Wooden boards should never be placed in the dishwasher, or left immersed for long periods, as the wood or glue may be affected. To prevent cracking, cutting boards can be treated when they start looking dry. A standard recommendation is 5–7 times a year, or as needed. A light food-grade mineral oil is a good preservative for wooden cutting boards, as it helps keep water from seeping into the grain. Alternatively, one may also use a food-grade drying oil such as poppyseed oil, tung oil or linseed oil. The first two dry much faster than linseed. Most commercially available linseed and tung oils are not “food grade”, as they contain metallic driers. In general, edible savory vegetable or olive oils are not recommended because they tend to go rancid, causing the board to smell and food to pick up the rancid taste. When heavily or deeply scored, wooden boards need to be resurfaced as scoring can harbour bacteria. Boards can be easily resurfaced with various woodworking tools, such as scrapers or planes, even sandpaper.