How do you fix a warped cutting board? It’s surprisingly easy if you’re patient.
TL;DR: Your cutting board is more wet on one side vs the other. Fix it by letting the convex side dry out more.
Here’s the expanded answer. First it’s important to understand why it warped in the first place. Cutting boards warp for two main reasons; they were made poorly or they weren’t being cared for properly. Since most cutting boards are made well, let's focus on proper care and what causes it to warp.
After using or washing a cutting board it’s normal for it to be wet—this is the critical time when a cutting board will warp. If one side of the cutting board is left wet while the other side is able to dry you will surely end up with warping; in fact it’s so predictable that it’s easy to replicate. Check out this experiment and guide by Earlywood. We warped one of our own boards one night after washing it and leaving it on a wet dish cloth all night and the following day—a common mistake... These photos are from our own experiment.
The science behind it is very straight forward. Imagine your cutting board as a sponge, it has lots of pores and fibers that are capable of absorbing water. And just like a sponge, when it absorbs water it expands. So what happens when one side absorbs more water than the other? That side expands and grows larger while the other stays dry and constricted. It’s this difference in expansion that causes the warping.
So from here how do you fix it? Easy—just let it dry out again and it will relax back to its normal shape. Turn it over so that the wet convex side is bowed out while the four corners of the cutting board rest on the counter. The drying process usually takes 24hrs if it’s minimal, however, severe warping of a thick board can take weeks to relieve. Leave it in a warm dry place with good airflow and your cutting board will be fixed in no time! It’s best practice to let it dry naturally rather than to artificially force it to dry faster even though it’s possible to speed things up. If you’re determined to speed things up do it gently.
How to make sure it never happens again - After washing your cutting board make sure to put it on its side so both large surfaces have contact with the air to dry. If you set it down flat, the cutting board will absorb moisture and prevent it from drying properly. In addition to proper drying, keeping it well oiled will help prevent warping. By oiling the wood you are filling in the pores and fibers, creating a light protective barrier. Plus a well oiled board looks so much better!