In general, porcelain sinks are durable, but certain situations can lead to cracks and chips. Cracks often occur when you expose the porcelain to extreme temperature changes. For example, pouring boiling water into a sink that's cold to the touch can cause thermal shock, which results in cracking. Other common causes include dropping a heavy item on the sink, nearby vibrations, continually leaning on a sink in the same spot, and ordinary wear over time.