

Also, a fine acoustic guitar will have a very slight arch in the back and front. (About 1/16 - 1/8") That means that if there is some movement in the wood because of humidity, that movement tends to increase or decrease the arch, rather than splitting the wood apart.
This is the way. Waxes, oils, and even shellac are not durable finishes that will hold up under the kind of wear a desk top will be subjected to.