It's surprising how easy it is to put a crack in a bathroom sink. Just dropping a glass can do the trick. If the sink is porcelain, patching the crack is as easy as buying and applying an epoxy, but other materials such as Corian may be a bit more challenging to repair.
Porcelain Repair Kit
For a hairline crack in a porcelain sink, consider a porcelain epoxy kit. They are available at hardware and art-supply stores, they cost between £3 and £6 and have easy-to-follow instructions. The major disadvantage is the look; these kits generally come only in white, so if your sink is coloured, the repair will stick out. But if you don't mind the imperfection, this is an inexpensive way to get more life out of your sink.
Corian Sink Repair
Many sinks are made of Corian, the brand name for a solid-surface material made by the manufacturer DuPont. The fix-it blog naturalhandyman.com suggests two products: Dupont Seam Sealer, a two-part epoxy; and Cyberbond, which is similar to super-strength glue but is best used to repair Corian parts that are clamped together.
Sometimes the sink is so severely damaged that a simple epoxy won't do the trick. Or perhaps you don't want your sink looking anything less than brand-new. In these cases, replacement may be a better option than repair. Expert Richard Trethewey points out on thisoldhouse.com that it's impossible to make cracked porcelain good as new. Replacement is ideal, he says, especially if you're due to replace an ageing faucet or water-supply fixtures.