Wood Surface Preparation: A Step-by-Step Guide for the Perfect Oil Finish

An oil finish is the grand finale of your woodworking projects.

Oil finishes protect the wood surface, enhance its beauty, and draw out the depth of its grain.

However, no wood finish is going to give you everything you want unless you have taken the time to properly prepare the wood surface.

This guide is a quick reference for you to go from rough lumber to butter-smooth finished projects.

1. Wood Selection or identification

First, it is important to know what type of wood you are working with and its characteristics.

Some woods, like oak or walnut, have a grain structure that take oil finishes very well, while others can have larger or denser grain variations that can unevenly absorb oil, like maple. For woods with a tight grain, you may need to thin down your finish to achieve better surface penetration.

2. Sanding (and more sanding, and more sanding...and more sanding...)

Sanding may be the most important step in achieving the finish you want.

Because oil finishes do not build a thick film on the wood's surface, the texture of the wood when you are done sanding is very similar to the texture you are going to have when the project is complete.

We recommend starting with a low grit sandpaper, such as 80 or 100, depending on the starting texture of the wood. Sand in the direction of the grain. When finished with this grit, repeat with the next grit, working up to 220 grit for most finishes.

If you are working with a soft or open-pore wood, you may want to stop here.

If you are working with hardwoods, you may want to continue working up to 400 grit.

The important point to stop is before you have polished the surface.

The surface of the wood should not develop any gloss before you apply a finish.

If you go too far and develop a gloss through sanding, the pores of the wood will be closed off and will not be able to absorb the oil.

3. Water-pop the grain

When you are approaching your final grit, you will want to "water-pop" or raise the grain of the surface. This will result in the smoothest finish for oil finishes.

To do this, evenly spray the surface with water, or wipe it down with a damp rag.

Once you have allowed the surface to dry you should feel a slight texture when you run your hand over it. This is created by the cells of the wood swelling from absorbing the water.

Lightly sand the surface with your final grit to knock these back down. Ensure the effectiveness of this stage by repeating until you cannot feel any texture after dampening.

If you skip the step of raising the grain, your finish may cause these same cells to swell, resulting in a slightly textures, or "fuzzy" surface.

4. Clean off any dust

Use a vacuum with non-marking attachment to remove any dust from the surface of your project or use a tack cloth to wipe it down. This avoids trapping dust in your finish, resulting in a cleaner, more uniform finished surface.

5. Apply your oil finish

You are now ready to apply your oil finish!

For tightly grained woods, you may need to thin the first coat that you apply. You should be able to get guidance on this step from the manufacturer.

Grand Finishing's wood finishes, which you can find here, can be thinned with a gentle citrus solvent, such as d-limonene.

Happy woodworking! Reach out with any questions!