During Application
Crack Beading or Poly BB's
The Cause
Most finishes and stains dry from the top down. When the first coat is applied, whether it is a stain or finish, it seeps down into the cracks between the boards. The material therefore stays comparatively wet because there is no air movement. Usually, at this point three things happen:
- Additional coats are applied
- The floor is covered
- Time elapses
As additional coats are applied, the problem is compounded. Then covering the floor may affect the dry time by locking the solvents down in the cracks. In time the floor expands and contracts. Expansion pushes the boards together and the still wet material down in the gaps is squeezed up, forming the beads.
How to fix the problem
It has to be understood that this is NOT a finish problem. How to know? The finish looks great on the face of the boards for all coats; the only issue is the cracks.
The solution to the problem is time. Allow the floor to expand and contract and just keep removing the beads that have cured or hardened with a putty knife or scraper. DO NOT attempt to screen the beads off, this will cause circular scratches in the surface of the finish. If there are bb's that are still soft, remove them with a scraper then wipe the area with a rag dampened with mineral spirits.
How to avoid in the future
Apply the sealer, stain and or finish as per manufacturer's recommended instructions using the correct coverage rate. Remember more is not better. Watch for excessive cracks. These can be trowel-filled (as per manufacturer's instructions) Also pay attention to the factors that affect dry time. Floors should be installed at normal living conditions. That means with all windows and doors in place, all wet trades done and the HVAC system running. It is important to control the job site environment. Avoid high relative humidity, above 90% R.H. and lower temperatures below 50 degrees F (10 C) that can seriously slow the drying time of sealers, stains and finishes.
Once the floor is finished, allow it to cure appropriately before covering. Check the manufacturer's technical sheets for correct dry times.
Finish Drying Too Fast
The Problem
Finish Drying too fast.
The Cause
Most finishes will dry too fast in high temperatures, above 90 degrees F. (32 C.) and low humidity (under 30% relative humidity). A combination of both makes much worse. Also direct airflow across the surface will cause the finish to dry too fast.
How to fix the problem
Determine which of the above is the cause of the problem. Lower the temperature and/or increase the humidity. Remember to STOP the A/C 30 minutes prior to application. Re-start when product tacks over, usually about one hour, dependent on waterbased or oil-based formula usage.
How to avoid in the future
A simple tool such as a hygrometer will tell you what the job site condition is and therefore you have the opportunity to act accordingly. DuraSeal® recommends changing your expectation of the dry time if your application and drying conditions vary from...
- The coverage rate on the label (see Finish and Curing Parameters)
- A temperature above 70 degree F (25 C) and Relative Humidity below 50%.
Note: Dry times, either fast or slow, are affected by Temperature, Relative Humidity and Air movement, either natural (window) or forced (HVAC) PLUS coverage rate. Attention to these details improves success rates.
Finish Won't Dry
The Problem
Finish drying too slow.
The Cause
Air/product temperature at or below 50 degrees F. (10 C) and relative humidity over 90% and/or covering the floor with brown paper or cardboard before it's dry will cause slower dry times. (A combination of both makes conditions worse) All of these points prevent the solvent from leaving the wet film. Contaminants in the grain or between the boards can also be the cause for slow dry. Additionally, some globally resourced exotic hardwoods may not be compatible with certain finish types. Consult your hardwood flooring distributor for specific species of concern.
How to fix the problem
Determine which of the above, or combination of, is the cause of the problem.
Remember to stop the A/C (close windows and doors) 30 minuntes prior to application. Then re-start (reopen) when the finish is tack free. This usually occurs after about one to two hours for oil modified polyurethane, and 15 to 20 minutes for waterbased products. After these corrections to the site conditions have been made, the main ingredient is time. DO NOT attempt to screen the floor until the finish has completely dried since this will cause deep scratches in the finish and will remain visible. You could also experience solvent entrapment, causing a tender topcoat, which is a cause of early wear. A complete re-sand is the alternative.
How to avoid in the future
A simple tool such as a hygrometer will tell you what the job site condition is and therefore you have the opportunity to act accordingly. DuraSeal® recommends changing your expectation of the dry time if your application and drying conditions vary from...
- The coverage rate on the label (see Finish and Curing Parameters)
- A temperature above 70 degree F (25 C) and Relative Humidity below 50%.
Note: Dry times, either fast or slow, are affected by Temperature, Relative Humidity and Air movement, either natural (window) or forced (HVAC) PLUS coverage rate. Attention to these details improves success rates.
Bubbles and Craters
The Problem
Topcoat has bumps when dry.
The Cause
Bubbles
This can be the result of the finish or the floor being too cold, humidity being too high, the previous coat(s) not being dry before this last coat was applied, or overworking the finish during application. In addition, not following the coverage rate directions such as applying too heavy a coat, often lead to this condition. Most finishes cure from the top down. If the wet coat forms a skin before the air folded into it can escape, the finish forms bubbles and can not level out.
Craters
These are caused by bubbles that have released their air but the finish has then hardened to a point that it can not level out and feels rough to the touch.
Trash in the Finish
Airborne dust from heating vents and/or failure to tack efficiently, place dust particles in the finish. Also an aged, partially-used container of finish may contain skinned product which may be distributed throughout the product upon agitation.
How to fix the problem
Oil modified bubbles and craters can usually be screened and re-coated with a thin coat of finish. Waterbased finishes that have bubbled can be scraped flat but will probably require re-sanding.
How to avoid in the future
Determining the conditions at the job site and ensuring that it is feasible to apply the finish is the responsibility of professional sand and finishers. Tools such as hygrometers and moisture meters tell you what the job site conditions are so that you can act accordingly. Where possible alter the temperature, humidity and ventilation conditions to those recommended by the specific product directions. Block off all air vents, sweep, vacuum, and tack, then apply finish.
If this is not possible to do immediately, it is better to wait until you can.
Uneven Color
The Problem
The look of the stain is uneven.
The Cause
This can be due to the sanding procedures being uneven. Uneven sanding will cause the color to look uneven. Improper wiping techniques are another reason for uneven staining.
How to fix the problem
- If sanding procedures are the cause, then only a complete re-sanding and re-staining of the floor will fix the problem.
- If improper wiping techniques are the reason for uneven staining, and the floor has not yet been top coated, buffing the floor with mineral spirits and steel wool (for solvent-based finishing systems only), or white synthetic pad under the buffer, will even out the color.
How to avoid in the future
Sand the floor according to NWFA standards. Ensure ALL superfluous stain is wiped from the floor.
Wrinkling, Alligatoring or Blistering
The Problem
Topcoat is not smooth when dry.
The Cause
This can be the result of the bottom coat(s) not being dry enough to accept an additional coat. Or, a topcoat's solvents etches (eats) into weaker or uncured bottom coats. The job site conditions and too heavy a first coat are the usual reason for these problems.
Blistering
Will sometimes occur in spots and could be caused by spotty drying of bottom coats.
Wrinkling
Will result as blisters over a large area of the floor.
Alligatoring
Very heavy wrinkling results when the topcoat etches (eats) into the bottom coat and actually lifts it from the raw wood or the stain or sealer.
How to fix the problem
Blistering and wrinkling can usually be screened and coated with a very thin coat of finish. Alligatoring requires a complete sand and re-coat.
How to avoid in the future
Determining the conditions at the job site and ensuring that it is practical to apply stains and finishes is the first duty of professional sand and finishers. Tools such as hygrometers and moisture meters tell you what the job site conditions are so that you can act accordingly. Should the conditions be borderline, it is wise to allow more time than normal to ensure the sealer, stain or finish is dry. Correct temperature, humidity and ventilation are the keys to avoiding these problems. In addition, not following the coverage rate directions such as applying too heavy a coat, often lead to this condition.