What type of surface finish is best for increasing durability of materials?

A varnish is the best choice for increasing the durability of materials, particularly wood. Varnishes are formulated to provide a tough, protective coating that enhances the lifespan of the surface by resisting moisture, UV radiation, and general wear and tear. The composition of varnish typically includes resins that polymerize to form a hard finish, offering superior protection compared to other options.

In contrast, paint serves primarily to provide color and aesthetic appeal, but while it offers some protection, it can wear away more easily and might not be as effective in environmental resistance as varnish. Stains are primarily designed to penetrate the surface and change the color of the material but do not create a protective film, which could lead to quicker deterioration of the wood or surface beneath. Lacquer can provide a hard finish as well, but it tends to be less durable than varnish, especially in terms of resistance to moisture and damage over time. Therefore, varnish stands out as the most effective finish for enhancing the durability of materials.