It's all in the preparation
The secret to a perfect finish is to sand the surface prior to finishing. The more care taken with preparation, the more finish will penetrate the wood, providing an even, consistent and long-lasting finish. Studies have proven sanding can extend the life of a finish by up to 3 times compared to an unsanded surface.
What does sanding do?
Remove mill glaze
Mill glaze occurs when heat from the milling and kiln drying processes bring water soluble extractives to the surface, causing a glaze-like finish to form. Mill glaze can be removed wih a simple sand, allowing the pores underneath to breathe again and accept finish more readily.
Create an even surface
Sanding takes away any small differences in surface texture which may not be visible at first glance. It stands to reason that an uneven surface will pick up finish in some areas more than others. An unsanded texture will also be exposed to more traffic in certain areas and will collect dirt and moisture in ingresses. Sanding will create a smooth and flat surface allowing finish to penetrate consistently across the surface area and withstand footfall much more evenly.
Along with removing the mill glaze, excess fibre and uneven surface, sanding opens up the pores of the wood, allowing finish to penetrate deeper into the cell structure of the wood.