What is the purpose of sealing wood when painting?

Sealing wood before painting primarily serves the purpose of protecting it against moisture. Unsealed wood is porous, which can allow moisture to penetrate and lead to issues such as warping, swelling, and decay. By applying a sealant, you create a barrier that reduces moisture absorption, thereby prolonging the wood's lifespan and maintaining its structural integrity. This is especially important for outdoor applications where wood is exposed to varying weather conditions.

While preventing splinters and improving aesthetics may be secondary benefits of sealing, they are not the primary reason for the practice. Sealing does not inherently contribute to a natural aging process; in fact, certain sealers are designed to prevent aging effects by blocking exposure to damaging elements. Therefore, the main goal remains to provide a protective layer that mitigates moisture-related damage.