When to replace a cutting board

1. Run a fingernail across the surface. If it catches in grooves, soil and bacteria can sit below where a sponge reaches.
2. Look at it wet. Deep cuts hold water and show as dark lines. Those are the channels that will not drain or dry.
3. Smell it dry. A board that smells after washing is holding something in the grain or the grooves.
4. Check it on a flat counter. A warped or cupped board rocks under a knife, which is a cutting hazard before it is a hygiene one.
5. Look for splits, lifted glue lines and soft spots. A delaminating board cannot be resurfaced; it is done.
6. Then decide: resurface, or replace. Wood and bamboo can be sanded. Plastic and composite cannot.

This is the practical difference the food code language points at. A hardwood board is thick enough that sanding removes the scored layer and leaves a new flat surface — 80 grit to take the grooves out, then 120 and 220, then mineral oil until it stops absorbing. A maple or walnut board can go through that several times over a decade and come out genuinely renewed.

A plastic board cannot. It is thin, it softens under sanding rather than cutting cleanly, and the knife grooves are the whole material rather than a surface layer. The irony is that plastic boards were adopted partly because they are dishwasher safe and therefore easier to sanitize — which is true right up until the surface is scored, at which point the dishwasher is washing over the grooves rather than into them.

Composite boards sit in between and lean toward plastic: dishwasher safe, long-lived, but not resurfaceable. They get replaced rather than renewed, and they last long enough that this is a reasonable trade.

Glass is on that table only to be dismissed. It cannot be scored, which sounds like the perfect answer until you consider that the knife edge has to give way instead. A board that ruins every knife that touches it is not a hygiene solution.

Both work, and the deciding factor is not the material's inherent germ-resistance — it is whether the board in front of you is still cleanable. A well-maintained wood board and a new plastic board are both fine. A scored plastic board and a cracked, never-oiled wood board are both not.

What tilts it in practice is that wood can be brought back and plastic cannot, so a good hardwood board is the cheaper choice over a decade even at four times the purchase price. The one place plastic genuinely wins is raw meat and poultry, where a dedicated board that can go through a dishwasher at temperature is easier to be disciplined about. Two boards — wood for everything, plastic for raw meat — is the answer most kitchens should land on.

If the board you are replacing is plastic, the materials question is worth a second look while you are at it — our best non-toxic cutting boards roundup covers what each material publishes about itself.

• Never put wood in the dishwasher. Heat and prolonged soaking split boards and lift glue lines. This is the single most common way a good board dies.
• Wash and dry immediately, standing on edge. A board left flat on a wet counter cups.
• Oil wood when water stops beading — food-grade mineral oil, until it stops absorbing. Monthly at first, then when it looks thirsty.
• Use the biggest board you will tolerate. Cuts spread over more area, and the board scores more slowly.
• Keep a separate board for raw meat and run it hot. Separation beats sanitizing.
• Sand before it is desperate. Taking out shallow grooves is easy; taking out deep ones removes real thickness.