula included in the kit. Or, if the tile is heavily textured, you might want to smooth over the patch with a gloved finger, which will follow the bumpy texture better. Clean smears with a damp cloth before the putty dries.

After you patch the crack with the background color, match the mottling on the tile by adding streaks or dabs of the accent color or colors. To do this, the instructions suggest pulling away most of the cotton on a swab, leaving just a wisp to act as a thin paintbrush. Mix a few drops of the color tints to create the appropriate accent color, and put three drops or so of the lacquer on a piece of cardboard. Dip the wisp into the color, drag it through the puddle of lacquer a few times, then touch up the color of the patch. Practice on cardboard first until your touch-ups match the color variations on the tile. If the cotton wisp turns out to be too thin to match the color variations on your tile, try using a thin artist brush with the bristles cut off close to the ferrule. This leaves them stiffer, so you can use the brush to dab on the color with a down-and-up motion.