Proper Preparation Procedures for Finishing Wood


Finishing related problems associated with wood. Of all the wood related finishing problems I’ve dealt with, investigated, or inspected over the years, 95% are caused by inadequate wood preparation prior to finishing. The remaining five percent are caused by inexperienced painter-finishers, poor finishing conditions, or unsuitable finishing procedures or products.

Percentage breakdown. Let’s break down the finishing system by percentages: preparation should take 30% of the time spent on the project, stain application and sealing should take 30%, and top coating and sanding between coats should take 30%. That leaves 10% of the project time for protection prior to and after finishing. These are standard percentages used in the wood finishing industry. However, custom projects with special finishes or painting may require a different approach.

Responsibility. It is the painter-finisher’s responsibility to understand the characteristics of the wood he or she is about to finish and properly prepare the wood prior to finishing. Be warned: if proper preparation procedures are not followed, the final look and performance of the finished woodwork will not be of a premium level and might be rejected.

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■ Proper Preparation Procedures for Finishing Wood ■ Types of Finishes ■ Things to Consider Before Preparation Begins
■ Basic Wood Preparation Procedures for Finishing

Solutions to Common Wood Finishing Problems

1. Water spots. When wood gets wet, the grain will raise, open, or puff up in the area where the water touched the wood. This will cause the wood to absorb stain more readily in that area than the other areas of the wood. Thus, stains will become darker and natural finishes will puff up.

Solving this problem is very simple. The first method is to spot san the area, then re-sand the entire surface. The second method is an old finisher’s trick. Mix a 25/75 formula of lukewarm water with alcohol and apply this evenly to the entire wood surface. Let the wood dry and then surface sand the entire piece. Make sure you double-check the moisture content before finishing.

2. Blotchy finish or barber-pole. I’m not a big fan of pre-sealers, except in special cases. Most plywood manufactured today is well made and has been precision cut and sanded. If the painter-finisher is experienced, they will know how the wood will accept their stain and finish and whether or not they should pre-seal. Stains can be adjusted and applied in ways to eliminate almost all pre-sealing situations. However, sometimes pre-sealing is the only option and should be done.

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■ Solutions to Common Wood Finishing Problems
■ Situations That May Require Pre-Sealers