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The Basics of Proper Wood Preparation

While it has often been said, it can't be over-emphasized: the better the wood preparation, the better the project. Wood finishing expert Bruce Johnson shares his tips to help you get off to a good start with your wood project.

Where to work

LOCATION

Choose a location to work on your wood project that won't be extremely busy. Curious pets, children and friends can accidentally leave fingerprints in your finish. Avoid areas that could be subject to dust. Select a spot where your wood project can be left undisturbed while each stage dries.

TEMPERATURE AND HUMIDITY

All wood finishing products depend on evaporation during the drying process. Low air temperatures and high relative humidity slow evaporation and increase the length of time your wood project will remain tacky. Before starting your wood project, make sure the temperature will remain above 65 degrees and the humidity around 50% during both application and the drying process.

VENTILATION

During the evaporation and drying process, all oil-based products emit fumes that need to be dispersed. If you are working indoors, set up a simple two-fan system: one fan draws fresh air into the room, while the other blows fumes out of the room. While water-based products are generally low odor, a similar ventilation system will insure that the products dry quickly.

Top 5 tips

INSPECT YOUR WOOD PROJECT.

Start by making a thorough inspection of the wood. Make note of any holes, cracks, splits or loose joints that need to be repaired. These are always best done prior to staining and finishing your wood project.

FILL HOLES AND CRACKS.

Small holes and cracks in the wood can be filled using Minwax® Stainable Wood Filler. Don't smear the wood filler around the hole, as that will require additional sanding to remove the excess. Instead, use the tip of a screwdriver to carefully pack the wood filler into the hole, mounding it slightly to allow for shrinkage as it dries.

STRENGTHEN ROTTED WOOD.

Old wood may have soft or rotted areas caused by excessive moisture. Scrape away any loose wood fibers, then brush on a liberal coat of Minwax® Wood Hardener. As it dries, it will harden and strengthen the softened wood. For exterior wood that will be painted, use Minwax® High Performance Wood Filler to replace any missing wood.

DON'T SKIP THE SANDING!

Sanding is a critical step in the wood preparation process for several reasons. It smooths out the dried Minwax® Stainable Wood Filler, Minwax® Wood Hardener or Minwax® High Performance Wood Filler, removes minor nicks and scratches, and opens the pores of the wood to accept more stain and finish. Sanding also removes the surface glaze created by the heat from the factory's planer blades as they come in contact with the natural resins in the wood. Left unsanded, this glaze can prevent stain or finish from entering the pores.

TEST, TEST, TEST.

Wood is unpredictable. Always test any technique, material or product on an inconspicuous spot before you proceed with the wood project.

Sanding in Wood Preparation.

Which one is right for you?

Minwax® Stainable Wood Filler.

Minwax® Stainable Wood Filler is great for filling small holes and cracks in the wood. It is specially formulated to accept Minwax® wood stains.

Minwax® High Performance Wood Filler.

Minwax® High Performance Wood Filler is used to fill gouges and holes in split, damaged, or rotted exterior and interior wood that will be painted.

Minwax® High Performance Wood Hardener.

Minwax® High Performance Wood Hardener will strengthen and reinforce decayed or rotting areas, resulting in a hardened wood surface.

Sanding tips

CHOOSING THE RIGHT SANDPAPER.

Sandpaper is produced in various degrees of coarseness, measured by 'grits.'

  • Sandpaper below #100-grit is only used to quickly remove wood or layers of an old floor finish. It is most often used when refinishing floors or refitting doors and windows.
  • Medium sandpaper (#100-grit and #120-grit) is ideal for removing shallow scratches, dents, and rough edges that could cause splinters. Either of these two grits is often used for a first sanding of most wood projects.
  • Medium-fine sandpaper (#180-grit and #220-grit) is used for a second sanding. It will remove any scratches left by the medium sandpaper and will eliminate any remaining loose fibers in the wood. After this second sanding, the wood is ready for a stain or finishing product to be applied.

CAPTURING DUST.

Dust is the enemy of a smooth finish. Blowing sanding dust off your wood project with an air compressor or brushing it onto your floor can still result in it ending up in your wet stain or finish. Instead, use a bristle attachment on a vacuum to safely capture it once and for all.

CHOOSING THE RIGHT SANDER.

For small, intricate wood projects, hand-sanding is best. Tear or cut a sheet of sandpaper into fourths, then fold each piece until it fits comfortably beneath three fingers of your hand. For large, flat surfaces, an electric orbital or palm sander can also be used, although it is not required. You can also wrap your sandpaper around a scrap piece of wood for flat surfaces. Powerful belt sanders, however, can do more damage than good on any project wood other than floors. They generally create more scratches than they erase.

The right sander for Wood Preparation.

Choosing a pre-stain conditioner

Wood rarely absorbs stain evenly. The various sizes of pores account for the difference in the amount of stain one board or even one section of a board will absorb compared to another. To minimize this difference and to reduce the blotchiness that often occurs when staining, brush on a coat of Minwax® Pre-Stain Wood Conditioner after vacuuming off the sanding dust, but before you apply your stain.

Wood sample without a pre-stain conditioner.

Without Pre-Stain Conditioner

Wood sample with a pre-stain conditioner.

With Pre-Stain Conditioner

Minwax® Pre-Stain Wood Conditioner.
Minwax® Water Based Pre-Stain Wood Conditioner

Minwax® Pre-Stain Wood Conditioner is available as either a water-based or an oil-based formulation.

When making your decision, consider the following:

Oil and water don't mix.

Your wood conditioner and stain should be either all water-based or oil-based on each wood project.

Water-based products offer unique ease-of-use benefits.

They dry faster than oil-based products and are low odor. Clean-up for water-based products can be done using soap and water, while mineral spirits or paint thinner are needed for oil-based products.

Water-based wood conditioner will cause the wood fibers to swell slightly.

After the wood conditioner dries, lightly sand the wood with #180-grit sandpaper to smooth out the raised grain.

When to use a sanding sealer

A sanding sealer is not the same as a wood conditioner. Whereas a wood conditioner is a pre-stain treatment that reduces blotchiness when staining, a sanding sealer is applied only to bare wood that is not going to be stained. A sanding sealer can be used on bare, unstained floors, doors, furniture and cabinets prior to applying either an oil-based or a water-based clear finish. It is designed as a base coat that will dry quickly, seal the pores, and sand easily with fine sandpaper to create an ultra-smooth foundation.

Minwax® offers two different sanding sealers:

Minwax® Professional Formula Sanding Sealer

Minwax® Professional Formula Sanding Sealer can be used prior to any Minwax® oil-based or water-based polyurethane finish.

Minwax® Lacquer Sanding Sealer

Minwax® Lacquer Sanding Sealer is designed to only be used on raw, unstained wood that will then be finished with Minwax® Clear Brushing Lacquer.

Wood Preparation Do's and Don'ts

DO…

Make sure your wood project and wood preparation products are at room temperature before starting. Like the air in your work area, both the wood surface and any wood preparation product you are using should be above 65 degrees. Let them sit at room temperature overnight before starting your wood project.

Keep the temperature in your work area above 65 degrees during the entire recommended drying time listed on the label. If the temperature drops, the evaporation process will slow and the wood preparation product will remain tacky for a longer length of time.

Always sand in the same direction the grain 'runs' down a board. Sanding against the grain leaves scratches that will become painfully obvious when they later absorb either stain or finish.

Apply extra Minwax® Pre-Stain Wood Conditioner on the end grain of any board to prevent it from absorbing more stain than the flat sides of the board.

DON'T…

Work in strong, direct sunlight. The heat from the sun can cause moisture in the wood to create bubbles in your stain or finish.

Work beneath heating or air conditioning vents that can blow dust directly into your wet finish.

Use a belt sander on anything other than a floor, as it can quickly leave deep gouges and scratches in the wood.

Skip the wood conditioner on projects you are going to stain. The wood conditioner improves the appearance of any stained wood.