Trouble Shooting Wood Floor Finish Problems
Author: Terry Weinheimer (94 Articles)
Terry Weinheimer, resides in Oregon where he is a certified flooring inspector, floor covering consultant and educator.
As with the finishing of all types of products, a variety of problems can occur during the finishing of wood floors. With both factory applied finishes and site applied finishes the problem may be with the finish or a totally different cause. Here we discuss trouble shooting wood finish problems including some of the more common causes of finish problems. Additionally we offer some tips for solving them. Both manufacturing and site related conditions are discussed.
Adhesion
With an adhesion concern the coating is easily removed from the wood. Common causes include improper surface preparation, finishing over oil, grease or other contaminants, improper curing schedule, poor substrate integrity and incompatibility of one coat to another or to the substrate. The solutions for adhesion include ensuring a proper pretreatment; surface to be finished must be thoroughly clean and dry, adherence to a proper curing schedule and ensuring that the substrate has good integrity including proper sanding. The correction for an adhesion problem is replacement of damaged boards or sanding and refinishing as may be necessary. If the problem is caused by substrate integrity the problem may not be solved.
Alligatoring
Alligatoring is a condition in which the finish pulls away from itself, causing ridges in the finish, similar to an alligator’s skin. This condition can occur in both water-based and oil-modified finishes. There are many possible causes, including poor wetting of the finish, contamination of the finish, application under cold temperatures, application of a new coat before the previous coat has dried, application of a heavier coat than is recommended, or the use of thinners that cause the finish to dry too quickly. The solution is to screen and recoat after the finish has dried sufficiently.
Application Streaks
Application streaks are usually associated with water-based finishes. It often occurs when an improper spread rate is used – too much or too little finish is applied – or if the finish is not applied evenly. Excessive air movement and abnormally high temperatures can also be responsible for causing the finish to dry too quickly, so that a wet edge of finish is pulled over one that has already dried. The problem can also be caused by applying a satin or semi-gloss finish that has not been stirred properly. The solution is to screen and recoat after the finish has dried sufficiently.
Blistering
Blistering has the appearance of small swelled areas like a water blister on the human skin. Pinpoint holes in finish. Lack of gloss if blisters are minute. Broken edge craters if the blisters have burst. Blistering is caused by improper thinning solvent – too fast evaporating. Excessive film build trapped solvents. Additional causes on prefinished floors include excessive temperature in first oven zone. Insufficient flash off time before baking. Gasses entrapped in the substrate during the manufacturing process are forced out through the coating when baked at high temperatures. Solutions include reducing with slower evaporating solvents. Reduce film build. Reduce temperature in first oven zone. Increase flash off time prior to baking. Reduce overall oven temperature. The correction for blistering is to sand and refinish or replace blistered boards.
Crater (Fisheyes, Pitting)
Cratering gives the appearance of small crater-like depressions in the film. The more common causes of cratering include improper cleaning of the wood prior to finish application. Oil, water or other contaminants. Low film build. Overly wet application. Solutions for prevention include assuring that the surface to be finished is thoroughly clean and dry. Increase film build. Use proper maintenance to prevent contaminants. Eliminate contaminants from entering application areas. Corrections include replacement of cratered boards or sand and refinish as may be necessary.
Bleed Back
Bleed back is a condition associated with stain application. This condition occurs when excess stain seeps from the grain or from the spaces between boards. The most obvious cause is excessive stain application, but low-viscosity stain may also be the culprit. During application the solution is to wipe off the excess stain and let it dry thoroughly before applying another coat. If finish has already been applied over bleed-back, a complete resand is often required.
Brittleness
With brittleness the coating displays excessive rigidity and flakes off when scraped. The more common causes on a prefinished floor include over baking and excessive temperature and/or excessive time in the oven. Other common causes include excessive film build. Incompatibility of one coat to another or to substrate. Improper surface preparation. Solutions for brittleness include avoiding over baking. Reduce film build. Follow recommended practices using compatible materials and ensuring proper pretreatment.
Correction is to replace boards of concern or to sand and refinish.
Dirt
Dirt and foreign particles dried in the finish. The common causes for this include improper cleaning of the substrate, dirty work area or equipment. Solutions for prevention include assuring that the surface to be finished is thoroughly clean. Be sure all equipment is clean. Keep all finish containers closed to prevent contamination. In the plant ovens must also be kept clean. Corrections include screening and coating or sanding and refinishing as may be necessary.
Discoloration
Some finishes are amber in appearance and will yellow even further over time. Wood lying in direct sunlight will fade over time. These are natural changes – the former condition cannot be prevented, despite the pervasive myth that an oil-modified finish recoated with water-based finish will stop ambering. The latter condition can be prevented by shading the light source. Erratic discoloration can also occur – especially in white oak – if a good sealer is not used. This is called tannin pull.
Excessive and Early Wear
Excessive and early wear is often caused by improper maintenance procedures that have either failed to fully remove grit from the floor’s surface, or the introduction of water or strong cleaners. Dog nails, high heels and chair legs also contribute to the problem. Make sure the customer understands proper maintenance procedures, including regular dust-mopping with an approved wood-floor cleaner. (Some cleaners may leave a residue that will prevent good adhesion on a recoat.) If recoating is necessary, the owner should pay for it.
Lifting (Peeling)
With lifting their will be raising and sealing of the wet film or peeling when the surface is dry. Common causes of peeling include the improper curing of previous coating. Solvents in topcoat too strong. Application over improperly cleaned surfaces. Solutions for peeling include proper surface preparation. Be sure surface to be coated is properly cured. Use only recommended thinners. Correction includes the removal and replacement of damaged board or sanding and refinishing as necessary.
Orange Peel
If the surface of the finish has a texture that resembles an or- orange peel, the problem may have been caused by rolling a finish, which then dries too quickly. When that happens, the texture is “frozen” into place before the finish has a chance to flow out and level. The solution is to screen and re-coat.
Peeling, Bubbles, Blisters and Fish-Eyes
Any of these conditions can mean that the floor was not sufficiently screened between coats of finish, or that soap or some other contaminant substance was not removed before coating. It’s also possible that the affected coat is incompatible with the finish or stain previously applied, or a contaminated applicator may be responsible. Problems in the top-most finish coat can be screened and re-coated, although severe problems may require complete sanding and refinishing.
Pin Holes
Pin holes have the appearance of small swelled areas like a water blister on human skin. Broken edge craters if the blisters have burst. Lack of gloss if blisters are minute. Pin holes are caused by gasses entrapped in the substrate during the manufacturing process are forced out through the coating when baked at high temperatures. Other common causes of pin holes include moisture in finish during application, Improper thinning of solvent resulting in excessively fast evaporation, excessive film build up from trapped solvents. An additional cause on factory finished floor includes excessive temperature in the first oven zone and insufficient flash off time before baking. Solutions during site and factory application include reducing with slower evaporating solvents and reducing film build. For factory application addition solutions include the reduction of temperature in first oven zone. Increase flash off time prior to baking. Reduce overall oven temperature. The site related correction is to sand and refinish.
Solvent Popping
Solvent popping appears as small swelled areas like a water blister on the human skin, pinpoint holes in the finish, lack of gloss when the blisters are minute or broken edge craters if the blisters have burst. Gasses entrapped in the substrate during the manufacturing process are forced out through the coating when baked at high temperatures Solvent popping is caused by improper thinning solvent resulting in excessively rapid evaporation, excessive film build trapped solvents, excessive temperature in first oven zone, insufficient flash off time before baking. Solutions for solvent popping include reducing with slower evaporating solvents, reduction of film build, reduction of temperature in first oven zone, increase flash off time prior to baking and the reduction of the overall oven temperature. The correction for solvent popping is to sand and refinish.
Stains
Spilled water and other liquids, including the residue from incompatible cleaners, can stain finish. Cloudy surface finish can be fixed by lightly rubbing with a proper cleaner and buffing, although some stains require screening and recoating. Strong chemicals should not be used to remove stains.
Sticky Board Syndrome
This occurs when excessive tannic acid in the wood prevents the finish from adhering to the wood. This is most common with oil modified finishes and with white oak. When one board or several boards scattered throughout the floor will not take stain or finish, the only solution is to repair the floor by replacing the boards.
Uneven Gloss or Sheen Levels
Insufficient stirring of finish prior to application, a contaminated finish applicator and uneven sanding or finish thickness are typical culprits. All require rescreening an re-coating. Great care should be take if using different sheen levels. Sometimes, multiple coats of satin, three or more coats will start to give a hazing look to the finish coat.
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