Water popping is a term used when discussing the care and refinishing of wood flooring. The grain of the wood is raised when water is added to a floor prior to the stain. The moisture opens the grain of the wood, allowing it to accept the stain and producing a richer color that's otherwise not achieved. However, too much water can be used and the water that is being used should be spread evenly across the floor's surface. A tool called a "t" bar can help you achieve an even distribution, working much like a Squeegee.